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Gynecology_Novak. 28. Thompson S. Clinical risk management in obstetrics: eclampsia drills. BMJ 2004;328:269–271. 29. Crofts JF, Bartlett C, Ellis D, et al. Management of shoulder dystocia: skill retention 6 and 12 months after training. Obstet Gynecol 2007;110:1069–1074. 30. Institute for Healthcare Improvement. http://www.ihi.org/ IHI/Topics/PatientSafety/MedicationSystems/Changes/Individual Changes/Conduct+Adverse+Drug+Event+%28ADE%29+Drills.htm. 31. World Health Organization. Prevention of hospital acquired infections: a practical guide. Geneva, Switzerland: World Health Organization Department of Communicable Disease, Surveillance and Response, 2002. 32. Coella R, Glenister H, Fereres J, et al. The cost of infection in surgical patients: a case study. J Hosp Infect 1993;25:239–250. 33. Mangram AJ, Horan TC, Pearson ML, et al. Guideline for prevention of surgical site infection, 1999. Centers for Disease Control and Prevention; U.S. Public Health Service, Atlanta, GA, 1999. 34.


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Gynecology_Novak. Mangram AJ, Horan TC, Pearson ML, et al. Guideline for prevention of surgical site infection, 1999. Centers for Disease Control and Prevention; U.S. Public Health Service, Atlanta, GA, 1999. 34. Nuland S. The doctors’ plague: germs, childbed fever, and the strange story of Ignac Semmelweis. New York: Norton, 2004. 35. Centers for Disease Control and Prevention. Guideline for hand hygiene in the health care settings. MMWR Morb Mortal Wkly Rep 2002;51:RR-16. 36. Siegel JD, Rhinehart E, Jackson M, et al. 2007 Guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings. Centers for Disease Control and Prevention, Atlanta, GA, 2007. 37. Serious reportable events. National Quality Forum Fact Sheet. October 2008. http://qualityforum.org/Publications/2008/10/Serious Reportable Events.aspx 38. Statement on ensuring correct patient, correct site, and correct procedure surgery. Bull Am Coll Surg 2002;87:12. 39.


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Gynecology_Novak. Reportable Events.aspx 38. Statement on ensuring correct patient, correct site, and correct procedure surgery. Bull Am Coll Surg 2002;87:12. 39. The Joint Commission. Universal protocol. Available online at: http://www.jointcommission.org/standards in formation/up.aspx 40. Gawande A. The checklist manifesto: how to get things right.New York: Metropolitan Books, 2009. 41. Pronovost P, Needham D, Berenholtz S, et al. An intervention to decrease catheter-related bloodstream infections in the ICU. N Engl J Med 2006;355:2725–2732. 42. Gawande A. The checklist. New Yorker, December 10, 2007. 43. World Health Organization. Guidelines for safe surgery. 2009. http:// whqlibdoc.who.int/publications/2009/9789241598552 eng.pdf 44. Haynes AB, Weiser TG, Berry WR, et al. Surgical safety checklist to reduce morbidity and mortality in a global population. N Engl J Med 2009;360:491–499. 45.


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Gynecology_Novak. Haynes AB, Weiser TG, Berry WR, et al. Surgical safety checklist to reduce morbidity and mortality in a global population. N Engl J Med 2009;360:491–499. 45. Gawande AA, Studdert DM, Orav EJ, et al. Risk factors for retained instruments and sponges after surgery. N Engl J Med 2003;348:229– 235. 46. Statement on the prevention of retained foreign bodies after surgery. Bull Am Coll Surg 2005;90:10. http://www.facs.org/fellows info/statements/st-51.html 47. Gibbs VC, Auerbach AD. The retained surgical sponge. In: Shojania KG, Duncan BW, McDonald KM, Wachter RM, eds. Making health care safer: a critical analysis of patient safety practices. Evidence Report/Technology Assessment No. 43. AHRQ Publication No. 01-E058. 2001. Washington, DC. http://archive.ahrq.gov/clinic/ ptsafety/summary.htm 48. No Thing Left Behind®. A national surgical patient-safety project to prevent retained surgical items. Available online at: www. nothingleftbehind.org. 49.


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Gynecology_Novak. No Thing Left Behind®. A national surgical patient-safety project to prevent retained surgical items. Available online at: www. nothingleftbehind.org. 49. Rogers A. Radio frequency identification (RFID) applied to surgical sponges. Surg Endosc 2007;21:1235–1237. 50. King WJ, Paice N, Jagadish R, et al. The effect of computerized physician order entry on medication errors and adverse drug events in pediatric patients. Pediatrics 2003;112:506–509. 51. Paparella S. Avoiding dangerous abbreviations and dose expressions. J Emerg Nurs 2004;30:54–58. 52. Reiter RC, Yielding L, Gluck PA. Clinical performance improvement: assessing the quality and safety of women’s health care. In: Hacker NF, Moore JG, Gambone JC, eds. Essentials of obstetrics and gynecology, 4th ed. Philadelphia: Elsevier/Saunders, 2004:50– 51. 53. Gluck PA. Physician leadership: essential in creating a culture of safety. Clin Obstet Gynecol 2010;53:473–481. 54.


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Gynecology_Novak. 53. Gluck PA. Physician leadership: essential in creating a culture of safety. Clin Obstet Gynecol 2010;53:473–481. 54. The Joint Commission. Speak-up program. 2010. Available online at: http://www.JointCommission.org/generalpublic/speak+up/about speakup.htm 55. DiMatteo RM, Reiter RC, Gambone JC. Enhancing medication adherence through communication and informed collaborative choice. Health Commun 1994;6:253–255. 56. LeGros N, Pindall JD. Active disclosure of unanticipated adverse events. Health Law 2002;35:189–210. 57. Kachalia A, Kaufman SR, Boothman R, et al. Liability costs before and after implementation of a medical error disclosure program. Ann Intern Med 2010;153:213–221. 58. Leape LL. Full disclosure and apology—an idea whose time has come. Physician Exec 2006;32:16–18. 59. Liebman CB, Hyman CS. A mediation skills model to manage disclosure of errors and adverse events to patients. Health Affairs 2004;23:22–32. 60.


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Gynecology_Novak. 59. Liebman CB, Hyman CS. A mediation skills model to manage disclosure of errors and adverse events to patients. Health Affairs 2004;23:22–32. 60. The Sorry Works Coalition. Available online at: www.sorryworks.net 61. American College of Obstetricians and Gynecologists. Report of the Presidential Task Force on Patient Safety in the office setting. Washington, DC: ACOG, 2010. 62. Erickson, TB, Kirkpatrick DH, DeFrancesco MS, et al. Executive summary of the American College of Obstetricians and Gynecologists Presidential Task Force on Patient Safety in the office setting. Obstet Gynecol 2010;115:147–151. 63. Casalino L. Markets and medicine: barriers to creating a “business case for quality.” Perspect Biol Med 2003;46:38–55. 64. Berwick DM, Nolan TW. Physicians as leaders in improving health care: a new series in Annals of Internal Medicine. Ann Intern Med 1998;128(4):289–292. 65.


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Gynecology_Novak. 64. Berwick DM, Nolan TW. Physicians as leaders in improving health care: a new series in Annals of Internal Medicine. Ann Intern Med 1998;128(4):289–292. 65. James B. Cost of poor quality or waste in integrated delivery system settings. Appendix A: quality and inefficiency waste in the peer-reviewed medical literature. 2010. U.S. Department of Health and Human Services. Agency for Healthcare Research and Quality. Available online at: http://www.ahrq.gov/research/costpqids/cpqidsappa. 66. Weeks WB. Higher health care quality and bigger savings found at large multispecialty medical groups. Health Aff 2010;29:991–997. 67. Greenberg, Michael D, Amelia M. Haviland, J. Scott Ashwood and Regan Main. Is Better Patient Safety Associated with Less Malpractice Activity? Evidence from California. Santa Monica, CA: RAND Corporation, 2010. http://www.rand.org/pubs/technical reports/TR824. Maureen G. Phipps Daniel W. Cramer


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Gynecology_Novak. CA: RAND Corporation, 2010. http://www.rand.org/pubs/technical reports/TR824. Maureen G. Phipps Daniel W. Cramer Clinical research includes a range of research disciplines and approaches, including patient-oriented research, clinical trials, epidemiology, and outcomes research. Patient-oriented research centers on understanding mechanisms of human disease, studies of therapies, or interventions for disease. Clinical trials use a controlled experimental design to assess the effectiveness of an intervention on an outcome. Epidemiology is the study of the distribution and determinants of health and disease in specific populations. Outcomes research and health services research include studies that seek to identify the most effective and efficient intervention, treatments, and services for patient care.


Gynecology_Novak

Gynecology_Novak. Outcomes research and health services research include studies that seek to identify the most effective and efficient intervention, treatments, and services for patient care. Study designs include experimental studies (clinical trials), observational studies (cohort studies, case-control studies, and cross-sectional studies), and descriptive studies (case reports and case series). Scientific validity of a research study is evaluated by understanding the study question, how the study was designed, and whether chance, bias, or confounding could have accounted for the findings.


Gynecology_Novak

Gynecology_Novak. Scientific validity of a research study is evaluated by understanding the study question, how the study was designed, and whether chance, bias, or confounding could have accounted for the findings. Medical practice is evolving to include complex options for patient treatment and preventive care, in part because clinical research methods and techniques to guide patient care have advanced. To evaluate whether new treatments and diagnostic approaches should be integrated into clinical practice or decide whether observational data reported in the literature is relevant, clinicians should understand the fundamental strengths and limitations of clinical research methods and the level of evidence different types of studies provide.


Gynecology_Novak

Gynecology_Novak. As outlined by the National Institute of Child Health and Human Development, clinical research includes patient-oriented research involving understanding mechanisms of human disease, studies of therapies or interventions for disease, clinical trials, and technology development. Epidemiologic methods and behavioral research are used in clinical research to examine the distribution of disease and the factors that affect health and how people make health-related decisions. Outcomes research and health services research include studies that seek to identify the most effective and efficient intervention, treatments, and services for patient care (1). The purpose of a research study is to test a hypothesis about and to measure an association between exposure (or treatment) and disease occurrence (or prevention). The type of study design inﬂuences the way the study results should be interpreted.


Gynecology_Novak

Gynecology_Novak. Analytic studies are often subdivided into experimental studies (clinical trials) and observational studies (cohort studies, case-control studies, and cross-sectional studies). Descriptive studies (case reports and case series) often provide useful information for informing future analytic studies. The common types of clinical research study methods, considerations for the strength of evidence for the specific study design, and interpretation of the results are presented. Although there is debate about which system should be used for evaluating the strength of evidence from an individual study, a well-designed and executed clinical trial presents the highest level of evidence (2). Other types of studies should be designed to best approach the strengths of a clinical trial.


