Sepsis

Sepsis. Of these, 35/53 (66%) of the patients had positive FDG-PET/CT findings, and 13/53 (25%) of the patients had treatment modified based on imaging results, which included surgery (9/13) and placement of drainage catheters (4/13). Although the majority of infections identified were musculoskeletal (19/53, 38%), the second most common site of infection was in the chest (13/53, 25%). The presence of liver cirrhosis was the only variable significantly associated with the likelihood of negative PET data (P = . 005). Kluge et al [10] performed a single-center 6 year retrospective study of critically ill patients with severe sepsis or septic shock of unknown origin. Eighteen patients underwent initial workup, including unrevealing chest radiography followed by FDG-PET/CT (without any other prior cross-sectional imaging). Of these, 14/18 (78%) of the patients had positive FDG-PET/CT findings, of whom 3/18 (17%) of the patients were false positives, 11/18 (61%) of the patients were true positives, and 6/18 (33%) of the patients had treatment modified based on imaging results, which included surgery and initiation/prolongation of antibiotic therapy. There were no false negatives (100% NPV). Brondserud et al [11] performed a single-center retrospective study of 157 patients with 165 separate episodes of bacteremia of unknown origin who had also undergone FDG-PET/CT as part of the workup for infection or sepsis. FDG-PET/CT was able to detect the site of infection in 93/165 scans (56.4%). It was the first modality to identify the site of infection in 41.1% of cases, led to changes in antimicrobial therapy in 14.7% of patients, and resulted in a new infection-related diagnosis unrelated to bacteremia in 9.8% of episodes. FDG-PET/CT had a high clinical impact in 47.3% of cases and was independent of the duration of the preceding antimicrobial treatment as well as the number of days of bacteremia.


Sepsis

Sepsis. Pijl et al [12] performed a single-center retrospective cohort study of all ICU patients with culture-proven blood stream infection over a 10 year period who had undergone FDG-PET/CT specifically to assess for source of infection after an initial negative conventional workup. Of the 30 patients included in the study, FDG-PET/CT identified a source of infection in 70% of patients and had a sensitivity of 90.9% and a specificity of 87.5% with discharge diagnosis serving as the reference standard. The most common sources of infection found were pneumonia and septic arthritis. The overall PPV was 95.2%, and NPV was 77.8% for identifying a focus of infection. Of the positive FDG-PET/CTs, 52% identified a new infectious focus that led to treatment modifications such as abscess drainage, removal of infected material, or change in antimicrobial therapy. FDG-PET/CT still resulted in treatment changes in an additional 14% who already had a known infectious focus. Given that PET/CT does not provide the same degree of anatomic localization as a dedicated diagnostic dose CT, PET/CT is not considered useful as the next imaging modality after chest radiograph. Therefore, it should only be considered for use after source localization with CT has failed. Fluoroscopy Contrast Enema There are no data to support the use of fluoroscopy contrast enema without contrast as a diagnostic imaging study in the diagnosis of sepsis. Fluoroscopy Upper GI Series with Small Bowel Follow-Through There are no data to support the use of upper GI series with small bowel follow-through as a diagnostic imaging study in the diagnosis of sepsis. MRI Abdomen and Pelvis Without and With IV Contrast There are no data to support the use of MRI abdomen and pelvis without and with IV contrast as the next diagnostic imaging study after normal, equivocal, or nonspecific chest radiography in the diagnosis of sepsis. The majority of Sepsis


Sepsis

Sepsis. patients with sepsis are too unstable to undergo a relatively long imaging procedure especially with the availability of alternate imaging modalities that are shorter and easier to obtain. However, in certain situations such as targeting a specific source of clinically suspected infection, MRI has been shown to be useful. Given that perianal sepsis occurs in up to 10% of neutropenic patients, Ashkar et al [14] performed a retrospective review of neutropenic patients from hematologic malignancy who were given the diagnosis of perianal sepsis. Of the 19 included patients, 9 patients underwent pelvic MRI without and with IV contrast. Of these, 88% (8/9) of the patients were found to have a focal collection compatible with a perianal abscess. This resulted in intraoperative drainage of the fluid collection in 6 patients, of whom 80% (5/6) of patients were confirmed to have a purulent draining cavity intraoperatively; 20% (1/6) of the patients was deemed to be a false-positive result. MRI Abdomen and Pelvis Without IV Contrast There are no data to support the use of MRI abdomen and pelvis without IV contrast as a diagnostic imaging study in the diagnosis of sepsis. MRI Chest Without and With IV Contrast Although MRI can readily detect pulmonary and pleural infection, there are no data to support the use of MRI chest without and with IV contrast as the next diagnostic imaging study after normal, equivocal, or nonspecific chest radiography in the diagnosis of sepsis. MRI Chest Without IV Contrast Although MRI can readily detect pulmonary and pleural infection, there are no data to support the use of MRI chest without IV contrast as the next diagnostic imaging study after normal, equivocal, or nonspecific chest radiography in the diagnosis of sepsis. Nuclear Medicine Scan Gallbladder There are no data to support the use of nuclear medicine scan gallbladder as a diagnostic imaging study in the diagnosis of sepsis.


Sepsis

Sepsis. Radiography Abdomen Although abdominal radiography is portable and rapidly acquired (which is of obvious benefit for a suspected or confirmed septic patient), it rarely provides a definitive diagnosis in the setting of sepsis. It may provide information that increases the probability of an abdominal source such as pneumoperitoneum, but these findings would be either suspected by physical examination or at least partially visualized on chest radiography and would still necessitate further evaluation with CT or US regardless [15,16]. US Abdomen Abdominal/pelvic US is often chosen as an imaging modality in patients of child-bearing age in the evaluation of suspected intraabdominal sepsis. Potential diagnoses responsible for sepsis in this setting can be divided into gynecological causes (such as endometritis, salpingitis, oophoritis, tubo-ovarian abscess, pelvic peritonitis) and nongynecological causes (such as acute appendicitis, diverticulitis, ileitis/colitis, epiploic appendagitis, and urological causes), which can be assessed to varying degrees on US [17]. In the setting of urosepsis, US is often useful as the first imaging modality of choice, in part because of its portability and rapid acquisition, which is of obvious benefit for a suspected or confirmed septic patient [15,16]. Based on recent studies, there is potential value in employment of artificial intelligence techniques to enhance the value of abdominal US in the setting of sepsis, but this discussion is beyond the scope of this topic. Sorenson et al [18] performed a retrospective review of 221 patients with first-time bacteremia suspected to be urosepsis. Of these, 116/221 (52%) of the patients underwent further evaluation with either abdominal US or abdomen/pelvis CT. Major abnormalities were found in 37/115 (32%) of patients and most commonly included pyonephrosis and renal calculi. Of these, 15/115 (13%) of the patients underwent urological intervention as a result of imaging findings.


Sepsis

Sepsis. Follow-up of 105 patients who did not undergo initial imaging revealed that 10/105 (9.5%) of the patients were readmitted the following year with urosepsis; of these patients, imaging by US or CT was indicated for 6/10, and a major abnormality was detected in 3/6 imaged patients. Hoddick et al [13] in a prospective study of 12 patients with urosepsis who were evaluated with both US and CT. Of these, 6/12 of the patients had renal abscesses, of whom 6/6 (100%) of the patients were identified on both US and contrast-enhanced CT. One patient had multiple perirenal abscesses, and another patient had a gas-forming perinephric abscess that were both missed by US but seen on CT. Sepsis WBC Scan Abdomen and Pelvis When initial cross-sectional imaging is inconclusive in determining the origin of sepsis, radiolabeled WBC scans may be useful as a subsequent imaging study in providing diagnostic information. There is a relative paucity of recent literature regarding the usefulness of WBC scans in the setting of sepsis, and the majority of studies were performed before the routine use of SPECT/CT, which improves the accuracy of radiolabeled WBC scans by co- registering scintigraphic and CT data [19]. Carter et al [20] performed a retrospective review on the usefulness of Indium-111-tagged WBC scan and US in 45 patients with suspected intraabdominal sepsis but without localizing abdominal signs, of whom 22 were ultimately determined to have intraabdominal abscesses. Indium-111-tagged WBC scan correctly identified the intraabdominal abscess in 21/22 patients (sensitivity 95%) and incorrectly predicted abscesses in 2 patients (specificity 91%). All patients had a concurrent US performed and Indium-111-tagged WBC scan was shown to be more sensitive but less specific (US sensitivity was 45% and specificity was 100%).


Sepsis

Sepsis. Baba et al [21] performed a retrospective review of the 45 Indium-111-tagged WBC scans that were performed in the aforementioned study by Carter et al in order to evaluate the usefulness of having performed these examinations. Of these, 34/45 (76%) of the studies were determined to be helpful in furthering patient management, even though only half (50%) of the 34 studies were positive, and 8/45 (18%) were considered to be unhelpful in furthering patient management, and 3/45 (6%) were considering to be misleading and led to inappropriate treatment from study results. Uslu et al [22] performed a prospective study involving 15 women with clinically suspected pyogenic pelvic inflammatory disease who underwent Tc-99m-HMPAO (hexamethylpropyleneamine oxime)-tagged WBC scan. All patients had previously undergone another study by either US or CT before the WBC scan. Tc-99m-HMPAO- tagged WBC correctly identified pyogenic pelvic inflammatory disease in all 5 surgically confirmed cases (sensitivity 100%) and incorrectly reported pyogenic pelvic inflammatory disease in 1/10 surgically confirmed negative cases (specificity 90%). Given that the above-mentioned studies are from older literature before the routine use of cross-sectional CT studies, WBC scans are no longer considered useful as the next imaging modality after chest radiograph, given that a WBC scan cannot provide exact anatomic localization in the manner comparable to a CT scan. Therefore, it should only be used after source localization with CT has failed. Sepsis examination is usually appropriate or may be appropriate as the next imaging study. The panel did not agree on recommending CT abdomen and pelvis without IV contrast or CT chest abdomen and pelvis without IV contrast as the next imaging study for this clinical scenario. There is insufficient medical literature to conclude whether or not these patients would benefit from these modalities. Imaging with the mentioned examinations in this patient population is controversial but may be appropriate.


Ovarian Cancer Screening

Ovarian Cancer Screening.  Introduction/Background There has been much debate about the role of imaging in ovarian cancer screening based on currently available evidence [1]. Ovarian cancer has low disease prevalence, yet is the leading cause of mortality due to gynecologic malignancy in women in the United States [2]. It is estimated that there will be 22,440 new cancer diagnoses and 14,080 cancer deaths in 2017 [2]. The high mortality rate observed is largely due to late detection, as it is commonly discovered only after its widespread dissemination. Metastatic disease is present in 60% of cases at the time of diagnosis and is associated with a low 5-year relative survival rate of 28% [2]. Only 15% of women have organ-confined disease at the time of detection, and these women have a substantially higher 5-year relative survival rate (92%) [2], suggesting that screening could be of benefit if aggressive cancers can be reliably detected at earlier stages. The average lifetime risk for developing ovarian cancer for a woman in the United States is approximately 1.3% [2]. Women with certain risk factors are known to be at increased risk, including presence of BRCA1 or BRCA2 mutations, strong family history (ie, first-degree relative, particularly if premenopausal at the time of diagnosis), nulliparity, lack of breastfeeding, lack of hormonal contraception use, and postmenopausal status [9]. Among all risk factors, a genetic predisposition is associated with the highest increase in cancer risk. A recent meta-analysis projected that 20-year-old BRCA1 and BRCA2 mutation carriers have 39% and 16% mean cumulative risks of developing ovarian cancer, respectively, by age 70 [10]. At present, risk reduction in women with a strong genetic predisposition to ovarian cancer centers on bilateral salpingo-oophorectomy [11].


Ovarian Cancer Screening

Ovarian Cancer Screening. By mathematically modeling the behavior of ovarian cancers in hypothetical populations of BRCA mutation carriers and average-risk patients, researchers have gained insight into their natural history and have investigated a potential role for screening [3,4]. Based on their findings, current screening tools are expected to have low effectiveness because of the tendency for small cancers to spread rapidly [3,4]. Brown and Palmer [3], when Reprint requests to: publications@acr.org Ovarian Cancer Screening modeling serous cancers in high-risk patients, projected that an annual screening tool for ovarian cancer would need to detect tumors as small as 0.5 cm in diameter in order to achieve a 50% mortality reduction. After evaluating the current literature on this topic, there is no clear evidence to support screening women of average risk (no personal history, no family history, no known or suspected genetic predisposition, and no elevated CA-125). However, this document provides an update on areas of investigation that may support a future role for imaging and serum biomarkers in special cases. Overview of Imaging Modalities Most of the peer-reviewed imaging literature on ovarian cancer screening to date has evaluated the use of pelvic ultrasound (US), as it is generally considered the first-line imaging modality for evaluation of the adnexa. US is particularly attractive as a potential screening modality as it is inexpensive and does not expose patients to ionizing radiation. Other cross-sectional imaging methods, including magnetic resonance imaging (MRI), fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET), computed tomography (CT), and FDG-PET/CT, have no known or foreseeable role in screening. Attention has also been directed to the role of CA-125 (a widely known serum tumor biomarker) for screening, either alone or in combination with imaging (eg, US and CA-125).


Ovarian Cancer Screening

Ovarian Cancer Screening. When evaluating the use of an imaging modality for screening, an important metric to consider is positive predictive value (PPV), which is defined as the number of true-positive cases divided by the total number of test- positive cases. Unlike the sensitivity and specificity of a diagnostic test, PPV incorporates both test performance and disease prevalence. A minimum PPV of 10% has been suggested as necessary for an ovarian cancer screening tool [9,12]. This implies that at least one cancer should be diagnosed in every 10 patients who undergo salpingo- oophorectomy for suspicion of malignancy. Given the low prevalence of ovarian cancer, very high specificity is needed for a successful screening tool. At an assumed prevalence of one case per 2,500 postmenopausal women per year, a test with perfect sensitivity (100%) would require a specificity of 99.6% to achieve a 10% PPV, and a test with 50% sensitivity would require an even higher specificity of 99.8% [9,12-14]. Discussion of Procedures by Variant Variant 1: Ovarian cancer screening. Premenopausal. Average risk. To our knowledge, the relevant literature on ovarian cancer screening in average-risk women is limited to studies in postmenopausal women. US There is currently no evidence to support the use of US or color Doppler for ovarian cancer screening in premenopausal women without risk factors. Most studies discussed in this document have addressed the use of transvaginal US. In general, transabdominal US should be reserved for women in whom transvaginal US is not technically feasible, or used as a complement to transvaginal US. CT There is currently no evidence to support the use of CT for ovarian cancer screening in premenopausal women without risk factors. MRI There is currently no evidence to support the use of MRI for ovarian cancer screening in premenopausal women without risk factors.


Ovarian Cancer Screening

Ovarian Cancer Screening. FDG-PET/CT There is currently no evidence to support the use of FDG-PET/CT for ovarian cancer screening in premenopausal women without risk factors. Variant 2: Ovarian cancer screening. Postmenopausal. Average risk. US US has been the most heavily investigated imaging modality for ovarian cancer screening to date, both alone and in conjunction with biomarker screening of serum CA-125. Most studies discussed in this document have addressed the use of transvaginal US. In general, transabdominal US should be reserved for women in whom transvaginal US is not technically feasible, or used as a complement to transvaginal US. A recent meta-analysis [15] of 10 randomized trials of ovarian cancer screening using US and/or serum CA-125 measurements found that the included trials did not demonstrate a significant reduction in mortality. Below we describe the studies that are Ovarian Cancer Screening most relevant for decision making concerning ovarian cancer screening in average-risk postmenopausal women. The majority were designed to accrue a dominant population of average-risk postmenopausal women. However, across studies, exclusion criteria intended to exclude high-risk women were heterogeneous. In the University of Kentucky Ovarian Cancer Screening Study, investigators deliberately also included a subset of premenopausal high-risk women, as detailed below. Of note, the methodologic detail provided in the studies described below does not allow for uniform determination of the use, or potential benefits, of color Doppler. Therefore, the benefits of US performed with, versus without, color Doppler cannot be determined. Shizuoka District (Japan) Trial In 2008, Kobayashi et al [17] published a randomized controlled trial in which postmenopausal women were randomized to a control group (n = 40,799) or to five screening rounds of CA-125 and US (n = 41,688). US was predominantly performed using a transvaginal approach.


Ovarian Cancer Screening

Ovarian Cancer Screening. At US, ovaries were considered suspicious for malignancy if ovarian size was >4 cm and a complex morphology was apparent. In the screening group, further management ranged from annual follow-up to surgical intervention, depending on combined test results. Salient trial findings were 2-fold. First, ovarian cancer prevalence was lower (0.31/1,000) than in an expected United States population. Second, a statistically significant shift in stage distribution was not achieved. Ovarian Cancer Screening Lu, Skates, Hernandez, and Colleagues In 2013, Lu et al [22] reported results from a single-arm prospective trial of ovarian cancer screening in 4,051 postmenopausal women using the Risk of Ovarian Cancer Algorithm (ROCA) score based on serum CA-125 measurements (described below). In this trial, women with ROCA scores indicating intermediate risk (risk of ovarian cancer between 1 in 2,000 and 1 in 500) had a repeat CA-125 measurement in 3 months, and women with ROCA scores indicating elevated risk (>1 in 500) were referred for transvaginal US and gynecologic oncology consultation. After 11 years of follow-up, 10 women underwent surgery based on US findings, and 4 of these women were found to have invasive ovarian cancer (PPV, 40%). Specificity was 99.9%. These results support the notion that assessment of changing levels in biomarkers over time may be a more useful screening tool than single values, such as those used in the PLCO trial, and can improve PPV and specificity. However, this trial was not designed to assess mortality outcomes. United Kingdom Collaborative Trial of Ovarian Cancer Screening The United Kingdom Collaborative Trial of Ovarian Cancer Screening [23,24] is the largest randomized controlled trial of ovarian cancer screening to date, with over 200,000 postmenopausal women randomized to either a control group, multimodal screening (ie, annual CA-125 with transvaginal US as a follow-up test), or annual transvaginal US alone.


Ovarian Cancer Screening

Ovarian Cancer Screening. US results were considered abnormal if ovaries demonstrated a complex morphology or had simple cysts >60 mL or if ascites was present [24]. Rather than using standard single cutoffs for CA-125 positivity, CA-125 results were designated based on the ROCA algorithm described by Menon et al [25] in earlier work. This algorithm incorporates patient age and CA-125 trends to triage further management, and it is expected to improve CA-125 test performance, particularly its PPV and specificity [25]. MRI To our knowledge, there have been no trials evaluating the use of MRI for ovarian cancer screening in women at average risk. Although MRI is a valuable tool for characterizing adnexal masses that are indeterminate based on US features [26], there has been little interest in its use as a population screening tool given its cost and unclear advantage. CT To our knowledge, there have been no trials evaluating the use of CT for ovarian cancer screening in women at average risk. CT is routinely used for ovarian cancer staging to assess for distant metastases, but it has limited use in the evaluation of the adnexa given its limited ability to distinguish between benign and malignant lesions. For example, in a study of 2,869 postmenopausal women undergoing CT screening colonography [27], 118 (4.1% of the cohort) had incidentally detected adnexal lesions noted at interpretation. Of these, 80 were referred for additional imaging workup and/or surgery. In the 26 women who underwent surgical excision, no ovarian cancers were identified. Furthermore, four women in the cohort subsequently developed ovarian cancer after a negative CT evaluation. The limited discriminatory ability of CT renders it impractical for use as a screening tool in this setting. FDG-PET/CT To our knowledge, there have been no trials evaluating the use of FDG-PET/CT for ovarian cancer screening in women at average risk.