Gynecology_Novak

Gynecology_Novak. Clinical Trials Clinical trials include intervention studies where the assignment to the treatment or control condition is controlled by the investigator and the outcomes to be measured are clearly defined at the time the trial is designed. Features of randomized clinical trials include randomization (in which participants are randomly assigned to exposures), unbiased assessment of outcome, and analysis of all participants based on the assigned exposure (an “intention to treat” analysis). There are many different types of clinical trials, including studies designed to evaluate treatments, prevention techniques, community interventions, quality-of-life improvements, and diagnostic or screening approaches (3). Since 2007, investigators conducting randomized clinical trials are expected to register the trial to comply with mandatory registration and results reporting requirements (4).


Gynecology_Novak

Gynecology_Novak. Clinical Trial Phases New investigational drugs or treatments are usually evaluated by clinical trials in phases with more people being involved as the purpose of the study becomes more inclusive (3). Phase I Trials In these trials, researchers test an experimental drug or treatment for the first time in a small group of people (20–80) to evaluate its safety, determine a safe dosage range, and identify side effects. Phase II Trials In these, the experimental study drug or treatment is given to a larger group of people (100–300) to see whether it is effective and to further evaluate its safety. Phase III Trials In phase III trials, the experimental study drug or treatment is given to large groups of people (1,000–3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.


Gynecology_Novak

Gynecology_Novak. Phase IV Trials These are postmarketing studies that delineate additional information, including the drug’s risks, benefits, and optimal use. the factors that might inﬂuence outcome, such as age, stage of disease, medical history, and symptoms, are similar in patients assigned to the study protocol compared with patients assigned to placebo or traditional treatment. Published reports from the clinical trial are expected to include a table showing a comparison of the treatment groups with respect to potential confounders and to demonstrate that the groups did not differ in any important ways before the study began.


Gynecology_Novak

Gynecology_Novak. CONSORT Checklist Clearly defining the outcome or criteria for successful treatment helps ensure unbiased assessment of the outcome. A well-designed clinical trial has a sufficient number of subjects enrolled to ensure that a “negative” study (one that does not show an effect of the treatment) has enough statistical power to evaluate the predetermined (a priori), expected treatment effect. The Consolidated Standards of Reporting Trials (CONSORT) Statement is an evidence-based, minimum set of recommendations for reporting on randomized controlled trials developed by the CONSORT Group to alleviate the problems arising from inadequate reporting of randomized controlled trials. The 25-item CONSORT checklist (Table. 4.1) and ﬂow diagram Table 4.1 CONSORT Checklist Item Reported on Section/Topic No. Checklist Item Page No.


Gynecology_Novak

Gynecology_Novak. Table 4.1 CONSORT Checklist Item Reported on Section/Topic No. Checklist Item Page No. 1a Identification as a randomized trial in the title 1b Structured summary of trial design, methods, results, and conclusions (for specific guidance see CONSORT for abstracts)∗ Background and 2a Scientific background and explanation of rationale objectives 2b Specific objectives or hypotheses


Gynecology_Novak

Gynecology_Novak. Background and 2a Scientific background and explanation of rationale objectives 2b Specific objectives or hypotheses Trial design 3a Description of trial design (such as parallel, factorial) including allocation ratio 3b Important changes to methods after trial commencement (such as eligibility criteria), with reasons Participants 4a Eligibility criteria for participants 4b Settings and locations where the data were collected Interventions 5 The interventions for each group with sufficient details to allow replication, including how and when they were actually administered Outcomes 6a Completely defined prespecified primary and secondary outcome measures, including how and when they were assessed 6b Any changes to trial outcomes after the trial commenced, with reasons Sample size 7a How sample size was determined 7b When applicable, explanation of any interim analyses and stopping guidelines


Gynecology_Novak

Gynecology_Novak. Randomization: sequence generation 8a Method used to generate the random allocation sequence 8b Type of randomization; details of any restriction (such as blocking and block size) Allocation concealment 9 Mechanism used to implement the random allocation sequence (such mechanism as sequentially numbered containers), describing any steps taken to conceal the sequence until interventions were assigned Implementation 10 Who generated the random allocation sequence, who enrolled participants, and who assigned participants to interventions Blinding 11a If done, who was blinded after assignment to interventions (for example, participants, care providers, those assessing outcomes) and how 11b If relevant, description of the similarity of interventions Statistical methods 12a Statistical methods used to compare groups for primary and secondary outcomes 12b Methods for additional analyses, such as subgroup analyses and adjusted analyses Table 4.1 CONSORT Checklist (Continued ).


Gynecology_Novak

Gynecology_Novak. Table 4.1 CONSORT Checklist (Continued ). Item Reported on Section/Topic No. Checklist Item Page No.


Gynecology_Novak

Gynecology_Novak. Participant ﬂow 13a For each group, the numbers of participants who were randomly (a diagram is strongly assigned, received intended treatment, and were analyzed for the recommended) primary outcome 13b For each group, losses and exclusions after randomization, together with reasons Recruitment 14a Dates defining the periods of recruitment and follow-up 14b Why the trial ended or was stopped Baseline data 15 A table showing baseline demographic and clinical characteristics for each group Numbers analyzed 16 For each group, number of participants (denominator) included in each analysis and whether the analysis was by original assigned groups Outcomes and 17a For each primary and secondary outcome, results for each group, and estimation the estimated effect size and its precision (such as: 95% confidence interval) 17b For binary outcomes, presentation of both absolute and relative effect sizes is recommended Ancillary analyses 18 Results of any other analyses performed, including


Gynecology_Novak

Gynecology_Novak. as: 95% confidence interval) 17b For binary outcomes, presentation of both absolute and relative effect sizes is recommended Ancillary analyses 18 Results of any other analyses performed, including subgroup analyses and adjusted analyses, distinguishing prespecified from exploratory Harms 19 All important harms or unintended effects in each group (for specific guidance see CONSORT for harms)∗


Gynecology_Novak

Gynecology_Novak. Limitations 20 Trial limitations, addressing sources of potential bias, imprecision, and, if relevant, multiplicity of analyses Generalizability 21 Generalizability (external validity, applicability) of the trial findings Interpretation 22 Interpretation consistent with results, balancing benefits and harms, and considering other relevant evidence Registration 23 Registration number and name of trial registry Protocol 24 Where the full trial protocol can be accessed, if available


Gynecology_Novak

Gynecology_Novak. Registration 23 Registration number and name of trial registry Protocol 24 Where the full trial protocol can be accessed, if available Funding 25 Sources of f funding and other support (such as supply of drugs), role of funders *We strongly reconmiend reading this statement in conjunction with the CONSORT 2010 Explanation and Elaboration for important clarifications on all the items. If relevant, we also recommend reading CONSORT extensions for cluster randomized trials, nonlnferiority and equivalence trials, nonpharmacological treatments, herbal interventions, and pragmatic trials. Additional extensions are forthcoming: for those and for up-to-date references relevant to this checklist, see www.consort-statement.org. (Fig. 4.1) offer a standard way for authors to prepare reports of trial findings, facilitating their complete and transparent reporting and aiding their critical appraisal and interpretation (5).


Gynecology_Novak

Gynecology_Novak. (Fig. 4.1) offer a standard way for authors to prepare reports of trial findings, facilitating their complete and transparent reporting and aiding their critical appraisal and interpretation (5). Clinical trials are considered a gold standard, because when done well they provide information about both relative and absolute risks and minimize concerns about bias and confounding (see the section on Presenting and Understanding the Results of Analytic Studies). Many clinical research questions are not amenable to clinical trials because of cost restraints, length of time required to complete the study, and feasibility of recruitment and implementation.


Gynecology_Novak

Gynecology_Novak. When evaluating the results from a clinical trial, consider how restrictive inclusion and exclusion criteria may narrow the participant population to such a degree that there may be concerns about external validity or generalizing the results. Other concerns include blinding, loss to follow-up, and clearly defining the outcome of interest. When the results of a randomized controlled trial do not show a significant effect of the treatment or intervention, the methods should be evaluated to understand what assumptions (expected power and effect size) were made to determine the necessary sample size for the study. Allocated to intervention (n = )  Declined to participate (n = ) Allocated to intervention (n = )


Gynecology_Novak

Gynecology_Novak. Allocated to intervention (n = )  Declined to participate (n = ) Allocated to intervention (n = ) Analyzed (n = )  Excluded from analysis (give reasons) (n = ) Lost to follow-up (give reasons) (n = ) Discontinued intervention (give reasons (n = ) Analyzed (n = )  Excluded from analysis (give reasons) (n = ) Lost to follow-up (give reasons) (n = ) Discontinued intervention (give reasons (n = ) Analysis Figure 4.1 CONSORT ﬂow diagram.


Gynecology_Novak

Gynecology_Novak. Figure 4.1 CONSORT ﬂow diagram. Randomized controlled trials should be evaluated with an intention-to-treat analysis, which means that all of the people randomized at the initiation of the trial should be accounted for in the analysis with the group to which they were assigned. Unless part of the overall study design, even if a participant stopped participating in the assigned treatment or “crossed over” to another treatment during the study, they should be analyzed with the group to which they were initially assigned. All of these considerations help to minimize bias in the design, implementation, and interpretation of a clinical trial (6).


Gynecology_Novak

Gynecology_Novak. Observational Studies In cases where the exposure and outcome are not amenable to an experimental design, because the exposure is known or suspected to have harmful effects, observational studies may be used to assess association. Observational studies, including cohort, case-control, and cross-sectional studies, are analytic studies that take advantage of “natural experiments” in which exposure is not assigned by the investigator; rather, the individuals are assessed by the investigator for a potential exposure of interest (present or absent) and outcomes (present or absent). The timing of the evaluation of the exposure and outcome defines the study type. No disease Disease Prospective 2011 Historical cohort 1988 2028 2011 Exposed group Unexposed group Disease-free population No disease Prospective assessment of the outcome Prospective assessment of the outcome Disease Figure 4.2 Schematic of prospective and retrospective cohort study designs.


Gynecology_Novak

Gynecology_Novak. Figure 4.2 Schematic of prospective and retrospective cohort study designs. Cohort Studies Cohort studies often are referred to as longitudinal studies. Cohort studies involve identifying a group of exposed individuals and unexposed individuals and following both groups over time to compare the rate of disease (or outcome) in the groups. Cohort studies may be prospective, meaning that the exposure is identified before outcome, or retrospective, in which the exposure and outcome have already occurred when the study is initiated. Even in a retrospective cohort study, the study is defined by the fact that the cohorts were identified based on the exposure (not the outcome), and individuals should be free of disease (outcome) at the beginning time point for the cohort study (Fig. 4.2).


Gynecology_Novak

Gynecology_Novak. In a study that includes a survival analysis, the two cohort groups (exposed and nonexposed) begin with a population that is 100% well (or alive) at the beginning of the study. The groups are followed over time to calculate the percentage of the cohort still well (or alive) at different time points during the study and at the end of the study. Although a survival analysis typically describes mortality after disease (i.e., cancer patients who died within 5 years), it can be adapted to other events and outcomes (e.g., the percentage of women who become pregnant while using long-acting contraceptives).


Gynecology_Novak

Gynecology_Novak. Strengths of cohort studies include the ability to obtain both attributable and relative risks because the occurrence of the outcome is being compared in two groups (see the section on Presenting and Understanding the Results of Analytic Studies). However, only associations can be established, not causality. Because randomization is not part of the study design, the investigator must consider that a factor associated with the exposure may lead to the outcome rather than the exposure itself. Misclassifying the exposure or the outcome and confounding variables are potential sources of bias in cohort studies. Given that truly prospective cohort studies can be expensive and take a long time for completion, there should be compelling evidence for the public health importance of the exposure(s) and association(s) being addressed. Issues related to sample size and participant retention in the study protocol are as important in cohort studies as they are in randomized controlled trials.


Gynecology_Novak

Gynecology_Novak. Retrospective assessment of the exposure 2011 1998 Exposed Unexposed Patient population Group with disease Group without disease Exposed Unexposed Figure 4.3 Schematic of case control study design. Case-Control Studies A case-control study starts with the identification of individuals with a disease or outcome of interest and a suitable control population without the disease or outcome of interest. The controls should represent a sample of the population from which the cases arose and who were at risk for the disease or outcome but did not develop it. The relationship between a particular attribute or exposure to the disease is retrospectively studied by comparing how the cases and controls differed in that exposure (Fig. 4.3).


Gynecology_Novak

Gynecology_Novak. Odds Ratio The measure of association for a case-control study is the odds ratio, which is the ratio of exposed cases to unexposed cases, divided by the ratio of exposed to unexposed controls (see the section on Presenting and Understanding the Results of Analytic Studies). If an entire population could be characterized by its exposure and disease status, the exposure odds ratio would be identical to the relative risk obtainable from a cohort study of the same population. Although the relative risk (RR) cannot be calculated directly from a case control study, it can be used as an estimate of the relative risk when the sample of cases and controls are representative of all people with or without the disease and when the disease being studied is uncommon. Attributable risk is not directly obtainable in a case-control study.


Gynecology_Novak

Gynecology_Novak. The advantages of case-control studies are that they are generally lower in cost and easier to conduct than other analytic studies. Case-control studies are most feasible for examining the association between a relatively common exposure and a relatively rare disease. Disadvantages include greater potential for selection bias, recall bias, and misclassification bias. Case-control studies may be especially prone to selection bias and recall bias. Investigators need to understand sampling issues around which cases and controls were selected for their study and how these may have affected exposure rates. Subtle issues, such as interviewer technique, may affect the likelihood that cases may recall or report exposures more readily than controls.


Gynecology_Novak

Gynecology_Novak. Cross-Sectional Studies Cross-sectional studies assess both the exposure and the outcome at the same point in time. Individuals are surveyed to provide a “snapshot” of health events in the population at a particular time. Cross-sectional studies are often called prevalence studies because the disease exists at the time of the study, and the longitudinal follow-up and disease duration are not known. Prevalence is the existing number of cases at a specific point in time. Cross-sectional studies are often done to evaluate a diagnostic test. The value of the test (predictor) is compared with the outcome (disease). The results of these evaluations are often Prevalence of disease is 50% Sensitivity (a/a + c): 95/100 = 95% Specificity (d/b + d): 95/100 = 95% PPV (a/a + b): 95/100 = 95% NPV (d/c + d): 95/100 = 95% Prevalence of disease is 9% Sensitivity: 95/100 = 95% Specificity: 950/1000 = 95% PPV: 95/145 = 65.5% NPV: 950/955 = 99.5%


Gynecology_Novak

Gynecology_Novak. Prevalence of disease is 9% Sensitivity: 95/100 = 95% Specificity: 950/1000 = 95% PPV: 95/145 = 65.5% NPV: 950/955 = 99.5% Figure 4.4 Comparison of sensitivity, specificity and predictive values when the prevalence of the disease varies. presented as sensitivity and specificity. The sensitivity and specificity represent the characteristics of a given diagnostic test and do not vary by population characteristics. In contrast the negative and positive predictive values of a test do vary with the baseline characteristics of a population such as prevalence of a disease (Fig. 4.4). Descriptive studies, case reports and case series, do not include comparison groups.


Gynecology_Novak

Gynecology_Novak. Descriptive studies, case reports and case series, do not include comparison groups. In a case report or case series, the characteristics of individuals who have a particular disease are described. A case report usually describes an unusual clinical scenario or procedure in a single patient, whereas a case series usually includes a larger group of patients with similar exposures or outcomes. Just because members of a case series share a particular characteristic, it cannot be assumed that there is a cause-and-effect relationship. Hypotheses about exposures and disease may be developed from descriptive studies that should then be explored in analytic studies. Because a case series has no comparison group, statistical tests of association between the exposure and outcome cannot be performed. A case series usually does not yield any measure of association other than estimates of the frequency of a particular characteristic among members included in the case series.


Gynecology_Novak

Gynecology_Novak. Presenting and Understanding the Results of Analytic Studies To present the results of clinical trials or observational studies, a variety of rates and measures may be derived, as summarized below. To judge the scientific validity of the results of clinical studies, an investigator needs to consider whether the finding could have occurred simply by chance, by performing appropriate statistical testing, or if there are other possible explanations for the reported association, including bias or confounding. Besides statistical significance and freedom from bias or confounding, there are several additional criteria that can be applied to judge whether the treatment truly did affect disease outcome or whether an exposure truly caused the disease, as outlined below. Rates and Measures The terminology associated with rates and measures include (Fig. 4.5): Incidence (IR)—frequency of newly identified disease or event (outcome).


Gynecology_Novak

Gynecology_Novak. Rates and Measures The terminology associated with rates and measures include (Fig. 4.5): Incidence (IR)—frequency of newly identified disease or event (outcome). Prevalence (PR)—frequency of an existing disease or outcome during a specified period or point in time. Odds Ratios (OR)—ratio of the probability of an exposure in one group (cases) compared with probability of the exposure in another group (controls). Relative Risk (RR)—ratio of risk in the exposed group compared with the risk in the unexposed group. If the RR = 1 (or not significantly different from 1) then the risk in the exposed group is equal to the risk in the nonexposed group. RR >1 may suggest a positive association with the exposed group having greater risk than the nonexposed group, whereas a RR <1 implies a negative association with the exposed group having less risk than the nonexposed group.


Gynecology_Novak

Gynecology_Novak. Absolute Risk Reduction (ARR)—the difference in risk between the unexposed (control) group and the exposed (treatment) group.  Overall Incidence Rate (IR): (a + c) (a + b + c + d)  Odds Ratio (OR): (a/b) (c/d)  Relative Risk (RR): (a/(a + b)) (d/(c + d))  Relative Risk Reductions (RRR): 1-RR x 100%  Absolute Risk Reduction (ARR): (a/(a +b)) – (d/(c + d))  Number Needed to Treat (NNT): 1 ARR Figure 4.5 Calculating rates and measures. Relative Risk Reduction (RRR)—the percentage of reduction in the risk comparing the unexposed (control) group to the exposed (treatment) group. Number Needed to Treat (NNT)—represents the number of people who would need treatment (or the intervention) to prevent one additional outcome (to calculate the NNT, take the inverse of the ARR, i.e., 1 ÷ ARR). Sensitivity—among the people who have the outcome, this is the proportion who have a positive test.


Gynecology_Novak

Gynecology_Novak. Sensitivity—among the people who have the outcome, this is the proportion who have a positive test. Specificity—among the people who do not have the outcome, this is the proportion who have a negative test. Negative Predictive Value (NPV)—among the people who have a negative test, this is the proportion who do not have the outcome. Positive Predictive Value (PPV)—among the people who have a positive test, this is the proportion who have the outcome.


Gynecology_Novak

Gynecology_Novak. Positive Predictive Value (PPV)—among the people who have a positive test, this is the proportion who have the outcome. Statistical Testing Statistical testing is used in clinical research for hypothesis testing in which the investigator is evaluating the study results against the null hypothesis (that there is no difference between the groups). Results from statistical testing allow the investigator to evaluate how likely it is that the study result is caused by chance rather than an intervention or exposure (p value). In the case where a study failed to find a significant difference, it is equally important to describe the likelihood that the study conclusion was wrong and that a difference truly exists. Finally, it is important to provide as precise a measure of the treatment effect or association as possible and convey to the reader the plausible range that the “true” effect resides (or confidence interval).


Gynecology_Novak

Gynecology_Novak. The p value is a reﬂection of the probability of a type I error (alpha). This reﬂects the probability that a difference between study groups could have arisen by chance alone. In other words, it is the probability that there is a difference between therapies, interventions, or observed groups when a true difference does not exist. Historically in the medical literature, a p value of less than or equal to 0.05 was used to determine statistical significance. This reﬂects a probability of 1 in 20 that the null hypothesis was rejected based on the results from the study sample. This p value may be adjusted downward if multiple associations are being tested and the chances of false discovery are high. In genome-wide association studies, in which hundreds of thousands of genetic variants are tested between groups, p values are frequently set at 10−7 (0.0000001).


Gynecology_Novak

Gynecology_Novak. Beta Error and Power Type II (or beta) error reﬂects the probability of failing to reject the null hypothesis when in reality it is incorrect (i.e., there truly was a treatment effect or a difference between the observed groups). In clinical trials it is important for the investigator to address the beta error, even in the design stage of the study. Study planners should calculate the power (or 1–the beta error) that their study would have to detect an association, given assumptions made about the differences expected between treatments, and design the study size accordingly. Be aware that small clinical trials cited as evidence for “no effect of therapy,” may not have an adequate sample size to address the study question; in essence, the study is not powered to detect the difference.


Gynecology_Novak

Gynecology_Novak. Confidence Intervals Confidence intervals (CI) provide the investigator an estimated range in which the true statistical measure (e.g., mean, proportion, and relative risk) is expected to occur. A 95% confidence interval implies that if the study were to be repeated within the same sample population numerous times, the confidence interval estimates would contain the true population parameter 95% of the time. In other words, the probability of observing the true value outside of this range is less than 0.05. When evaluating measures of association, such as odds ratio or relative risk with 95% CI, values that include 1 (no difference) are not considered statistically significant.