Ovarian Cancer Screening

Ovarian Cancer Screening. Although FDG-PET/CT is an important oncologic imaging tool for cancer staging and detection of recurrence, it has no clear value for detecting ovarian cancer in asymptomatic individuals. In a Ovarian Cancer Screening systematic review of imaging modalities for preoperative evaluation of adnexal lesions, the sensitivity of PET was substantially lower than that of US or MRI [28], possibly because of the composition of ovarian neoplasms, many of which tend to be predominantly cystic with small solid components that may be below the size threshold for detection by PET. Variant 3: Ovarian cancer screening. Premenopausal. High risk (personal history or family history or known or suspected genetic predisposition or elevated CA-125). US Most studies discussed in this document have addressed the use of transvaginal US. In general, transabdominal US should be reserved for women in whom transvaginal US is not technically feasible, or used as a complement to transvaginal US. The University of Kentucky Ovarian Cancer Screening Study cohort [20] also included premenopausal women with a family history of ovarian cancer. The study results were reported in aggregate for patients with and without a family history of ovarian cancer. However, the authors note that there was no significant difference in the incidence of malignant or benign ovarian tumors between these groups. Although the results of this single-arm study were promising, a definitive mortality reduction has not been observed in randomized controlled trials [18,23]. MRI To our knowledge, there are no trials for the use of MRI as an ovarian cancer screening tool in high-risk women. MRI is unlikely to be investigated as a screening tool. CT To our knowledge, there are no trials of the use of CT as an ovarian cancer screening tool in high-risk women.


Ovarian Cancer Screening

Ovarian Cancer Screening. CT has a limited role in the evaluation of adnexal lesions and would be an impractical screening modality because of its poor discriminatory ability between benign and malignant adnexal lesions and the associated risks of ionizing radiation. FDG-PET/CT To our knowledge, there have been no trials evaluating the use of FDG-PET/CT as an ovarian cancer screening tool in high-risk women. FDG-PET/CT has poor performance in this setting and is impractical as a screening modality. Ovarian Cancer Screening Variant 4: Ovarian cancer screening. Postmenopausal. High risk (personal history or family history or known or suspected genetic predisposition or elevated CA-125). US Most studies discussed in this document have addressed the use of transvaginal US. In general, transabdominal US should be reserved for women in whom transvaginal US is not technically feasible, or used as a complement to transvaginal US. To our knowledge, randomized controlled trials analogous to those in average-risk populations have not been conducted in definitively high-risk populations. Several related studies have been reported, all relatively small in sample size and most of which include a mix of premenopausal and postmenopausal women at high risk [29-33]. In 2006, Lacey et al [35] performed a secondary analysis of PLCO data to compare, within the screening arm, differences in screening outcomes (after the first four rounds of screening) between women of varying risk for ovarian cancer. Risk was classified based on personal history of breast cancer and family history of breast or ovarian cancer. Although the PPV of screening was marginally higher for women in specified moderate- and high-risk groups compared to those at average risk (PPV of 1.3% and 1.6% in the moderate- and high-risk groups, respectively, compared to 0.7% in the average-risk group), this difference was not statistically significant.


Ovarian Cancer Screening

Ovarian Cancer Screening. In 2016, Lai et al [36] published a subgroup analysis of PLCO data to determine whether annual screening with pelvic US and serum CA-125 reduced ovarian cancer mortality in a subgroup of women with a first-degree relative with breast or ovarian cancer. The authors compared outcomes for 11,293 women in the screening group and 11,062 women in the control group, who were followed for a minimum of 10 years. As seen in the parent PLCO study, there was no significant difference in ovarian cancer mortality between the screening and control groups. There was evidence of a stage shift and improved survival among patients with ovarian cancer in the screening group (relative risk, 0.66; 95% CI, 0.47-0.93). The authors acknowledged the potential for standard epidemiologic biases to affect their results, despite specific methodologic measures taken, and emphasized the need for further related investigation in high-risk individuals. MRI To our knowledge, there are no trials for the use of MRI as an ovarian cancer screening tool in high-risk women. MRI is unlikely to be investigated as a screening tool. CT To our knowledge, there are no trials of the use of CT as an ovarian cancer screening tool in high-risk women. CT has a limited role in the evaluation of adnexal lesions and would be an impractical screening modality because of its poor discriminatory ability between benign and malignant adnexal lesions and the associated risks of ionizing radiation. Ovarian Cancer Screening FDG-PET/CT To our knowledge, there are no trials of the use FDG-PET/CT as an ovarian cancer screening tool in high-risk women. FDG-PET/CT has poor performance in this setting and is impractical as a screening modality. Summary of Recommendations Ovarian cancer screening is not recommended for average-risk premenopausal women. Ovarian cancer screening is not recommended for average-risk postmenopausal women, as randomized controlled trials have not demonstrated a definitive mortality benefit in this population.


Chronic Elbow Pain

Chronic Elbow Pain.  Imaging plays an important role in assessment of chronic elbow pain. Electromyography assists in the workup related to nerve symptoms. Management for epicondylalgia and osteoarthritis includes conservative measures such as rest, activity modification, analgesia, physical therapy, and corticosteroid injections. Surgery may be indicated for more severe or refractory cases and cases of collateral ligament injury, biceps injury, cubital tunnel syndrome, or osteochondral abnormalities. Special Imaging Considerations Stress radiographs to detect medial joint line opening and/or asymmetry to the contralateral elbow are available to evaluate valgus instability of the elbow. OR aPenn State Milton S. Hershey Medical Center, Hershey, Pennsylvania. bPanel Chair, VA San Diego Healthcare System, San Diego, California. cPanel Vice- Chair, University of Washington, Seattle, Washington. dWeill Cornell Medical College, New York, New York. eUniversity of California San Francisco, San Francisco, California. fMoffitt Cancer Center and University of South Florida Morsani College of Medicine, Tampa, Florida; MSK-RADS (Bone) Committee. gVA San Diego Healthcare System, San Diego, California. hMayo Clinic Arizona, Phoenix, Arizona. iUniversity of Texas Health Science Center, Houston, Texas; Committee on Emergency Radiology-GSER. jThe Centers for Advanced Orthopaedics, George Washington University, Washington, DC and Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland; American Academy of Orthopaedic Surgeons. kUniversity of Wisconsin School of Medicine & Public Health, Madison, Wisconsin. lPenn State Milton S. Hershey Medical Center, Hershey, Pennsylvania, Primary care physician. mThe University of Texas MD Anderson Cancer Center, Houston, Texas; Commission on Nuclear Medicine and Molecular Imaging. nSpecialty Chair, University of Kentucky, Lexington, Kentucky.


Chronic Elbow Pain

Chronic Elbow Pain. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Chronic Elbow Pain Discussion of Procedures by Variant Variant 1: Chronic elbow pain. Initial imaging. 3-Phase Bone Scan Elbow There is limited evidence to support the use of 3-phase bone scan as the initial imaging study for the evaluation of chronic elbow pain. CT Arthrography Elbow There is limited evidence to support the use of CT arthrography elbow as the initial imaging study for the evaluation of chronic elbow pain. CT Elbow There is limited evidence to support the use of CT elbow as the initial imaging study for the evaluation of chronic elbow pain. MR Arthrography Elbow There is limited evidence to support the use of MR arthrography elbow as the initial imaging study for the evaluation of chronic elbow pain. MRI Elbow There is limited evidence to support the use of MRI elbow as the initial imaging study for the evaluation of chronic elbow pain. Radiography Elbow Radiographs are beneficial as the initial imaging for chronic elbow pain. Radiographs may show intra-articular bodies, heterotopic ossification, osteochondral lesion, soft tissue calcification, occult fracture, or osteoarthritis. Radiographs complement subsequent MRI elbow examination [4]. Radiographs have been shown to aide the diagnosis of valgus instability [5] and ulnar collateral ligament (UCL) injury [6]. Comparison with the asymptomatic side is often useful [7]. US Elbow There is limited evidence to support the use of ultrasound (US) elbow as the initial imaging study for the evaluation of chronic elbow pain. Variant 2: Chronic elbow pain with mechanical symptoms such as locking, clicking, or limited range of motion.


Chronic Elbow Pain

Chronic Elbow Pain. Suspect intra-articular pathology such as osteocartilaginous body, osteochondral lesion, or synovial abnormality. Radiographs normal or nonspecific. Next imaging study. 3-Phase Bone Scan Elbow There is limited evidence to support the routine use of 3-phase bone scan elbow for evaluation of osteochondral bodies, osteochondral lesions, or synovial abnormalities. However, the early phase of a 3-phase bone scan can identify the inflammatory component of heterotopic ossification. The delayed images demonstrate increased tracer uptake due to bone formation [8,9]. CT Arthrography Elbow CT arthrography elbow is useful in the assessment of heterotopic ossification, loose bodies, and osteoarthritis. CT elbow has a sensitivity and specificity of 93% and 66% for detection of loose bodies [10]. It has a reported accuracy of 79% for the detection of loose bodies and 76% for osteophytes [10]. However, small intra-articular bodies may be obscured by contrast. CT arthrography is helpful for evaluation of osteochondral lesion stability [11]. CT Elbow CT elbow is useful in the assessment of heterotopic ossification, loose bodies, and osteophytosis. CT elbow has a sensitivity and specificity of 93% and 66% for the detection of loose bodies [10]. CT elbow without intravenous (IV) contrast is less useful than CT arthrography elbow for the assessment of osteochondral lesion stability. MR Arthrography Elbow MRI arthrography elbow is useful for detection of intra-articular bodies, with a reported sensitivity of 100% and a specificity of 67% [12]. MR arthrography elbow also plays an important role in evaluation of osteochondral lesion stability [13,14]. MRI may also show the presence of enlarged synovial plica, which can result in symptoms of locking and/or pain with extension [15]. However, MR arthrography elbow is limited in the detection of cartilage Chronic Elbow Pain abnormalities. Accuracy is reported as 45% for the radius, 64% for the capitellum, 18% for the ulna, and 27% for the trochlea [16].


Chronic Elbow Pain

Chronic Elbow Pain. MRI Elbow MRI elbow may detect loose bodies, and this is enhanced in the presence of joint fluid. Thus, T2-weighted images are recommended for the evaluation of loose bodies in the elbow [17]. MRI may also show the presence of enlarged plica, which can result in symptoms of locking and/or pain with extension [15]. MRI is often suggested as the initial study to assess for osteochondral lesion [12,17]. MRI is less sensitive than radiographs in the detection of heterotopic ossification/calcification [18]. Similar to MR arthrography, MRI elbow is limited in the evaluation of cartilage defects [16]. US Elbow Although US may demonstrate early-stage osteochondral lesions and medial epicondylar fragmentation [10], the details of an osteochondral lesion are better defined by CT arthrography or MR arthrography. Because of shadowing, evaluation of heterotopic ossification and loose bodies is limited on US. Variant 3: Chronic elbow pain. Suspect occult stress fracture or other bone abnormality. Radiographs normal or nonspecific. Next imaging study. 3-Phase Bone Scan Elbow Bone scan is extremely sensitive for detection of stress fractures and trauma related fractures [19-21]. Radiopharmaceutical uptake occurs in areas of active bone turnover, and thus, imaging may be positive in the presymptomatic stage of stress injuries [20]. CT Arthrography Elbow There is limited evidence to the support the use of CT arthrography elbow for the detection of occult fractures following radiographs. CT Elbow CT elbow is helpful in identifying complex fracture patterns, the origin of dislocated fragments, and positions of displaced fragments [22]. However, it has poor sensitivity in the detection of early stress fractures [20]. MR Arthrography Elbow There is limited evidence to the support the use of MR arthrography elbow for the detection of occult fractures following radiographs. MRI Elbow MRI is as sensitive as 3-phase bone scan for detection of stress fractures [20].


Chronic Elbow Pain

Chronic Elbow Pain. MRI findings include bone marrow edema and/or periosteal fluid at the site of abnormality [20]. MRI elbow has the advantage of demonstrating associated soft tissue injuries. US Elbow US can demonstrate a lipohemarthrosis in children with occult elbow fractures [23]. However, poor penetration of sound through the bone limits characterization of fractures. Variant 4: Chronic elbow pain. Suspect chronic epicondylalgia or tendon tear. Refractory to empirical treatment. Radiographs normal or nonspecific. Next imaging study. 3-Phase Bone Scan Elbow Although there is limited evidence to support the routine use of 3-phase bone scan in this setting, bone scans can detect chronic epicondylalgia [24]. CT Arthrography Elbow There is limited evidence to the support the use of CT arthrography elbow for the detection of tendon tears or chronic epicondylalgia. CT Elbow There is limited evidence to the support the use of CT elbow for detection of tendon tears or chronic epicondylalgia. MR Arthrography Elbow MR arthrography does not add additional information compared with noncontrast MRI for the diagnosis of biceps tendon tear or chronic epicondylalgia [25]. Chronic Elbow Pain MRI Elbow MRI has high inter- and intraobserver reliability for the diagnosis of epicondylalgia [26]. It also has a sensitivity of 90% to 100% and a specificity of 83% to 100% [27]. The most specific findings of medial epicondylalgia include intermediate to high T2 signal or high T2 signal within the common flexor tendon and paratendinous soft tissue edema [28]. MRI has the benefit of demonstrating associated findings in epicondylalgia, including radial collateral and lateral UCL injuries [26]. MRI may also facilitate surgical planning [29]. MRI is useful for the diagnosis of biceps tendon injury. Sensitivity and specificity are reported at 92.4% and 100%, respectively, in detecting distal biceps tendon ruptures and 59.1% and 100%, respectively for partial tears [30].


Chronic Elbow Pain

Chronic Elbow Pain. US Elbow US elbow has moderate agreement with MR elbow for the diagnosis and grading of common extensor tendon tears. US sensitivity, specificity, and accuracy are reported at 64.25%, 85.19%, and 72.73%, respectively [31]. Recently, sonoelastography has shown more promising outcomes for detection of medial epicondylalgia with a sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 95.2%, 92%, 93.5%, 90.9%, and 95.8%, respectively [32]. Another new technique, superb microvascular imaging, can be used to detect subtle low blood flow. The combination of superb microvascular imaging with conventional US performed best for the diagnosis of epicondylalgia, with sensitivity of 94%, specificity of 98%, accuracy of 96% [33]. US is also useful for detection of biceps tendon abnormalities. It performs similar to slightly better than MRI for the diagnosis of distal biceps brachii tendon tear [34]. Reports show 95% sensitivity, 71% specificity, and 91% accuracy for the diagnosis of complete versus partial distal biceps tendon tears with US [35]. Variant 5: Chronic elbow pain. Suspect collateral ligament tear. Radiographs normal or nonspecific. Next imaging study. 3-Phase Bone Scan Elbow There is limited evidence to support the routine use of 3-phase bone scan for the diagnosis of collateral ligament injury following radiographs. CT Arthrography Elbow CT arthrography has a sensitivity of 86%. The sensitivity for full-thickness tears and partial tears is reported at 100% and 71%, respectively. The overall specificity is 91% [36]. CT Elbow There is limited evidence to support the routine use of CT elbow for the diagnosis of collateral ligament injury following radiographs. MR Arthrography Elbow MR arthrography elbow is accurate for the diagnosis of collateral ligament injuries [37]. At 3T, it is more accurate than noncontrast MRI [38]. The reported sensitivity, specificity, and accuracy for UCL tears are 81%, 91%, and 88%, respectively [39].


Chronic Elbow Pain

Chronic Elbow Pain. MR arthrography may also assist in differentiation between partial and complete UCL tear [40,41]. Presence of soft tissue and bone marrow edema occurs more often in symptomatic patients [42]. Additionally, a more distal ligamentous insertion of the UCL (T sign) has recently been suggested to result from repetitive overhead activity and injury rather than representing a normal anatomic variant [42]. In patients with posterolateral rotatory instability, MR arthrography can assess the integrity of the ulnar band of the radial collateral ligament [43] and demonstrate radiocapitellar incongruity [44]. MRI Elbow A 3T MR arthrography is more accurate than noncontrast MRI elbow for detection of collateral ligament injuries [38]. Radiography Elbow Stress View Measurement of medial joint space opening on stress radiographs correlates with severity of UCL injury in throwing athletes [6]. Additionally, medial joint vacuum phenomenon on valgus stress radiographs is specific for UCL injury [45]. However, radiographs do not directly provide information on the location of collateral ligament injury or associated soft tissue injuries as can be done on MR arthrography. Chronic Elbow Pain US Elbow For full-thickness UCL tears, conventional US has a sensitivity of 79%, a specificity of 98%, and an accuracy of 95% (38). For partial thickness UCL tears, conventional US has a sensitivity of 77%, a specificity of 94%, and an accuracy of 90% (38). Stress US can accurately detect UCL tears when there is medial joint gapping [46,47]. The sensitivity and specificity of valgus stress US for all UCL tears is 96% and 81%, respectively [36]. Variant 6: Chronic elbow pain. Suspect nerve abnormality. Radiographs normal or nonspecific. Next imaging study. 3-Phase Bone Scan Elbow There is limited evidence to support the routine use of 3-phase bone scan elbow for nerve abnormalities at the elbow following radiographs.


Chronic Elbow Pain

Chronic Elbow Pain. CT Arthrography Elbow There is limited evidence to support the routine use of CT arthrography elbow for nerve abnormalities at the elbow following radiographs. CT Elbow CT axial images in flexion and extension can demonstrate recurrent ulnar nerve dislocation because of a snapping of the medial head of the triceps [47]. MR Arthrography Elbow There is limited evidence to support the routine use of MR arthrography elbow for nerve abnormalities following radiographs. MRI Elbow T2-weighted MR neurography is the reference standard for imaging ulnar nerve entrapment (UNE) [48-50]. Most common findings include high signal intensity and nerve enlargement [50]. Diagnostic confidence can be increased with the use of diffusion-tensor imaging [49,51]. Diffusion-tensor imaging and tractography also provide quantitative information in 3-D perspective [47,49]. However, 3T MRI has only fair-to-moderate agreement for localization of compression points in UNE [52,53]. Radial nerve, median nerve, and other entrapment syndromes can also be evaluated with MRI [54,55]. US Elbow US elbow is another option for evaluation of UNE. Assessment of cross-sectional area/nerve thickness has high accuracy rates [48,56-58]. US also accurately demonstrates hourglass constriction of the nerve [59]. Dynamic US is helpful in demonstrating nerve dislocation in ulnar nerve neuropathy and snapping triceps syndrome [59-62]. Shear-wave elastography is a newer method used for the diagnosis of ulnar neuropathy at the elbow. Values of 100% specificity, sensitivity, and both positive and negative predictive value have been reported [63,64]. Chronic Elbow Pain Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www. acr.org/ac.


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction.  Introduction/Background Small-bowel obstruction (SBO) is responsible for up to 16% of hospital admissions for abdominal pain with mortality ranging between 2% to 8% overall, and as high as 25% when associated with bowel ischemia [1,2]. Radiologic imaging plays the key role in the diagnosis and management of SBO because neither patient presentation, the clinical examination, nor laboratory testing are sufficiently sensitive or specific enough to diagnose or guide management [2-8]. Imaging not only diagnoses the presence of SBO but also can aid in the differentiation of high-grade from low-grade obstruction. This differentiation helps to guide referring physicians between surgical treatment for high-grade or complicated SBO versus conservative management with enteric tube decompression. Imaging also serves to localize the site of obstruction and evaluate possible causes of obstruction with the most common cause being adhesions, accounting for 70% of all cases. Other causes include hernias, malignancies, Crohn disease, intussusception, volvulus, gallstone ileus, obstructive foreign bodies and bezoars, trauma, endometriosis, and iatrogenic causes. Finally, imaging can play a role in the detection of related findings that may prompt surgical treatment such as ischemia, internal hernia, or volvulus [2-8]. This document refers to imaging appropriateness in diagnosis of adult patients, >18 years of age. Discussion of Procedures by Variant Variant 1: Suspected small-bowel obstruction. Acute presentation. Initial imaging. The typical acute presentation of a patient suspected of having SBO includes intermittent crampy central abdominal pain, distension, nausea, and vomiting. Physical examination findings include abdominal distension with either absent or high-pitched bowel sounds. Abnormal laboratory findings such as an elevated white blood cell count, elevated lactic acid, or elevated serum amylase raise the suspicion for a complication such as ischemia.