Gynecology_Novak

Gynecology_Novak. Meta-analysis One way of improving precision of the effect measure and narrowing the confidence interval is to perform a meta-analysis in which treatment effects from several clinical trials are aggregated to provide a summary measure. Meta-analysis is a favorite tool of the Cochrane database, with which clinicians should be familiar (8). However, there are important considerations in interpreting the meta-analysis, including whether studies were similar enough in their design to be aggregated. Guides for systematic reviews and meta-analysis that involve randomized controlled trials (i.e., the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] statement) and observational studies (i.e., the Meta-analysis Of Observational Studies in Epidemiology [MOOSE] guidelines) are excellent resources for both the investigator and the reviewer (9,10).


Gynecology_Novak

Gynecology_Novak. Bias Bias is a systematic error in the design, conduct, or analysis of a study that can result in invalid conclusions. It is important for an investigator to anticipate the types of bias that might occur in a study and correct them during the design of the study, because it may be difficult or impossible to correct for them in the analysis. Information bias occurs when participants are classified incorrectly with respect to exposure or disease. This may occur if records are incomplete or if the criteria for exposure or outcome were poorly defined, leading to misclassification. Recall bias is a specific type of information bias that may occur if cases are more likely than controls to remember or to reveal past exposures. In addition to establishing well-defined study criteria and accessing complete records, information bias may be reduced by blinding interviewers to a participant’s study group.


Gynecology_Novak

Gynecology_Novak. Selection bias may occur when choosing cases or controls in a case-control study and when choosing exposed or unexposed subjects in a cohort study. A systematic error in selecting participants may inﬂuence the outcome by distorting the measure of association between the exposure and the outcome. Including an adequately large study sample and obtaining information about nonparticipants may reduce bias or provide information to evaluate potential selection bias. Confounding A confounder is a known risk factor for the disease and is associated with the exposure. The confounder may account for the apparent effect of the exposure on the disease or mask a true association. Confounders have unequal distributions between the study groups.


Gynecology_Novak

Gynecology_Novak. Age, race, and socioeconomic status are potential confounders in many studies. Results may be adjusted for these variables by using statistical techniques such as stratification or multivariable analysis. Adjusting for confounding variables aids in understanding the association between the outcome and exposure if the confounding variable were constant. Multivariable analysis is a statistical technique commonly used in epidemiologic studies that simultaneously controls a number of confounding variables. The results from an adjusted analysis include the adjusted odds ratio or relative risk that reﬂects an association between the exposure and the outcome and accounts for the specific known confounders that were included in the analysis.


Gynecology_Novak

Gynecology_Novak. The criteria needed to establish a causal relationship between two factors, especially exposure and disease, are defined (11). Although there are nine separate criteria for judging whether an association is likely to be causal, several of these criteria are most relevant for clinical studies. Biologic gradient or dose response refers to a relationship between exposure and outcome such that a change in the duration, amount, or intensity of the exposure is associated with a corresponding increase or decrease in disease risk. Plausibility refers to knowledge of the pathologic process of the disease or biologic effects of the exposure that would reasonably support an association. Plausibility overlaps with another concept, coherence, which also refers to compatibility with the known biology of the disease. Experiment refers to the evidence that the disease or outcome can be prevented or improved by an experiment that eliminates, reduces, or otherwise counters the exposure.


Gynecology_Novak

Gynecology_Novak. Experiment refers to the evidence that the disease or outcome can be prevented or improved by an experiment that eliminates, reduces, or otherwise counters the exposure. Consistency refers to whether the association was repeatedly observed by different investigators, in different locations and circumstances. Temporality refers to the concept that cause must precede effect. For example, is it possible in a case-control study that symptoms of preclinical disease could lead to the exposure? Investigators must demonstrate that the exposure was present before the disease developed.


Gynecology_Novak

Gynecology_Novak. Strength refers to the strength of association. The further the deviation of the relative risk or odds ratio from 1, the stronger the association and the easier it is to accept that the study results are real. For example, studies have shown that the possession of a BRCA mutation may increase the lifetime risk for ovarian or breast cancer some 30-fold. Although strength is a very important criterion, large-scale genetic studies suggest that other factors are equally important. For example, multiple studies reported several variants at the 8q24 chromosomal region associated with prostate and other cancers (12). Even though possession of one allele may change risk by only about 15% (i.e., OR = 1.15), the consistency and high statistical significance suggest the association cannot be caused by chance and this is considered a true association.


Gynecology_Novak

Gynecology_Novak. Reviewing the medical literature is part of the ongoing education for those who provide clinical care. Incorporating research findings into clinical care is enhanced by understanding different study designs, their strengths and weaknesses, and the measures of association they are able to provide. Evaluating whether there is enough evidence available to support changing a specific medication, procedure, or protocol used to care for patients is the cornerstone to improving clinical practice. In a field that is rapidly progressing, understanding clinical research helps physicians provide optimal care for the women they treat everyday. Eric R. Sokol Rene Genadry Jean R. Anderson Although the basic facts of anatomy do not change, our understanding of specific anatomic relationships and the development of new clinical and surgical correlations continue to evolve.


Gynecology_Novak

Gynecology_Novak. Although the basic facts of anatomy do not change, our understanding of specific anatomic relationships and the development of new clinical and surgical correlations continue to evolve. There is significant variation in the branching pattern of pelvic blood vessels between individuals, and patterns of blood ﬂow may be asymmetric from side to side in the same individual. The pelvic surgeon should be prepared for deviations from “textbook” vascular patterns. An understanding of the development of pelvic ﬂoor disorders and their safe and effective management requires a comprehensive knowledge of the interrelationships between the bony pelvis and its ligaments, pelvic muscles and fasciae, nerves and blood vessels, and pelvic viscera. Approximately 10% of infants are born with some abnormality of the genitourinary system, and anomalies in one system are often mirrored by anomalies in another system that provide special implications in pelvic surgery.


Gynecology_Novak

Gynecology_Novak. About 75% of all iatrogenic injuries to the ureter result from gynecologic procedures, most commonly abdominal hysterectomy; risk is increased with distortions of pelvic anatomy, including adnexal masses, endometriosis, other pelvic adhesive disease, or fibroids. An understanding of the anatomy of the female pelvis is fundamental to the knowledge base of a practicing gynecologist. Although the basic facts of anatomy and their relevance to gynecologic practice do not change with time, our understanding of specific anatomic relationships and the development of new clinical and surgical correlations continue to evolve.


Gynecology_Novak

Gynecology_Novak. The anatomy of the fundamental supporting structures of the pelvis, including the genital, urinary, and gastrointestinal viscera, are presented in this chapter. Because significant variation has developed in the names of many common anatomic structures, the terms used here reﬂect current nomenclature according to the Nomina Anatomica; other commonly accepted terms are included in parentheses (1). Bony Pelvis The skeleton of the pelvis is formed by the sacrum and coccyx and the paired hipbones (coxal, innominate), which fuse anteriorly to form the symphysis pubis. Figure 5.1 illustrates the bony pelvis as well as its ligaments and foramina. Sacrum and Coccyx The sacrum and coccyx are an extension of the vertebral column resulting from the five fused sacral vertebrae and the four fused coccygeal vertebrae. They are joined by a symphyseal articulation (sacrococcygeal joint), which allows some movement. The essential features of the sacrum and coccyx are as follows: 1.


Gynecology_Novak

Gynecology_Novak. The essential features of the sacrum and coccyx are as follows: 1. Sacral promontory—the most prominent and anterior projection of the sacrum, this is an important landmark for insertion of a laparoscope and for sacrocolpopexy. It is located just below the level of bifurcation of the common iliac arteries. 2. Four paired anterior and posterior sacral foramina—exit sites for the anterior and posterior rami of the corresponding sacral nerves; the lateral sacral vessels also traverse the anterior foramina. 3. Sacral hiatus—results from incomplete fusion of the posterior lamina of the fifth sacral vertebra, offering access to the sacral canal, which is clinically important for caudal anesthesia. Laterally, the alae (“wings”) of the sacrum offer auricular surfaces that articulate with the hipbones to form synovial sacroiliac joints.


Gynecology_Novak

Gynecology_Novak. Laterally, the alae (“wings”) of the sacrum offer auricular surfaces that articulate with the hipbones to form synovial sacroiliac joints. Os Coxae The paired os coxae, or hipbones, have three components: the ilium, the ischium, and the pubis. These components meet to form the acetabulum, a cup-shaped cavity that accommodates the femoral head. Figure 5.1 The female pelvis. The pelvic bones (the innominate bone, sacrum, and coccyx) and their joints, ligaments, and foramina. 1. Iliac crest—provides attachments to the iliac fascia, abdominal muscles, and fascia lata. 2. Anterior superior and inferior spine—superior spine provides the point of fixation of the inguinal ligament and is clinically important as a lateral landmark for laparoscopic entry. 3. Posterior superior and inferior spine—superior spine is the point of attachment for the sacrotuberous ligament and the posterior sacral iliac ligament. 4.


Gynecology_Novak

Gynecology_Novak. 3. Posterior superior and inferior spine—superior spine is the point of attachment for the sacrotuberous ligament and the posterior sacral iliac ligament. 4. Arcuate line—marks the pelvic brim and lies between the first two segments of the sacrum. 5. Iliopectineal eminence (linea terminalis)—the junction line of the ilium and the pubis. 6. Iliac fossa—the smooth anterior concavity of the ilium, covered by the iliacus muscle. 1. Ischial spine—delineates the greater and lesser sciatic notch above and below it. It is the point of fixation for the sacrospinous ligament and the arcus tendineus fascia pelvis (white line); the ischial spine represents an important landmark in the performance of pudendal nerve block and sacrospinous ligament vaginal suspension; vaginal palpation during labor allows detection of progressive fetal descent. 2.


Gynecology_Novak

Gynecology_Novak. 2. Ischial ramus—joins the pubic rami to encircle the obturator foramen; provides the attachment for the inferior fascia of the urogenital diaphragm and the perineal musculofascial attachments. 3. Ischial tuberosity—the rounded bony prominence upon which the body rests in the sitting position; a clinical landmark for the passage of the inferior arm of anterior vaginal mesh kit systems. 1. Body—formed by the midline fusion of the superior and inferior pubic rami. 2. Symphysis pubis—a fibrocartilaginous symphyseal joint where the bodies of the pubis meet in the midline, allows for some resilience and ﬂexibility, which is critical during parturition. 3. Superior and inferior pubic rami—join the ischial rami to encircle the obturator foramen; provide the origin for the muscles of the thigh and leg; provide the attachment for the inferior layer of the urogenital diaphragm; the inferior rami is a clinical landmark for transobturator incontinence sling passage. 4.