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. Most cases of SBO are low grade and may be treated conservatively with enteric tube decompression, intravenous (IV) fluids, aBoston University Medical Center, Boston, Massachusetts. bDuke University Medical Center, Durham, North Carolina. cPanel Chair, University of Wisconsin Hospital & Clinics, Madison, Wisconsin. dPanel Vice-Chair, University of California San Diego, San Diego, California. eThe University of South Florida Morsani College of Medicine, Tampa, Florida. fUniversity of Texas Health Science Center at Houston and McGovern Medical School, Houston, Texas; American Gastroenterological Association. gVirginia Tech Carilion School of Medicine, Roanoke, Virginia. hUniversity of Colorado School of Medicine Anschutz Medical Campus, Aurora, Colorado; American College of Emergency Physicians. iMassachusetts General Hospital, Boston, Massachusetts. jMedstar Georgetown University Hospital, Washington, District of Columbia. kCleveland Clinic, Cleveland, Ohio. lEmory University, Atlanta, Georgia. mPenn State Health, Hershey, Pennsylvania. nUniversity of Alabama at Birmingham, Birmingham, Alabama. oDartmouth-Hitchcock Medical Center, Lebanon, New Hampshire. pUniversity of California San Francisco, San Francisco, California. qSpecialty Chair, Virginia Commonwealth University Medical Center, Richmond, Virginia. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Suspected Small-Bowel Obstruction pain medication, and sometimes antibiotics.


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. However, imaging and laboratory findings that suggest a higher grade SBO with a complication, such as ischemia, closed-loop obstruction, volvulus, or complete obstruction, may prompt more urgent surgical treatment. Patients with high-grade SBO may present with more severe abdominal pain, as well as a higher risk of bowel ischemia and perforation. However, physical examination and laboratory tests are neither sufficiently sensitive nor specific to determine which patients with SBO have coexistent strangulation or ischemia. Early imaging diagnosis and intervention is therefore critical for successful treatment and minimization of mortality, which can be as high as 25% in the setting of ischemia. The goals of imaging in high-grade SBO are to evaluate the severity of the obstruction, identify the etiology/site of the obstruction, and to detect the presence of complications, such as volvulus, strangulation, closed-loop obstruction, and ischemia. Specific imaging signs that suggest ischemia include abnormally decreased or increased bowel wall enhancement, intramural hyperdensity on noncontrast CT, bowel wall thickening, mesenteric edema, ascites, and pneumatosis or mesenteric venous gas. The presence of ischemia warrants immediate surgery. CT Abdomen and Pelvis Multiple publications have confirmed the use and accuracy of a standard abdominal and pelvic CT examination in patients with a suspected high-grade SBO. A diagnostic accuracy of more than 90% has been reported [4,5,17], with high accuracy for distinguishing SBO from an adynamic small-bowel ileus [6], and for identifying the cause of obstruction [17-20]. Patients with a suspected high-grade obstruction do not require any oral contrast medium because the nonopacified fluid in the bowel provides adequate intrinsic contrast.


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. Additionally, oral contrast use in a known or suspected high-grade SBO does not add to diagnostic accuracy and can delay diagnosis, increase patient discomfort, and increase the risk of complications, particularly vomiting and aspiration. The use of positive oral contrast agents can also potentially limit the ability to detect abnormal bowel wall enhancement in the case of ischemia and hypoperfusion. However, SBO may be identified in patients who have undergone CT with oral (with or without IV) contrast (ie, when SBO was not specifically suspected at the time the study was ordered/protocolled). Multidetector CT scanners with multiplanar reconstruction capabilities have been noticeably more effective for evaluating SBO and other abdominal pathology [21-26]. Multiplanar reformations have also been found to increase accuracy and confidence in locating the transition zone in SBO, which can be a useful adjunct if an operative intervention is planned [24,27,28]. CT with IV contrast is preferable for routine imaging of suspected SBO, in part to demonstrate whether the bowel is perfusing normally or is potentially ischemic, and in a minority of cases, to provide information about the potential etiology, such as Crohn disease and neoplasm. Noncontrast CT appears to have comparable accuracy for diagnosing or excluding high-grade SBO, although determination for ischemia is reduced [29]. CT Enteroclysis In the clinical setting of acute pain and distention, the use of CT enteroclysis is not favorable, because patients cannot tolerate the active infusion of oral contrast into an obstructed small-bowel. CT enteroclysis is generally favored over conventional enteroclysis because it avoids the problem of overlapping small-bowel loops, and it has been shown to demonstrate a larger number of bowel abnormalities and more abnormalities outside the bowel [61].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. Suspected Small-Bowel Obstruction To our knowledge; however, CT enteroclysis is not widely used in the United States at present, especially for acute presentations of bowel obstruction. CT Enterography CT enterography does not require intubation of the small-bowel but instead relies on large volumes of orally ingested contrast in a set time interval. In the setting of suspected obstruction of this clinical scenario, patients cannot generally tolerate the oral contrast administration requirements. As in the case of CT enteroclysis, the use in the acute patient presentation is not favorable because of a lack of tolerance to ingest a relatively large volume of fluid if the bowel is obstructed. Fluoroscopy Small Bowel Enteroclysis There is solid evidence that enteroclysis is highly reliable in revealing sites of low- and high-grade SBO [62,63], as well as for distinguishing adhesions from obstructing neoplasms or other etiologies [62]. Despite this evidence, enteroclysis is not useful in the acute situation of suspected obstruction in which the patient is ill. In this clinical scenario, such patients cannot tolerate the invasive nature of the examination. Fluoroscopy Small Bowel Follow-Through Opinions remain divided on the usefulness of SBFT examinations with an orally administered barium contrast or water-soluble contrast. Some investigators have found this examination useful for managing suspected SBO in 68% to 100% of cases [64]. However, the ability to diagnose ischemic loops or bowel perforation can be limited. SBFT does not typically evaluate for other etiologies of abdominal pain that may be detected on CT. As such, the SBFT could be considered a problem-solving examination following an equivocal CT, particularly with suspected low- grade or intermittent or partial obstruction [65]. Early reports of possible therapeutic benefits of the use of water- soluble contrast agents in patients with postoperative SBO remain controversial and uncertain [14-16].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. MR Enteroclysis MR enteroclysis is not useful in the acute situation of suspected obstruction in which the patient is ill. In this clinical scenario, such patients cannot tolerate the invasive nature of the examination. MR enteroclysis appears to compare favorably with CT enteroclysis in evaluating a low-grade obstruction [66], although neither MR enteroclysis nor CT enteroclysis are in wide use because patients are often unable to tolerate the degree of small-bowel distension necessary. Children, and particularly pregnant patients, with known or suspected SBO, as well as younger patients with repetitive episodes of obstruction, are the ideal population to undergo MRI. In pregnant patients, only noncontrast sequences are obtained. In other patients, MR enteroclysis can be performed either as an IV contrast enhanced study or a noncontrast study. MR Enterography In the setting of suspected obstruction of this clinical scenario, patients cannot generally tolerate the oral contrast administration requirements related to the enterography technique. To our knowledge; however, little data are available on comparing MR enterography with other imaging examinations in patients with a suspected SBO. MRI Abdomen and Pelvis Increasing evidence supports the role of MRI for detecting and characterizing SBO. Because of absent evidence of any incremental diagnostic gain, compared with CT, MRI should not be used routinely to evaluate suspected high- grade SBO [67]. However, there may be situations in which MRI could be an appropriate alternative to CT, particularly for those who have had multiple prior CT examinations or are expected to get multiple future imaging examinations. Examinations may be difficult to interpret related to patient pain and discomfort and associated patient motion in the acute setting. Radiography Abdomen and Pelvis Abdominal radiography has been the traditional starting point for the imaging evaluation of suspected SBO [68].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. However, studies testing the use of abdominal radiographs have yielded disparate results [4,5,18,69]. Although some investigators have reported an 80% to 90% success rate in diagnosing SBO using radiographs [5], an overall accuracy somewhat approaching that of CT [7], others have achieved rates only in the 30% to 70% range [4,7,18]. In other studies, abdominal radiographs proved to be of little or no help in assessing the site or cause of SBO [70,71] and were even misleading in 20% to 40% of patients [18]. A relatively recent study; however, found that abdominal radiographs were accurate for detecting acute SBO. It should be stressed; however, that it may be difficult to differentiate an SBO from a postoperative ileus in the perioperative period based on a single examination. Serial examinations showing persistent dilated small-bowel loops with air-fluid levels and relative or complete paucity of gas in the colon favor SBO. Suspected Small-Bowel Obstruction Despite the relatively high accuracy of abdominal radiographs in detecting SBO, CT provides much more information, including the site and cause of the obstruction and complications of SBO. As a result, CT findings generally influence patient management much more than do abdominal radiographs. In light of these inconsistent results, it is reasonable to expect that abdominal radiographs will not be definitive in many patients with a suspected SBO. Radiographs could prolong the evaluation period. Therefore, in patients with a known or suspected SBO, fluoroscopic-contrast examinations (SBFT, conventional enteroclysis), and particularly, cross-sectional imaging examinations (CT, MRI, ultrasound [US]), as well as specialized cross-sectional imaging examinations (CT enterography, CT enteroclysis, MR enterography, and MR enteroclysis), may be more useful options for diagnosis. Variant 2: Suspected intermittent or low-grade small-bowel obstruction. Indolent presentation.


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. Patients with suspected intermittent or low-grade SBO may have a more indolent presentation in which the patient may be asymptomatic at baseline with intermittent symptoms. If a SBO is present, it may be intermittent or very low-grade, requiring provocative measures such as bowel distention to visualize this process on a consistent basis. In low-grade SBO, there is sufficient luminal patency to allow contrast to flow beyond the point of obstruction. Low-grade or intermittent SBO can therefore be more difficult to diagnose with modalities that do not maximally distend or exaggerate the caliber of the small-bowel lumen. The patient may be relatively asymptomatic and with a more nonspecific presentation with other differential considerations possible. On imaging, it may be difficult to visualize dilated abnormal loops and a transition point. In these cases, volume-challenge or dynamic enteral examinations may be preferred to accentuate mild or subclinical obstructions and to better challenge the distensibility of small-bowel. The multiplanar reformatting capabilities of multidetector CT scanners has also helped in evaluating these patients. CT Abdomen and Pelvis Although standard abdominal and pelvic CT examinations in patients with a suspected high-grade SBO have shown diagnostic accuracies of greater than 90% [4,5,17], low-grade or intermittent obstruction has been less accurately diagnosed with a sensitivity of only 48% to 50% and a specificity of 94% [7,80]. In this situation of suspected intermittent or low-grade SBO, the bowel loops may look unremarkable with intrinsic enteral fluid or standard oral contrast administration at CT. Oral contrast may be purposefully given to these patients when SBO is a consideration. When a transition point is identified without passage of orally administered positive contrast, optional re-imaging within 24 hours may depict passage of oral contrast beyond the transition point, indicating incomplete or partial obstruction [81].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. When a transition point is not identified, optimized distention of the bowel (through either CT enteroclysis or CT enterography) may be needed to make an intermittent or mild obstruction apparent. CT Enteroclysis CT enteroclysis offers improved sensitivity and specificity over standard CT examinations in evaluating suspected intermittent or low-grade SBO [68,82-84]. The placement of a nasoduodenal tube with active controlled infusion of oral contrast optimizes detection of subtle causes of mild obstructions. There is solid evidence that enteroclysis is highly reliable in revealing sites of low-grade SBO [62,63,85], as well as for distinguishing adhesions from obstructing neoplasms or other etiologies [62]. CT enteroclysis is generally favored over conventional enteroclysis because it avoids the problem of overlapping small-bowel loops; it also has been shown to demonstrate a larger number of bowel abnormalities and more abnormalities outside the bowel [61]. CT enteroclysis should be considered, especially for patients who have a history of malignancy [68]. To our knowledge; however, CT enteroclysis is not widely used in the United States at present because of the practical challenges of nasojejunal intubation and the often-associated issues related to conscious sedation and continuous patient monitoring. Suspected Small-Bowel Obstruction CT Enterography CT enterography does not require intubation of the small-bowel and, therefore, has greater patient acceptance [86]. The increased distention of small-bowel related to the oral contrast ingestion protocol optimizes detection of bowel pathology. To our knowledge; however, its clinical usefulness for diagnosing intermittent or low-grade SBO has not been convincingly established, although one small series showed promise [87].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. Although there is little evidence that CT enterography can be used reliably to identify intermittent- or low-grade SBO, the bowel is typically distended to a greater degree than with standard CT and potentially may be of benefit if CT enteroclysis is not performed at an institution. Fluoroscopy Small-Bowel Enteroclysis Methods of examination that challenge the distensibility of the small-bowel, including conventional (ie, fluoroscopic) enteroclysis and CT enteroclysis, offer improved sensitivity and specificity over standard barium small-bowel and CT examinations in evaluating suspected intermittent or low-grade SBO [18,68,82-84,88]. There is solid evidence that enteroclysis is highly reliable in revealing sites of low-grade SBO [62,63], as well as for distinguishing adhesions from obstructing neoplasms or other etiologies [62]. However, enteroclysis has low patient acceptance. Fluoroscopy Small-Bowel Follow-Through Opinions remain divided on the usefulness of SBFT examinations with an orally administered barium contrast. Some investigators have found this examination useful for managing suspected SBO in 68% to 100% of cases [64]. The SBFT could be considered a problem-solving examination following an equivocal CT, particularly with low- grade or intermittent or partial obstruction [65]. Because SBFT is limited by nonuniform small-bowel filling, it cannot test distensibility and has limitations posed by intermittent fluoroscopy; some authorities argue that enteroclysis is the more appropriate imaging examination in problematic SBO cases, especially in low-grade or intermittent obstruction [62,89]. Early reports of possible therapeutic benefits of the use of water-soluble contrast agents in patients with postoperative SBO remain controversial and uncertain [14-16].


Suspected Small Bowel Obstruction

Suspected Small Bowel Obstruction. MR Enteroclysis MR enteroclysis appears to compare favorably with CT enteroclysis in evaluating a low-grade obstruction [66], although neither MR enteroclysis nor CT enteroclysis are in wide use because patients are often unable to tolerate the degree of small-bowel distension necessary. The ability of MR enteroclysis to monitor small-bowel filling in real-time without the use of ionizing radiation is an advantage over fluoroscopic and CT enteroclysis. Children and, particularly, pregnant patients with known or suspected SBO, as well as younger patients with repetitive episodes of obstruction, are the ideal population to undergo MRI. In pregnant patients, only noncontrast sequences are obtained. In other patients, MR enteroclysis can be performed either as an IV-contrast enhanced study or a noncontrast study. MR Enterography MR enterography may be superior to routine MRI examinations and is better accepted by patients than MR enteroclysis. To our knowledge; however, little data are available on comparing MR enterography with other imaging examinations in patients with a suspected SBO. MRI Abdomen and Pelvis Increasing evidence supports the role of MRI for detecting and characterizing SBO. The use of fast multiplanar pulse sequences such as half-Fourier acquisition single-shot turbo spin-echo and balanced gradient-echo sequences allow for functional assessment of the distensibility of strictures. Without optimized bowel preparation, bowel loops at MR with standard protocol (ie, without bowel distension) may be unremarkable at intermittent or low-grade obstructions. Radiography Abdomen and Pelvis Abdominal radiography has been the traditional starting point for the imaging evaluation of suspected SBO [68]. However, studies testing the use of abdominal radiographs have yielded disparate results [4,5,18,69].


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome.  Introduction/Background Acute aortic syndrome (AAS) includes the entities of acute aortic dissection (AD), intramural hematoma (IMH), and penetrating atherosclerotic ulcer (PAU). AAS typically presents with sudden onset of severe, tearing, anterior, or interscapular back pain [1]. Symptoms may be dominated by malperfusion syndrome due to obstruction of the lumen of the aorta and/or a side branch when the intimal and medial layers are separated. Risk factors include hypertension, family history, and underlying collagen vascular disorders [2]. Timely diagnosis of AAS is crucial to permit prompt management; early mortality rates are reported to be 1% to 2% per hour after the onset of symptoms for untreated ascending AD [3]. Medical management of acute ascending AD is associated with a mortality rate of nearly 20% by 24 hours after presentation, 30% by 48 hours, 40% to 70% by day 7 [4], and 50% by 1 month [3,5]. The major cause of early death with AAS is aortic rupture [6]. AAS limited to the descending aorta may be managed medically and/or with open surgical or endovascular treatment based on extent of disease, aortic size, malperfusion of end organs, and clinical parameters; medical management is usually undertaken unless the aorta is dilated and/or there is mesenteric or limb ischemia [6]. IMH occurs with approximately 10% of the frequency of AD [7], and can be seen in isolation or in conjunction with AD and PAU. Imaging findings of AAS include any disruption of the intimal and medial layers, either with an IMH within the media (with or without the presence of a penetrating ulcer) or with an intimal flap. The prevalence of isolated IMHs in patients with suspected AAS is reported to be 21% to 30% [3]. Over time, 28% to 47% of patients may progress to a classic AD, and in other patients, the IMH will resolve with or without aneurysmal enlargement of the aorta [6]. PAUs that disrupt the intima most commonly occur in the mid and distal descending aorta [8].


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. Classification of Acute Aortic Syndrome Classification of AAS is based on identifying the location of the most proximal location of the intimal flap and/or IMH. In DeBakey classification type I and type II ADs, the proximal intimal tear is located in the ascending aorta, usually just a few centimeters above the aortic valve. In type I dissection, the intimal flap extends for a variable distance beyond the aortic arch and usually into the descending aorta, whereas in type II the intimal flap is confined to the ascending aorta. DeBakey type III dissection originates in the descending aorta, usually just beyond the origin aUniversity of Washington, Seattle, Washington. bPanel Chair, Duke University Medical Center, Durham, North Carolina. cPanel Vice-Chair, Massachusetts General Hospital, Boston, Massachusetts. dUniversity of Louisville School of Medicine, Louisville, Kentucky. eUniversity of Michigan Health System, Ann Arbor, Michigan. fThe University of Chicago Medical Center, Chicago, Illinois; American College of Physicians. gKaiser Permanente, Los Angeles, California. hVancouver General Hospital, Vancouver, British Columbia, Canada. iUniversity of California San Diego, San Diego, California. jHarvard Medical School, Boston, Massachusetts. kSentara Norfolk General/Eastern Virginia Medical School, Norfolk, Virginia; American College of Emergency Physicians. lNaval Medical Center Portsmouth, Portsmouth, Virginia. mMassachusetts General Hospital, Boston, Massachusetts. nOhio State University, Nationwide Children's Hospital, Columbus, Ohio; Society for Cardiovascular Magnetic Resonance. oUniversity of Virginia Health Center, Charlottesville, Virginia; Society of Cardiovascular Computed Tomography. pAscension Healthcare Wisconsin, Milwaukee, Wisconsin; Nuclear cardiology expert. qSpecialty Chair, UT Southwestern Medical Center, Dallas, Texas.


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Suspected Acute Aortic Syndrome of the left subclavian artery, and propagates antegrade along the descending aorta. Rarely, the proximal intimal tear occurs in an unusual location, such as the abdominal aorta [6]. Stanford type A dissection refers to any dissection involving the ascending aorta and therefore is equivalent to DeBakey type I and type II. Stanford type B dissection is any AD that does not involve the ascending aorta, including dissections that originate in the aortic arch. Stanford type B dissection is therefore equivalent to DeBakey type III [10]. Both the DeBakey and Stanford classifications are ambiguous in regard to AD starting on the aortic arch. Such lesions may be best described as Stanford type B with arch involvement [6,11]. All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and reconstructions/reformats. Only in CTA, however, is 3-D rendering a required element. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes. Discussion of Procedures by Variant Variant 1: Acute chest pain; suspected acute aortic syndrome Aortography Chest Historically, conventional angiography was considered the reference standard for diagnosing AAS with sensitivity, specificity, positive predictive value, and negative predictive value of 88%, 94%, 96%, and 84%, respectively, reported for identification of an intimal flap [13].