Gynecology_Novak

Gynecology_Novak. 4. Pubic tubercle—a lateral projection from the superior pubic ramus, to which the inguinal ligament, rectus abdominis, and pyramidalis attach.


Gynecology_Novak

Gynecology_Novak. Clinical Considerations Studies using magnetic resonance imaging (MRI) or computed tomography (CT) pelvimetry found an association between the architecture of the bony pelvis, specifically a wider transverse inlet (distance between the most superior aspects of the iliopectineal line) and a shorter obstetric conjugate (shortest distance between the sacral promontory and the pubic symphysis), and the occurrence of pelvic ﬂoor disorders (2,3). A loss of lumbar lordosis and a pelvic inlet that is less vertically oriented is more common in women who develop genital prolapse than in those who do not (4,5). A less vertical orientation of the pelvic inlet is thought to result in an alteration of the intra-abdominal forces that are normally directed anteriorly to the pubic symphysis such that a greater proportion is directed toward the pelvic viscera and their connective tissue and muscular supports. It is theorized that women with a wide pelvic inlet are more likely to develop pelvic organ


Gynecology_Novak

Gynecology_Novak. greater proportion is directed toward the pelvic viscera and their connective tissue and muscular supports. It is theorized that women with a wide pelvic inlet are more likely to develop pelvic organ prolapse (2,3). It is speculated that women with these characteristics may be more likely to suffer neuromuscular and connective tissue injuries during labor and delivery, predisposing them to the development of pelvic neuropathy, pelvic organ prolapse, or both. One MRI study, in which only white women were enrolled to remove race as a potential confounder, found that bony pelvis dimensions were similar at the level of the muscular pelvic ﬂoor with and without pelvic organ prolapse (6).


Gynecology_Novak

Gynecology_Novak. Pelvic Bone Articulations The pelvic bones are joined by four articulations (two pairs): 1. Two cartilaginous symphyseal joints—the sacrococcygeal joint and the symphysis pubis—these joints are surrounded by strong ligaments anteriorly and posteriorly, which are responsive to the effect of relaxin and facilitate parturition. 2. Two synovial joints—the sacroiliac joints—these joints are stabilized by the sacroiliac ligaments, the iliolumbar ligament, the lateral lumbosacral ligament, the sacrotuberous ligament, and the sacrospinous ligament.


Gynecology_Novak

Gynecology_Novak. The pelvis is divided into the greater and lesser pelvis by an oblique plane passing through the sacral promontory, the linea terminalis (arcuate line of the ilium), the pectineal line of the pubis, the pubic crest, and the upper margin of the symphysis pubis. This plane lies at the level of the superior pelvic aperture (pelvic inlet) or pelvic brim. The inferior pelvic aperture or pelvic outlet is irregularly bound by the tip of the coccyx, the symphysis pubis, and the ischial tuberosities. The dimensions of the superior and inferior pelvic apertures have important obstetric implications. Ligaments Four ligaments—inguinal, Cooper’s, sacrospinous, and sacrotuberous—of the bony pelvis are of special importance to the gynecologic surgeon. The inguinal ligament is important surgically in the repair of inguinal hernia. The inguinal ligament: 1. Is formed by the lower border of the aponeurosis of the external oblique muscle folded back upon itself. 2.


Gynecology_Novak

Gynecology_Novak. Is formed by the lower border of the aponeurosis of the external oblique muscle folded back upon itself. 2. Is fused laterally to the iliacus fascia and inferiorly to the fascia lata. 3. Flattens medially into the lacunar ligament, which forms the medial border of the femoral ring. Cooper’s ligament is used frequently in bladder suspension procedures. Cooper’s ligament: 1. Is a strong ridge of fibrous tissue extending along the pectineal line—also known as the pectineal ligament. 2. Merges laterally with the iliopectineal ligament and medially with the lacunar ligament. The sacrospinous ligament is often used for vaginal suspension. This ligament offers the advantage of a vaginal surgical route. The sacrospinous ligament: 1. Extends from the ischial spine to the lateral aspect of the sacrum. 2. Is separated from the rectovaginal space by the rectal pillars. 3. Lies anterior to the pudendal nerve and the internal pudendal vessels at its attachment to the ischial spine.


Gynecology_Novak

Gynecology_Novak. 2. Is separated from the rectovaginal space by the rectal pillars. 3. Lies anterior to the pudendal nerve and the internal pudendal vessels at its attachment to the ischial spine. The inferior gluteal artery, with extensive collateral circulation, is found between the sacrospinous and sacrotuberous ligaments and may be injured during sacrospinous suspension (Fig. 5.2) (7). Injury to the inferior gluteal artery, and to the pudendal nerve and internal pudendal vessels, during sacrospinous ligament suspension may be minimized by careful and controlled retraction and suture placement at least two fingerbreadths medial to the ischial spine. The sacrotuberous ligament is sometimes used as a point of fixation for vaginal vault suspension. The sacrotuberous ligament: 1. Extends from the ischial tuberosity to the lateral aspect of the sacrum. 2. Merges medially with the sacrospinous ligament. 3. Lies posterior to the pudendal nerve and the internal pudendal vessels.


Gynecology_Novak

Gynecology_Novak. 2. Merges medially with the sacrospinous ligament. 3. Lies posterior to the pudendal nerve and the internal pudendal vessels. Figure 5.2 Tone drawing of left hemipelvis with sacrospinous ligament reﬂected. a., artery; Inf., inferior; lig., ligament; n., nerve; Sacrosp., sacrospinous; Sacrotub., sacrotuberous. (Redrawn from Thompson JR, Gibbs JS, Genadry R, et al. Anatomy of pelvic arteries adjacent to the sacrospinous ligament: importance of the coccygeal branch of the inferior gluteal artery. Obstet Gynecol 1999;94:973–977, with permission.) Figure 5.3 The pelvic diaphragm. A: A view into the pelvic ﬂoor that illustrates the muscles of the pelvic diaphragm and their attachments to the bony pelvis. B: A view from outside the pelvic diaphragm illustrating the divisions of the levator ani muscles (superficial plane removed on the right). (continued )


Gynecology_Novak

Gynecology_Novak. Figure 5.3 (Continued ) C: A lateral, sagittal view of the pelvic diaphragm and superior fascia of the urogenital diaphragm. The muscles include the deep transverse perineal and sphincter urethrae. The pelvic diaphragm is a funnel-shaped fibromuscular partition that forms the primary supporting structure for the pelvic contents (Fig. 5.4). It is composed of the levator ani (pubococcygeus, puborectalis, iliococcygeus) and the coccygeus muscles, along with their superior and inferior fasciae (Table 5.1). It forms the ceiling of the ischiorectal fossa.


Gynecology_Novak

Gynecology_Novak. The levator ani muscles are composed of the pubococcygeus (including the pubovaginalis and pubourethralis, puborectalis, and the iliococcygeus). The levator ani is a broad, curved sheet of muscle stretching anteriorly from the pubis and posteriorly from the coccyx and from one side of the pelvis to the other. It is perforated by the urethra, vagina, and anal canal. Its origin is from the tendinous arch extending from the body of the pubis to the ischial spine. This tendineus arch, called the arcus tendineus levator ani, is formed by a thickening of the obturator fascia and serves as a lateral landmark and point of attachment for some vaginal suspension procedures. The levator ani is inserted into the central tendon of the perineum, the wall of the anal canal, the anococcygeal ligament, the coccyx, and the vaginal wall.


Gynecology_Novak

Gynecology_Novak. The levator ani assists the anterior abdominal wall muscles in containing the abdominal and pelvic contents. It supports the vagina, facilitates defecation, and aids in maintaining fecal continence. During parturition, the levator ani supports the fetal head while the cervix dilates. The anterior portion of the levator ani complex serves to close the urogenital hiatus and pull the urethra, vagina, perineum, and anorectum toward the pubic bone, whereas the horizontally oriented posterior portion (levator plate) serves as a supportive diaphragm or “backstop” behind the pelvic viscera. Loss of normal levator ani tone, through denervation or direct muscle trauma, results in laxity of the urogenital hiatus, loss of the horizontal orientation of the levator plate, and a more bowl-like configuration. These changes can be bilateral or asymmetric (8). Such configurations are seen more often in women with pelvic organ prolapse than in those with normal pelvic organ support (9).


Gynecology_Novak

Table 5.1 Muscles of the Pelvic Floor

Gynecology_Novak. Table 5.1 Muscles of the Pelvic Floor


Gynecology_Novak

Gynecology_Novak. Traditional teaching is that the levator ani muscles are innervated by the pudendal nerve on the perineal surface and direct branches of the sacral nerves on the pelvic surface. Evidence indicates that the levator ani muscles are innervated solely by a nerve traveling on the superior (intrapelvic) surface of the muscles without the contribution of the pudendal nerve (10–15). This nerve, referred to as the levator ani nerve, originates from S3, S4, and/or S5 and innervates both the coccygeus and the levator ani muscle complex (10). After exiting the sacral foramina, it travels 2 to 3 cm medial to the ischial spine and arcus tendineus levator ani across the coccygeus, iliococcygeus, pubococcygeus, and puborectalis. Occasionally, a separate nerve comes directly from S5 to innervate the puborectalis muscle independently. Given its location, the levator ani nerve is susceptible to injury through parturition and pelvic surgery, such as during sacrospinous or iliococcygeus vaginal vault


Gynecology_Novak

Gynecology_Novak. muscle independently. Given its location, the levator ani nerve is susceptible to injury through parturition and pelvic surgery, such as during sacrospinous or iliococcygeus vaginal vault suspensions.


Gynecology_Novak

Gynecology_Novak. Figure 5.4 The ligaments and fascial support of the pelvic viscera. The muscles of the urogenital diaphragm anteriorly reinforce the pelvic diaphragm and are intimately related to the vagina and the urethra. They are enclosed between the inferior and superior fascia of the urogenital diaphragm. The muscles include the deep transverse perineal and sphincter urethrae (Table 5.1). Blood Vessels The pelvic blood vessels supply genital structures as well as the following: Urinary and gastrointestinal tracts Muscles of the abdominal wall, pelvic ﬂoor and perineum, buttocks, and upper thighs Fasciae, other connective tissue, and bones Skin and other superficial structures Classically, vessels supplying organs are known as visceral vessels and those supplying supporting structures are called parietal vessels.