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. The diagnostic accuracy of digital subtraction angiography approaches 98% in some series for identification of an AD. Angiography permits management of patients who are critically ill and can also assess aortic regurgitation and aortic branch vessel involvement (including the coronary arteries) [14]. High frame rates facilitate identification of the intimal tear and the degree of aortic insufficiency. False-negative arteriograms may occur when the false lumen is not opacified, when there is simultaneous opacification of the true and false lumen, and when the intimal flap is not displayed in profile. Disadvantages of angiography include the fact that it is invasive, requires iodinated contrast material, and that it has a limited ability to assess the surrounding structures (eg, presence of mediastinal hemorrhage), which is readily detected by other cross-sectional imaging modalities [1,3]. CT Chest Without IV Contrast CT chest without intravenous (IV) contrast cannot assess the lumen of that aorta, but AAS can be inferred by identifying displaced aortic calcifications or IMHs, findings that are shown to be 94% and 71% sensitive for diagnosing AAS when using contrast-enhanced CTA as the reference standard [15]. Another study found that abnormal aortic wall contour and paraaortic hematoma were also predictive of AAS. These imaging findings were incorporated into a decision-rule that predicted the presence of AAS with a mean sensitivity of 93% [16]. However, few patients in the derivation data set had PAU as a diagnosis, and the number of patients with AAS in the validation data set was not reported. CT without IV contrast can identify complications from AAS, such as mediastinal, pericardial, and/or pleural hematoma. CT Chest With IV Contrast CT chest with IV contrast can identify the presence of an AAS and the presence of complications such as mediastinal, pericardial, and/or pleural hematoma.


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. There is no relevant literature that compares the diagnostic accuracy of CT chest with IV contrast (delayed-phase enhancement) versus CTA chest (arterial-phase contrast). Suspected Acute Aortic Syndrome Dual-energy multidetector CT enables generation of CT chest images without and with IV contrast enhancement by producing virtual unenhanced imaging studies. However, the use of these virtual unenhanced images in place of true unenhanced images remains controversial [18-20]. CTA Coronary Arteries There is no relevant literature supporting the use of CTA of the coronary arteries for the diagnosis of AAS. CTA of coronary arteries may be used in patients with known AD for which coronary arterial disease classification is needed prior to open surgical repair for an AD involving the ascending aorta. This document includes the triple-rule-out (TRO) protocol under the topic of CTA of coronary arteries as the TRO includes simultaneous assessment of the pulmonary arteries, aorta, and coronary arteries. CTA Chest With IV Contrast CTA can demonstrate the presence of aortic intimal flaps, branch vessel involvement, and entry and reentry sites, as well as identification of penetrating ulcers. The addition of a noncontrast acquisition as part of the CTA examination can be used to confirm the presence of an IMH. CTA chest can also allow for simultaneous assessment of adjacent mediastinal, pericardial, and pleural spaces. CTA chest was the most common initial diagnostic test performed in patients enrolled in the International Registry of Acute Aortic Dissection, and is being used with increasing frequency [21]. CTA was used to diagnose AD with 82% sensitivity and 100% specificity [22]. Numerous prior studies evaluating the accuracy of CT use in diagnosing AD have demonstrated sensitivities of 90% to 100% but lower specificities ranging from 87% to 100% [23-26]. However, these studies evaluated conventional CT, which has largely been supplanted by faster multidetector CT.


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. One multidetector CT study enrolling 57 patients has reported sensitivities and specificities of 100% [22]. CT findings may also be used to predict patient outcome. For example, in one retrospective study of 83 patients with type B dissections, the morphologic features of a dissection were associated with an increase in late adverse events [27]. CTA with IV contrast also enables detection of focal intimal disruptions or also ulcer-like projections as prognostic indicators in IMH. In one study of 107 patients, aorta-related death or need for invasive surgery was increased when focal intimal disruptions or ulcer-like projections were present (hazard ratio, 24.43) [29]. CTA with IV contrast can be used to diagnose penetrating PAU, but contrast does not enable additional prognostic imaging findings. PAU prognosis has been associated with the presence or absence of aortic rupture, but in one study, aortic diameter, ulcer size, or the presence of IMH did not affect prognosis [30]. Compared with CTA chest, TRO CT protocols can be used to assess for additional, potentially fatal possibilities such as pulmonary embolism and acute coronary syndrome [31,32]. It has been reported that TRO CT can safely eliminate further diagnostic testing in >75% of patients in the appropriate patient population performed specifically for assessing AD [33]. CTA Chest, Abdomen, and Pelvis With IV Contrast CTA of the chest, abdomen, and pelvis allows for imaging of both the thoracic and abdominal aorta, and it provides assessment of extension of the dissection along the thoracic, abdominal, and pelvic branch vessels with one injection of IV contrast and a single breath-hold acquisition. Postprocessing of the volumetric data set, using multiplanar reformatting and 3-D volume rendering, facilitates evaluation of the location and course of the intimal flap [34], branch vessel, and visceral organ involvement.


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. A meta-analysis of 3 studies examining CTA for the diagnosis of dissection showed a pooled sensitivity of 100% and a specificity of 98% [21]. When CTA is used as a first-line test, the International Registry of Acute Aortic Dissection reported a sensitivity of 93% for diagnosing dissection [35]. Suspected Acute Aortic Syndrome MRA Chest Without IV Contrast There is no relevant literature supporting the use of MR angiography (MRA) chest without IV contrast for the diagnosis of AAS. Several studies report noncontrast MRA techniques and compare them with contrast-enhanced techniques, but studies were neither blinded to the reference standard or nor did they contain control subjects [36,37]. MRA Chest, Abdomen, and Pelvis Without IV Contrast There is no relevant literature supporting the use of MRA chest, abdomen, and pelvis without IV contrast for the diagnosis of AAS. Although no literature directly examines the accuracy of diagnosing AAS with MRA chest, abdomen, and pelvis without IV contrast, the accuracy for identification of an AD in the chest is similar to that of an isolated MRA chest without IV contrast with the addition of MRA abdominal and pelvic assessment. MRA Chest, Abdomen, and Pelvis Without and With IV Contrast There is no relevant literature supporting the use of MRA chest, abdomen, and pelvis without and with IV contrast for the diagnosis of AAS. Although no literature directly examines the accuracy of diagnosing AAS with MRA chest, abdomen, and pelvis without IV contrast, the accuracy for identification of an AD in the chest is similar to that of an isolated MRA chest without IV contrast with the addition of MRA abdominal and pelvic assessment. MRI Chest, Abdomen, and Pelvis Without IV Contrast There is no relevant literature supporting the use of MRI chest, abdomen, and pelvis without IV contrast for the diagnosis of AAS.


Suspected Acute Aortic Syndrome

Suspected Acute Aortic Syndrome. In contrast to MRA, MRI does not contain sequences designed to specifically produce images of the aorta, such as gating, 3-D data sets, thin sections, or double-oblique planes. MRI contains sequences that produce images in orthogonal planes, with greater slice thickness. MRI Chest, Abdomen, and Pelvis Without and With IV Contrast There is no relevant literature supporting the use of MRI chest, abdomen, and pelvis without and with IV contrast for the diagnosis of AAS. In contrast to MRA, MRI does not contain sequences designed to specifically produce images of the aorta, such as gating, 3-D data sets, thin sections, or double-oblique planes. MRI contains sequences that produce images in orthogonal planes, with greater slice thickness. Radiography Chest Chest radiographs can identify an enlarged aorta and or mediastinum and can identify complications such as pleural fluid. A substantial portion of patients with AAS may have a normal chest radiograph, and further imaging should be pursued despite a normal chest radiograph in cases of suspected AAS. In most cases when patients with an AAS have an abnormal radiograph, the findings are nonspecific [41]. The most recent report from the International Registry of Acute Aortic Dissection showed that in the last 10 years, the incidence of abnormal radiographic findings has decreased in patients with AD [10]. In that report, radiographs were reported as abnormal in 52% of patients with type A AD, whereas previously it was 61%. Abnormal findings were present in 39% of patients with type B AD, whereas previously it was 56%. Radiographs were reported to be completely normal in 36% to 38% of patients with AD. In another study that measured the diagnostic performance of radiography for all diagnoses of AAS, including IMH, PAU, and ruptured aneurysm, chest radiography had a sensitivity of 70.8% and a specificity of 82.5% [42].


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization.  Estimates of the prevalence of claudication in the general population range from 1.6% to almost 8%, depending on age, sex, the geographic location of the population, and the diagnostic criteria used [2,3]. In most studies, fewer than 10% of patients with intermittent claudication progress to chronic limb-threatening ischemia in 5 years [4,5]. However, one large meta-analysis of 16,440 patients demonstrated that 21% of patients with intermittent claudication progressed to chronic limb-threatening ischemia [6]. The presence of vascular disease in patients with symptoms of claudication is reliably established by a variety of noninvasive hemodynamic tests. In the absence of demonstrable arterial disease, imaging studies of other systems, such as the lumbar spine or soft tissues of the pelvis, may be indicated. If peripheral vascular disease is confirmed, additional studies may be indicated to screen the heart and carotid arteries for involvement [2]. Initial Imaging Definition Initial imaging is defined as imaging at the beginning of the care episode for the medical condition defined by the variant. More than one procedure can be considered usually appropriate in the initial imaging evaluation when: The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org OR Special Imaging Considerations CT angiography (CTA) in the tibial arteries is limited by the difficulty in accurately timing the image acquisition with respect to arrival of the iodine bolus: images acquired too late will have problematic venous contamination; images acquired too early will not have adequate contrast enhancement.


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. More common with newer CT technologies is imaging too early either for one leg with slow flow from outflow disease or for both legs secondary to the very fast scanning protocols. Delayed images of the calves can be obtained to catch the bolus in these patients. The presence of diffusely diseased arteries can present challenges during angiography, because stenosis severity can be difficult to determine in the absence of normal arterial segments for comparison. In addition, serial lesions, luminal irregularity, and the degree of collateral development may produce effects on the blood flow that are difficult to quantify angiographically. The main drawbacks of arteriography in patients with claudication are its invasive nature and the known complications from catheterization [2,10]. These difficulties can be avoided by using examinations such as duplex ultrasound (US), MR angiography (MRA), or CTA to accurately triage patients with confirmed PAD for percutaneous or surgical treatments. For the latter, preoperative arteriography may not be needed. Finally, arteriography has inconsistent correlation between the hemodynamic or functional effects and the morphology of the arterial lesions [12]. Several studies have reported this problem, but in some of them the problem may be accentuated by less-than-optimal angiographic technique (eg, single-projection, nonselective injections). CTA Abdomen and Pelvis with Bilateral Lower Extremity Runoff With IV Contrast CTA is commonly used for imaging peripheral vascular disease. Multidetector CT scanners, including helical and multistation axial acquisitions, enable rapid scanning of the entire arterial system [13]. When compared with catheter arteriography, CTA offers volumetric as opposed to planar images. The volumetric acquisition enables extensive image postprocessing, including multiplanar reformatted and maximum-intensity projection images to create an arterial road map [13].


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. With optimized timing of the acquisition, CT images include collaterals and arteries distal to occlusions that may not appear on catheter angiography images. Like MRA, CTA is a cross-sectional technique, which shows nonvascular findings, as well as vascular lesions associated with aneurysms and cystic adventitial disease that are not detected with the projectional technique of catheter arteriography. Unlike imaging of the peripheral arteries, CTA is considered to have replaced catheter angiography as the reference standard for imaging of the aorta [13,14]. CTA can readily detect stenosis caused by plaque or thrombus in the aorta and iliac arteries that may be contributing to symptoms of claudication. CTA alone can be used to plan treatment, including assessment of the length, severity, and number of stenoses [15,16]. Compared with catheter angiography, the sensitivity and specificity of CTA for detection of stenoses >50% diameter are 90% to 100% [10,17-20]. Accuracy in patients with bypass grafts is excellent compared with duplex Lower Extremity Arterial Claudication US [21]. CTA is also more clinically useful than duplex US [21]. However, heavily calcified atheromatous disease can limit the ability to interpret CT images. This drawback is usually more pronounced in tibial arteries. Identification of patients who may be unsuitable candidates for CTA of the tibial arteries (eg, >80 years of age, diabetic, on dialysis) will reduce the number of nondiagnostic studies [22]. Dual-energy CTA can reduce blooming and beam-hardening artifact created by heavily calcified atheromatous disease and metallic stents [23]. Compared with MRA, CT has the advantages of more rapid acquisition, better safety in patients with pacemakers or defibrillators, and generally less severe artifacts from metal. Finally, claustrophobia is far less of a problem.


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. CTA Abdomen and Pelvis with Bilateral Lower Extremity Runoff Without and With IV Contrast CTA is commonly used for imaging peripheral vascular disease. Multidetector CT scanners, including helical and multistation axial acquisitions, enable rapid scanning of the entire arterial system [13]. When compared with catheter arteriography, CTA offers volumetric as opposed to planar images. The volumetric acquisition enables extensive image postprocessing, including multiplanar reformatted and maximum-intensity projection images to create an arterial road map [13]. With optimized timing of the acquisition, CT images include collaterals and arteries distal to occlusions that may not appear on catheter angiography images. Like MRA, CTA is a cross-sectional technique, which shows nonvascular findings as well as vascular lesions associated with aneurysms and cystic adventitial disease that are not detected with the projectional technique of catheter arteriography. Unlike imaging of the peripheral arteries, CTA is considered to have replaced catheter angiography as the reference standard for imaging of the aorta [13,14]. CTA can readily detect stenosis caused by plaque or thrombus in the aorta and iliac arteries that may be contributing to symptoms of claudication. CTA alone can be used to plan treatment, including assessment of the length, severity, and number of stenoses [15,16]. Compared with catheter angiography, the sensitivity and specificity of CTA for detection of stenoses >50% diameter are 90% to 100% [10,17-20]. Accuracy in patients with bypass grafts is excellent compared with duplex US [21]. CTA is also more clinically useful than duplex US [21]. However, heavily calcified atheromatous disease can limit the ability to interpret CT images. This drawback is usually more pronounced in tibial arteries.


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. Identification of patients who may be unsuitable candidates for CTA of the tibial arteries (eg, >80 years of age, diabetic, on dialysis) will reduce the number of nondiagnostic studies [22]. Dual-energy CTA can reduce blooming and beam-hardening artifact created by heavily calcified atheromatous disease and metallic stents [23]. CTA without intravenous (IV) contrast can be performed before CTA with IV contrast to fine-tune the scan range and identify calcified plaque and calcium within thrombus [24]. Compared with MRA, CT has the advantages of more rapid acquisition, better safety in patients with pacemakers or defibrillators, and generally less severe artifacts from metal. Finally, claustrophobia is far less of a problem. CTA Lower Extremity With IV Contrast CTA is commonly used for imaging peripheral vascular disease. Multidetector CT scanners, including helical and multistation axial acquisitions, enable rapid scanning of the entire arterial system [13]. When compared with catheter arteriography, CTA offers volumetric as opposed to planar images. The volumetric acquisition enables extensive image postprocessing, including multiplanar reformatted and maximum-intensity projection images to create an arterial road map [13]. With optimized timing of the acquisition, CT images include collaterals and arteries distal to occlusions that may not appear on catheter angiography images. Like MRA, CTA is a cross-sectional technique, which shows nonvascular findings, as well as vascular lesions associated with aneurysms and cystic adventitial disease that are not detected with the projectional technique of catheter arteriography. CTA alone can be used to plan treatment, including assessment of the length, severity, and number of stenoses [15,16]. Compared with catheter angiography, the sensitivity and specificity of CTA for detection of stenoses >50% diameter are 90% to 100% [10,17-20].


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. Accuracy in patients with bypass grafts is excellent compared with duplex US [21]. CTA is also more clinically useful than duplex US [21]. However, heavily calcified atheromatous disease can limit the ability to interpret CT images. This drawback is usually more pronounced in tibial arteries. Identification of patients who may be unsuitable candidates for CTA of the tibial arteries (eg, >80 years of age, diabetic, on dialysis) will reduce the number of nondiagnostic studies [22]. Dual-energy CTA can reduce blooming and beam-hardening artifact created by heavily calcified atheromatous disease and metallic stents [23]. Compared with MRA, CT has the advantages of more rapid acquisition, better safety in patients with pacemakers or defibrillators, and generally less severe artifacts from metal. Finally, claustrophobia is far less of a problem. Lower Extremity Arterial Claudication CTA of one or both lower extremities can be performed without imaging the abdomen and pelvis when aortoiliac disease is not a concern or the state of the aorta and iliac arteries is already known. CTA Lower Extremity Without and With IV Contrast CTA is commonly used for imaging peripheral vascular disease. Multidetector CT scanners, including helical and multistation axial acquisitions, enable rapid scanning of the entire arterial system [13]. When compared with catheter arteriography, CTA offers volumetric as opposed to planar images. The volumetric acquisition enables extensive image postprocessing, including multiplanar reformatted and maximum-intensity projection images to create an arterial road map [13]. With optimized timing of the acquisition, CT images include collaterals and arteries distal to occlusions that may not appear on catheter angiography images.


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. Like MRA, CTA is a cross-sectional technique, which shows nonvascular findings as well as vascular lesions associated with aneurysms and cystic adventitial disease that are not detected with the projectional technique of catheter arteriography. CTA alone can be used to plan treatment, including assessment of the length, severity, and number of stenoses [15,16]. Compared with catheter angiography, the sensitivity and specificity of CTA for detection of stenoses >50% diameter are 90% to 100% [10,17-20]. Accuracy in patients with bypass grafts is excellent compared with duplex US [21]. CTA is also more clinically useful than duplex US [21]. However, heavily calcified atheromatous disease can limit the ability to interpret CT images. This drawback is usually more pronounced in tibial arteries. Identification of patients who may be unsuitable candidates for CTA of the tibial arteries (eg, >80 years of age, diabetic, on dialysis) will reduce the number of nondiagnostic studies [22]. Dual-energy CTA can reduce blooming and beam-hardening artifact created by heavily calcified atheromatous disease and metallic stents [23]. CTA without IV contrast can be performed before CTA with IV contrast to fine-tune the scan range and identify calcified plaque and calcium within thrombus [24]. Compared with MRA, CT has the advantages of more rapid acquisition, better safety in patients with pacemakers or defibrillators, and generally less severe artifacts from metal. Finally, claustrophobia is far less of a problem. CTA of one or both lower extremities can be performed without imaging the abdomen and pelvis when aortoiliac disease is not a concern or the state of the aorta and iliac arteries is already known. MRA Abdomen and Pelvis with Bilateral Lower Extremity Runoff With IV Contrast Contrast-enhanced MRA (CE-MRA) techniques continue to evolve and improve.


Lower Extremity Arterial Claudication Imaging Assessment for Revascularization. Three-dimensional imaging, contrast enhancement with gadolinium, subtraction, cardiac gating, bolus chase, parallel imaging, optimized K- space filling, 3T magnet strength, and improved coil technology have led to improved temporal resolution, spatial resolution, and signal-to-noise ratio in CE-MRA. Its sensitivity and specificity for detection of stenoses >50% are now in the 90% to 100% range [25-27]. Unlike with CTA, the presence of calcium in small vessels does not result in a CE-MRA artifact [28]. Furthermore, dedicated time-resolved CE-MRA of the tibial and pedal arteries significantly increases diagnostic accuracy of tibial and pedal lesions compared with standard multistation CE- MRA. Time-resolved CE-MRA also reduces insufficient arterial filling and venous contamination, which are common limitations of standard multistation CE-MRA [28]. Although CE-MRA has not supplanted angiography as a reference standard, one small study demonstrated that 3T CE-MRA with calf compression (to prevent venous contamination) resulted in better visualization of tibial arteries than DSA [29]. For these reasons, CE-MRA is ideally suited for patients at high risk for calcification of the tibial and pedal arteries, particularly patients with diabetes and patients >80 years of age [28,30]. In comparison with duplex US, CE-MRA is more accurate for detecting and quantifying significant stenoses and for preoperative planning [31]. In a randomized controlled trial comparison with duplex US, CE-MRA for the initial imaging workup of patients with PAD reduced the need for additional imaging [32]. In a meta-analysis comparison with CTA, CE-MRA had equivalent sensitivity and specificity for detecting arterial lesions from the aorta to the tibial arteries in patients with intermittent claudication [26]. Some technical problems limit the utility of CE-MRA for imaging PAD.