Gynecology_Novak

Gynecology_Novak. Classically, vessels supplying organs are known as visceral vessels and those supplying supporting structures are called parietal vessels. Major Blood Vessels The course of the major vessels supplying the pelvis is illustrated in Figure 5.5; their origin, course, branches, and venous drainage are presented in Table 5.2. In general, the venous system draining the pelvis closely follows the arterial supply and is named accordingly. Not infrequently, a vein draining a particular area may form a plexus with multiple channels. Venous systems, which are paired, mirror each other in their drainage patterns, with the notable exception of the ovarian veins. Unusual features of venous drainage are also listed in Table 5.2. Figure 5.5 The blood supply to the pelvis. A: The sagittal view of the pelvis without the viscera. B: The blood supply to one pelvic viscera. Table 5.2 The Major Blood Vessels of the Pelvis


Gynecology_Novak

Gynecology_Novak. Figure 5.5 The blood supply to the pelvis. A: The sagittal view of the pelvis without the viscera. B: The blood supply to one pelvic viscera. Table 5.2 The Major Blood Vessels of the Pelvis Ovarian Arises from ventral Crosses over common iliac vessels; in To ovaries, fallopian tubes, broad ligament; often Right side drains into the surface of aorta just proximity to ureter over much of its small branches to ureter inferior vena cava; left below the origin of the course, crosses over ureter while drains into the left renal vessels superficial to the psoas muscle and renal vein runs just lateral to the ureter when entering the pelvis as part of the infundibulopelvic ligament


Gynecology_Novak

Gynecology_Novak. Inferior mesenteric Unpaired left-sided IMA and its branches pass over the left 1. Left colic—originates above pelvic brim; Inferior mesenteric vein artery (IMA) retroperitoneal artery psoas muscle and common iliac supplies left transverse colon, splenicﬂexure, empties into the arising from the aorta vessels; IMA courses anterior to the descending colon splenic vein 2–5 cm proximal to its ureter and ovarian vessels above the 2. Sigmoid—several branches; supply sigmoid 3. Superior rectal (hemorrhoidal)—divides into two terminal branches to supply rectum Common iliac Terminal division of the Oblique and lateral course, about 1. External iliac Lie posterior and slightly artery aorta at fourth lumbar 5 cm in length medial to arteries; drain 2. Internal iliac


Gynecology_Novak

Gynecology_Novak. External iliac Lateral bifurcation of Along the medial border of the psoas femoral artery common iliac, begins muscle and lateral pelvic side wall; opposite the becomes femoral artery after passing lumbosacral joint under the inguinal ligament to supply lower extremity 1. Superficial epigastric—supplies skin and subcutaneous tissue of lower anterior abdominal wall 2. External pudendal—supplies skin and subcutaneous tissue of mons pubis and anterior vulva 3. Superficial circumﬂex iliac—suppliesskin/subcutaneous tissues of theﬂank 4. Inferior epigastric—supplies musculofascial layer of lower anterior abdominal wall 5. Deep circumﬂex iliac—suppliesmusculofascial layer of lower abdominal wall Lie posterior and then medial to the artery as it enters the anterior thigh; drain into common iliac veins


Gynecology_Novak

Gynecology_Novak. Lie posterior and then medial to the artery as it enters the anterior thigh; drain into common iliac veins Internal iliac Medial bifurcation of Descends sharply into the pelvis; Posterior division Deep to arteries, from (hypogastric) common iliac artery, divides into an anterior and 1. Iliolumbar—anastomoses with lumbar and complex plexus; drain artery begins opposite the posterior division 3–4 cm after deep circumﬂex iliac arteries; helps supply into common iliac lumbosacral joint; is origin lower abdominal wall, iliac fossa veins major blood supply to 2. Lateral sacral—supplies contents of sacral the pelvis canal, piriformis muscle 3. Superior gluteal—supplies gluteal muscles Anterior division: 1. Obturator—supplies iliac fossa, posterior pubis, obturator internus muscle 2. 3.


Gynecology_Novak

Gynecology_Novak. Anterior division: 1. Obturator—supplies iliac fossa, posterior pubis, obturator internus muscle 2. 3. Umbilical—remnant of fetal umbilical artery; after giving off branches, as the medial umbilical ligament 4. Superior, middle, inferior vesical—supply bladder and one or more branches to the ureter 5. Middle rectal (hemorrhoidal)—suppliesrectum, branches to midvagina 6. Uterine—supplies uterine corpus and cervix, with branches to upper vagina, tube, round ligament, and ovary 7. 8. Inferior gluteal—supplies gluteal muscles, muscles of posterior thigh Internal pudendal Internal iliac artery; artery provides the major blood supply to the perineum


Gynecology_Novak

Gynecology_Novak. 8. Inferior gluteal—supplies gluteal muscles, muscles of posterior thigh Internal pudendal Internal iliac artery; artery provides the major blood supply to the perineum Leaves the pelvis through the greater sciatic foramen, courses around the ischial spine, and enters the ischiorectal fossa through the lesser sciatic foramen. In its path to the perineum, lies with the pudendal nerve within Alcock’s canal, a fascial tunnel over the obturator internus muscle 1. Inferior rectal (hemorrhoids)—supplies anal Drain into internal iliac canal, external anal sphincter, perianal skin, veins with branches to levator ani 2. Perineal—supplies perineal skin, muscles of superficial perineal compartment (bulbocavernosus, ischiocavernosus, superficial transverse perineal) 3. Clitoral—supplies clitoris, vestibular bulb, Bartholin gland, and urethra


Gynecology_Novak

Gynecology_Novak. Middle sacral Midline unpaired vessel Courses over lower lumbar vertebrae, Supplies bony and muscular structures of Paired middle sacral artery arising from posterior sacrum, and coccyx posterior pelvic wall veins usually drain into terminal aorta left common iliac vein Lumbar arteries Segmental branches Pass around the side of the 4 superior Supplies abdominal wall musculature Veins into inferior vena arising at each lumbar lumbar vertebrae, divide into (external/internal oblique, transversus cava level from posterior anterior and posterior branches abdominis) aorta General Principles “Control blood supply” and “maintain meticulous hemostasis” are two of the most common exhortations to young surgeons. In developing familiarity with the pattern of blood ﬂow in the pelvis, several unique characteristics of this vasculature should be understood because of their potential implications to surgical practice: 1.


Gynecology_Novak

Gynecology_Novak. The pelvic vessels play an important role in pelvic support. They provide condensations of endopelvic fascia that act to reinforce the normal position of pelvic organs (16). 2.


Gynecology_Novak

Gynecology_Novak. There is significant anatomic variation between individuals in the branching pattern of the internal iliac vessels. There is no constant order in which branches divide from the parent vessel; some branches may arise as common trunks or may spring from other branches rather than from the internal iliac. Occasionally, a branch may arise from another vessel entirely (e.g., the obturator artery may arise from the external iliac or inferior epigastric artery). This variation may be found in the branches of other major vessels; the ovarian arteries are reported to arise from the renal arteries or as a common trunk from the front of the aorta on occasion. The inferior gluteal artery may originate from the posterior or the anterior branch of the internal iliac (hypogastric) artery. Patterns of blood ﬂow may be asymmetric from side to side, and structures supplied by anastomoses of different vessels may show variation from person to person in the proportion of vascular support provided by the


Gynecology_Novak

Gynecology_Novak. ﬂow may be asymmetric from side to side, and structures supplied by anastomoses of different vessels may show variation from person to person in the proportion of vascular support provided by the vessels involved (16). The pelvic surgeon must be prepared for deviations from “textbook” vascular patterns.


Gynecology_Novak

Gynecology_Novak. 3. The pelvic vasculature is a high-volume, high-ﬂow system with enormous expansive capabilities throughout reproductive life. Blood ﬂow through the uterine arteries increases to about 500 mL per min in late pregnancy. In nonpregnant women, certain conditions, such as uterine fibroids or malignant neoplasms, may be associated with neovascularization and hypertrophy of existing vessels and a corresponding increase in pelvic blood ﬂow. Understanding the volume and ﬂow characteristics of the pelvic vasculature in different clinical situations will enable the surgeon to anticipate problems and take appropriate preoperative and intraoperative measures (including blood and blood product availability) to prevent or manage hemorrhage. 4.


Gynecology_Novak

Gynecology_Novak. The pelvic vasculature is supplied with an extensive network of collateral connections that provides a rich anastomotic communication between different major vessel systems (Fig. 5.6). This degree of redundancy is important to ensure adequate supply of oxygen and nutrients in the event of major trauma or other vascular compromise. Hypogastric artery ligation continues to be used as a strategy for management of massive pelvic hemorrhage when other measures have failed. Bilateral hypogastric artery ligation, particularly when combined with ovarian artery ligation, dramatically reduces pulse pressure in the pelvis, converting ﬂow characteristics from that of an arterial system to a venous system and allowing use of collateral channels of circulation to continue blood supply to pelvic structures. The significance of collateral blood ﬂow is demonstrated by reports of successful pregnancies occurring after bilateral ligation of both hypogastric and ovarian arteries (17). Table 5.3 lists the


Gynecology_Novak

Gynecology_Novak. The significance of collateral blood ﬂow is demonstrated by reports of successful pregnancies occurring after bilateral ligation of both hypogastric and ovarian arteries (17). Table 5.3 lists the collateral channels of circulation in the pelvis.


Gynecology_Novak

Gynecology_Novak. To avoid injury to vascular structures and resultant hemorrhage while inserting a trocar into the anterior abdominal wall during laparoscopy, the surgeon should keep in mind certain anatomic relationships. The inferior epigastric artery is a branch of the external iliac artery, arising from the parent vessel at the medial border of the inguinal ligament and coursing cephalad lateral to and posterior to the rectus sheath at the level of the arcuate line. It lies about 1.5 cm lateral to the medial umbilical fold, which marks the site of the obliterated umbilical artery. During laparoscopy the inferior epigastric artery almost always can be visualized between the obliterated umbilical artery medially and the insertion of the round ligament through the inguinal canal laterally. This artery can be traced visually cephalad, allowing for safe insertion of lateral port site. The aortic bifurcation occurs at the level of L4 to L5, just above the sacral promontory. Palpation of the sacral


Gynecology_Novak

Gynecology_Novak. can be traced visually cephalad, allowing for safe insertion of lateral port site. The aortic bifurcation occurs at the level of L4 to L5, just above the sacral promontory. Palpation of the sacral promontory to guide trocar insertion allows the surgeon to avoid the major vascular structures in this area (see Fig. 23.4 in Chapter 23). The left common iliac vein lies medial to the artery and is at risk of injury during umbilical laparoscopic trocar insertion and during dissection for sacrocolpopexy.


Gynecology_Novak

Gynecology_Novak. Figure 5.6 The collateral blood vessels of the pelvis. (Modified from Kamina P. Anatomie gyn´ etricale. Paris, France: Maloine Sa ´ ecologique et obst´ Editeur, 1984:125, with permission.) Lymphatics The pelvic lymph nodes are generally arranged in groups or chains and follow the course of the larger pelvic vessels, for which they are usually named. Smaller nodes that lie close to the visceral structures are usually named for those organs. Lymph nodes in the pelvis receive afferent lymphatic vessels from pelvic and perineal visceral and parietal structures and send efferent lymphatics to more proximal nodal groups. The number of lymph nodes and their exact location is variable; however, certain nodes tend to be relatively constant: 1. Obturator node in the obturator foramen, close to the obturator vessels and nerve 2. Nodes at the junction of the internal and external iliac veins Table 5.3 Collateral Arterial Circulation of the Pelvis 3.


Gynecology_Novak

Gynecology_Novak. Nodes at the junction of the internal and external iliac veins Table 5.3 Collateral Arterial Circulation of the Pelvis 3. Ureteral node in the broad ligament near the cervix, where the uterine artery crosses over the ureter 4. The Cloquet or Rosenm¨uller node—the highest of the deep inguinal nodes that lies within the opening of the femoral canal Figure 5.7 illustrates the pelvic lymphatic system. Table 5.4 outlines the major lymphatic chains of relevance to the pelvis and their primary afferent connections from major pelvic and perineal structures. There are extensive interconnections between lymph vessels and nodes; usually more than one lymphatic pathway is available for drainage of each pelvic site. Bilateral and crossed extension of lymphatic ﬂow may occur, and entire groups of nodes may be bypassed to reach more proximal chains.


Gynecology_Novak

Gynecology_Novak. The natural history of most genital tract malignancies directly reﬂects the lymphatic drainage of those structures, although the various interconnections, different lymphatic paths, and individual variability make the spread of malignancy somewhat unpredictable. Regional lymph node metastasis is one of the most important factors in formulation of treatment plans for gynecologic malignancies and prediction of eventual outcome. Nerves The pelvis is innervated by both the autonomic and somatic nervous systems. The autonomic nerves include both sympathetic (adrenergic) and parasympathetic (cholinergic) fibers and provide the primary innervation for genital, urinary, and gastrointestinal visceral structures and blood vessels.


Gynecology_Novak

Gynecology_Novak. Somatic Innervation The lumbosacral plexus and its branches provide motor and sensory somatic innervation to the lower abdominal wall, the pelvic and urogenital diaphragms, the perineum, and the hip and lower extremity (Fig. 5.8). The nerves originating from the muscles, the lumbosacral trunk, the anterior divisions of the upper four sacral nerves (sacral plexus), and the anterior division of the coccygeal nerve and fibers from the fourth and fifth sacral nerves (coccygeal plexus) are found on the anterior surface of the piriformis muscle and lateral to the coccyx, respectively, deep in the posterior pelvis. In Table 5.5 each major branch is listed by spinal segment and structures innervated. In addition to these branches, the lumbosacral plexus includes nerves that innervate


Gynecology_Novak

Gynecology_Novak. Figure 5.7 The lymphatic drainage of the female pelvis. The vulva and lower vagina drain to the superficial and deep inguinal nodes, sometimes directly to the iliac nodes (along the dorsal vein of the clitoris) and to the other side. The cervix and upper vagina drain laterally to the parametrial, obturator, and external iliac nodes and posteriorly along the uterosacral ligaments to the sacral nodes. Drainage from these primary lymph node groups is upward along the infundibulopelvic ligament, similar to drainage of the ovary and fallopian tubes to the para-aortic nodes. The lower uterine body drains in the same manner as the cervix. Rarely, drainage occurs along the round ligament to the inguinal nodes. muscles of the lateral pelvic wall (obturator internus, piriformis), posterior hip muscles, and the pelvic diaphragm. A visceral component, the pelvic splanchnic nerve, is included.


Gynecology_Novak

Gynecology_Novak. muscles of the lateral pelvic wall (obturator internus, piriformis), posterior hip muscles, and the pelvic diaphragm. A visceral component, the pelvic splanchnic nerve, is included. Nerves supplying the cutaneous aspects of the anterior, medial, and lateral lower extremities, and the deep muscles of the anterior thigh, primarily leave the pelvis by passing beneath the inguinal ligament. Nerves supporting the posterior cutaneous and deep structures of the hip, thigh, and leg lie deep in the pelvis and should not be vulnerable to injury during pelvic surgery. The obturator nerve travels along the lateral pelvic wall to pass through the obturator foramen into the upper thigh, and it may be encountered in more radical dissections involving the lateral pelvic wall, in paravaginal repairs, or in trocar-based incontinence and prolapse procedures.


Gynecology_Novak

Gynecology_Novak. The pudendal nerve innervates the striated urethral and anal sphincters and the deep and superficial perineal muscles and provides sensory innervation to the external genitalia. This nerve originates from S2–S4, crosses over the piriformis to travel with the internal pudendal vessels into the ischiorectal fossa through the lesser sciatic foramen, and travels through the pudendal canal (Alcock’s canal) on the medial aspect of the obturator internus muscles, where Table 5.4 Primary Lymph Node Groups Providing Drainage to Genital Structures Inguinal Vulva, lower vagina; (rare: uterus, tube, ovary) it divides into its three terminal branches to provide the primary innervation to the perineum. Other nerves contribute to the cutaneous innervation of the perineum: 1. The anterior labial nerve branches of the ilioinguinal nerve—these nerves emerge from within the inguinal canal and through the superficial inguinal ring to the mons and upper labia majora.


Gynecology_Novak

Gynecology_Novak. Figure 5.8 The sacral plexus. (Modified from Kamina P. Anatomie gyn´ et obst´ Editeur, 1984:90, with permission.) etricale. Paris, France: Maloine Sa ´ Table 5.5 Lumbosacral Plexus 2. The genital branch of the genitofemoral nerve—this branch enters the inguinal canal with the round ligament and passes through the superficial inguinal ring to the anterior vulva. 3. The perineal branches of the posterior femoral cutaneous nerve—after leaving the pelvis through the greater sciatic foramen, these branches run in front of the ischial tuberosity to the lateral perineum and labia majora. 4. Perforating cutaneous branches of the second and third sacral nerves—these branches perforate the sacrotuberous ligament to supply the buttocks and contiguous perineum. 5. The anococcygeal nerves—these nerves arise from S4 to S5 and also perforate the sacrotuberous ligament to supply the skin overlying the coccyx.


Gynecology_Novak

Gynecology_Novak. 5. The anococcygeal nerves—these nerves arise from S4 to S5 and also perforate the sacrotuberous ligament to supply the skin overlying the coccyx. Autonomic Innervation Functionally, the innervation of the pelvic viscera may be divided into an efferent component and an afferent, or sensory, component. In reality, afferent and efferent fibers are closely associated in a complex interlacing network and cannot be separated anatomically. Efferent fibers of the autonomic nervous system, unlike motor fibers in the somatic system, involve one synapse outside the central nervous system, with two neurons required to carry each impulse. In the sympathetic (thoracolumbar) division, this synapse is generally at some distance from the organ being innervated; conversely, the synapse is on or near the organ of innervation in the parasympathetic (craniosacral) division.


Gynecology_Novak

Gynecology_Novak. Axons from preganglionic neurons emerge from the spinal cord to make contact with peripheral neurons arranged in aggregates known as autonomic ganglia. Some of these ganglia, along with interconnecting nerve fibers, form a pair of longitudinal cords called the sympathetic trunks. Located lateral to the spinal column from the base of the cranium to the coccyx, the sympathetic trunks lie along the medial border of the psoas muscle from T12 to the sacral prominence and then pass behind the common iliac vessels to continue into the pelvis on the anterior surface of the sacrum. On the anterolateral surface of the aorta, the aortic plexus forms a lacy network of nerve fibers with interspersed ganglia. Rami arising from or traversing the sympathetic trunks join this plexus and its subsidiaries. Figure 5.9 The presacral nerves.


Gynecology_Novak

Gynecology_Novak. Figure 5.9 The presacral nerves. The ovaries, part of the fallopian tubes, and broad ligament are innervated by the ovarian plexus, a network of nerve fibers accompanying the ovarian vessels and derived from the aortic and renal plexuses. The inferior mesenteric plexus is a subsidiary of the celiac plexus and aortic plexus and is located along the inferior mesenteric artery and its branches, providing innervation to the left colon, sigmoid, and rectum.


Gynecology_Novak

Gynecology_Novak. The superior hypogastric plexus (presacral nerve) is the continuation of the aortic plexus beneath the peritoneum in front of the terminal aorta, the fifth lumbar vertebra, and the sacral promontory, medial to the ureters (Fig. 5.9). Embedded in loose areolar tissue, the plexus overlies the middle sacral vessels and is usually composed of two or three incompletely fused trunks. It contains preganglionic fibers from lumbar nerves, postganglionic fibers from higher sympathetic ganglia and the sacral sympathetic trunks, and visceral afferent fibers. Just below the sacral promontory, the superior hypogastric plexus divides into two loosely arranged nerve trunks, the hypogastric nerves. These nerves course inferiorly and laterally to connect with the inferior hypogastric plexuses (pelvic plexuses), which are a dense network of nerves and ganglia that lie along the lateral pelvic sidewall overlying branches of the internal iliac vessels (Fig. 5.9).


Gynecology_Novak

Gynecology_Novak. The inferior hypogastric plexus includes efferent sympathetic fibers, afferent (sensory) fibers, and parasympathetic fibers arising from the pelvic splanchnic nerves (S2 to S4, nervi erigentes). This paired plexus is the final common pathway of the pelvic visceral nervous system and is divided into three portions, representing distribution of innervation to the viscera: 1. Vesical plexus Innervation: bladder and urethra Course: along vesical vessels 2. Middle rectal plexus (hemorrhoidal) Innervation: rectum Course: along middle rectal vessels 3. Uterovaginal plexus (Frankenh¨auser ganglion) Innervation: uterus, vagina, clitoris, vestibular bulbs Course: along uterine vessels and through cardinal and uterosacral ligaments; sym pathetic and sensory fibers derive from T10, L1; parasympathetic fibers derive from S2 to S4.


Gynecology_Novak

Gynecology_Novak. Course: along uterine vessels and through cardinal and uterosacral ligaments; sym pathetic and sensory fibers derive from T10, L1; parasympathetic fibers derive from S2 to S4. Afferent fibers from the pelvic viscera and blood vessels traverse the same pathways to provide sensory input to the central nervous system. They are involved in reﬂex arcs needed for bladder, bowel, and genital tract function. The afferent fibers reach the central nervous system to have their first synapse within the posterior spinal nerve ganglia.


Gynecology_Novak

Gynecology_Novak. Presacral neurectomy, in which a segment of the superior hypogastric plexus is divided and resected in order to interrupt sensory fibers from the uterus and cervix, is associated with relief of dysmenorrhea secondary to endometriosis in about 50% to 75% of cases in which it was used (18,19). Efferent fibers from the adnexa travel with the ovarian plexus; thus, pain originating from the ovary or tube is not relieved by resection of the presacral nerve. Because this plexus contains efferent sympathetic and parasympathetic nerve fibers intermixed with afferent fibers, disturbance in bowel or bladder function may result. An alternative surgical procedure is resection of a portion of the uterosacral ligaments; because they contain numerous nerve fibers with more specific innervation to the uterus, it is postulated that bladder and rectal function is less vulnerable to compromise (20).


Gynecology_Novak

Gynecology_Novak. An anesthetic block of the pudendal nerve is performed most often for pain relief with uncomplicated vaginal deliveries but may provide useful anesthesia for minor perineal surgical procedures. This nerve block may be accomplished transvaginally or through the perineum. A needle is inserted toward the ischial spine with the tip directed slightly posteriorly and through the sacrospinous ligament. As the anesthetic agent is injected, frequent aspiration is required to avoid injection into the pudendal vessels, which travel with the nerve. The female urinary and genital tracts are closely related, anatomically and embryologically. Both are derived largely from primitive mesoderm and endoderm, and there is evidence that the embryologic urinary system has an important inductive inﬂuence on the developing genital system. About 10% of infants are born with some abnormality of the genitourinary system, and anomalies in one system are often mirrored by anomalies in another system (19).


Gynecology_Novak

Gynecology_Novak. Developmental defects may play a significant role in the differential diagnosis of certain clinical signs and symptoms and have special implications in pelvic surgery (21–26). Thus it is important for gynecologists to have a basic understanding of embryology. Following is a presentation of the urinary system, internal reproductive organs, and external genitalia in order of their initial appearance, although much of this development occurs concurrently. The development of each of these three regions proceeds synchronously at an early embryologic age (Table 5.6). Urinary System Kidneys, Renal Collecting System, Ureters The kidneys, renal collecting system, and ureters derive from the longitudinal mass of mesoderm (known as the nephrogenic cord) found on each side of the primitive aorta. Table 5.6 Development of Genital and Urinary Tracts by Embryologic Age


Gynecology_Novak

Gynecology_Novak. Table 5.6 Development of Genital and Urinary Tracts by Embryologic Age This process gives rise to three successive sets of increasingly advanced urinary structures, each developing more caudal to its predecessor. The pronephros, or “first kidney,” is rudimentary and nonfunctional; it is succeeded by the “middle kidney,” or mesonephros, which is believed to function brieﬂy before regressing. Although the mesonephros is transitory as an excretory organ, its duct, the mesonephric (wolffian) duct,is of singular importance for the following reasons: 1. It grows caudally in the developing embryo to open, for the first time, an excretory channel into the primitive cloaca and the “outside world.” 2. It serves as the starting point for development of the metanephros, which becomes the definitive kidney. 3. It ultimately differentiates into the sexual duct system in the male. 4.


Gynecology_Novak

Gynecology_Novak. It serves as the starting point for development of the metanephros, which becomes the definitive kidney. 3. It ultimately differentiates into the sexual duct system in the male. 4. Although regressing in female fetuses, there is evidence that the mesonephric duct may have an inductive role in development of the paramesonephric or m¨ullerian duct (22).


Gynecology_Novak

Gynecology_Novak. 4. Although regressing in female fetuses, there is evidence that the mesonephric duct may have an inductive role in development of the paramesonephric or m¨ullerian duct (22). The ureteric buds, which sprout from the distal mesonephric ducts, initiate the development of the metanephros; these buds extend cranially and penetrate the portion of the nephrogenic cord known as the metanephric blastema. The ureteric buds begin to branch sequentially, with each growing tip covered by metanephric blastema. Ultimately the metanephric blastema form the renal functional units (the nephrons), whereas the ureteric buds become the collecting duct system of the kidneys (collecting tubules, minor and major calyces, renal pelvis) and the ureters. Although these primitive tissues differentiate along separate paths, they are interdependent on inductive inﬂuences from each other—neither can develop alone.


Gynecology_Novak

Gynecology_Novak. The kidneys initially lie in the pelvis but subsequently ascend to their permanent location, rotating almost 90 degrees in the process as the more caudal part of the embryo in effect grows away from them. Their blood supply, which first arises as branches of the middle sacral and common iliac arteries, comes from progressively higher branches of the aorta until the definitive renal arteries form; previous vessels then regress. The definitive kidneys become functional in the late 7th to early 8th weeks of gestation.


Gynecology_Novak

Gynecology_Novak. The cloaca forms as the result of dilation of the opening to the fetal exterior. During the 7th week of gestation, the cloaca is partitioned by the mesenchymal urorectal septum into an anterior urogenital sinus and a posterior rectum. The bladder and urethra form from the most superior portion of the urogenital sinus, with surrounding mesenchyme contributing to their muscular and serosal layers. The remaining inferior urogenital sinus is known as the phallic or definitive urogenital sinus. Concurrently, the distal mesonephric ducts and attached ureteric buds are incorporated into the posterior bladder wall in the area that will become the bladder trigone. As a result of the absorption process, the mesonephric duct ultimately opens independently into the urogenital sinus below the bladder neck.


Gynecology_Novak

Gynecology_Novak. The allantois, which is a vestigial diverticulum of the hindgut that extends into the umbilicus and is continuous with the bladder, loses its lumen and becomes the fibrous band known as the urachus or median umbilical ligament. In rare instances, the urachal lumen remains partially patent, with formation of urachal cysts, or completely patent, with the formation of a urinary fistula to the umbilicus (23).


Gynecology_Novak

Gynecology_Novak. Genital System Although genetic gender is determined at fertilization, the early genital system is indistinguishable between the two genders in the embryonic stage. This is known as the “indifferent stage” of genital development, during which both male and female fetuses have gonads with prominent cortical and medullary regions, dual sets of genital ducts, and external genitalia that appear similar. Male sexual differentiation is an “active” process, requiring the presence of the SRY gene (gender-determining region), located on the short arm of the Y chromosome. Clinically, gender is not apparent until about the 12th week of embryonic life and depends on the elaboration of testis-determining factor and, subsequently, androgens by the male gonad. Female development is called the “basic developmental path of the human embryo,” requiring not estrogen but the absence of testosterone.


Gynecology_Novak

Gynecology_Novak. The primordial germ cells migrate from the yolk sac through the mesentery of the hindgut to the posterior body wall mesenchyme at about the 10th thoracic level, which is the initial site of the future ovary (Figs. 5.10 and 5.11). Once the germ cells reach this area, they induce proliferation of cells in the adjacent mesonephros and celomic epithelium to form a pair of genital ridges medial to the mesonephros. This occurs during the 5th week of gestation. The development of the gonad is absolutely dependent on this proliferation because these cells form a supporting aggregate of cells (the primitive sex cords) that invest the germ cells and without which the gonad would degenerate.


Gynecology_Novak

Gynecology_Novak. M¨ullerian Ducts The paramesonephric or m¨ullerian ducts form lateral to the mesonephric ducts; they grow caudally and then medially to fuse in the midline. They contact the urogenital sinus in the region of the posterior urethra at a slight thickening known as the sinusal tubercle. Subsequent sexual development is controlled by the presence or absence of testis-determining factor, encoded on the Y chromosome and elaborated by the somatic sex cord cells. Testis-determining factor causes the degeneration of the gonadal cortex and differentiation of the medullary region of the gonad into Sertoli cells.


Gynecology_Novak

Gynecology_Novak. The Sertoli cells secrete a glycoprotein known as anti-m¨ullerian hormone (AMH), which causes regression of the paramesonephric duct system in the male embryo and is the likely signal for differentiation of Leydig cells from the surrounding mesenchyme. The Leydig cells produce testosterone and, with the converting enzyme 5α-reductase, dihydrotestosterone. Testosterone is responsible for evolution of the mesonephric duct system into the vas deferens, epididymis, ejaculatory ducts, and seminal vesicle. At puberty, testosterone leads to spermatogenesis and changes in primary and secondary sex characteristics. Dihydrotestosterone triggers the development of the male external genitalia and the prostate and bulbourethral glands. In the absence of testis-determining factor, the medulla regresses, and the cortical sex cords break up into isolated cell clusters (the primordial follicles).


Gynecology_Novak

Gynecology_Novak. The germ cells differentiate into oogonia and enter the first meiotic division as primary oocytes, at which point development is arrested until puberty. In the absence of AMH, the mesonephric duct system degenerates, although in at least one-fourth of adult women, remnants may be found in the mesovarium (epoophoron, paroophoron) or along the lateral wall of the uterus or vagina (Gartner duct cyst) (24). The paramesonephric duct system subsequently develops. The inferior fused portion becomes the uterovaginal canal, which later becomes the epithelium and glands of the uterus and the upper vagina. The endometrial stroma and myometrium differentiate from surrounding mesenchyme. Figure 5.10 The comparative changes of the female and male during early embryonic development.


Gynecology_Novak

Gynecology_Novak. Figure 5.10 The comparative changes of the female and male during early embryonic development. Figure 5.11 The embryonic development of the female genital tract. The formation of the uterus and vagina. A: The uterus and superior end of the vagina begin to form as the paramesonephric ducts fuse together near their attachment to the posterior wall of the primitive urogenital sinus. B, C: The ducts then zipper together in a superior direction between the 3rd and 5th months. As the paramesonephric ducts are pulled away from the posterior body wall, they drag a fold of peritoneal membrane with them, forming the broad ligaments of the uterus. A–C: The inferior end of the vagina forms from the sinovaginal bulbs on the posterior wall of the primitive urogenital sinus. The cranial unfused portions of the paramesonephric ducts open into the celomic (future peritoneal) cavity and become the fallopian tubes.


Gynecology_Novak

Gynecology_Novak. The cranial unfused portions of the paramesonephric ducts open into the celomic (future peritoneal) cavity and become the fallopian tubes. The fusion of the paramesonephric ducts brings together two folds of peritoneum, which become the broad ligament and divide the pelvic cavity into a posterior rectouterine and anterior vesicouterine pouch or cul-de-sac. Between the leaves of the broad ligament, mesenchyme proliferates and differentiates into loose areolar connective tissue and smooth muscle.