Anorectal Disease

Anorectal Disease. In 13 enemas performed by Giordano et al [36], the overall sensitivity was 7.7% for all fistula and 9% for those that involved the colon only. In a previous series of sigmoid vaginal fistulae, contrast enema detected the fistulae in 34% of cases [37]. For fistula to the urinary tract, Amendola et al compared contrast enema and cystography, which showed 50% and 30% of fistula, respectively, in 28 patients with surgically proven colovesicular fistula [38]. Fluoroscopy Cystography The data on diagnosis of rectovesicular fistula by cystography is limited to small series in older medical literature. In series of 30 patients with enterovesicular fistula, Hsieh et al [39] reported 90% were detected by cystography and 75% by contrast enema. Fluoroscopy Vaginography Fluoroscopic vaginography is performed after obtaining anterolateral and lateral scout radiographs or spot films. A large-gauge Foley catheter, such as a 26-guage with a 30-mL balloon, is placed in the vaginal lumen. The balloon is inflated to prevent the spillage of contrast material out of the vagina. Water-soluble contrast is injected under fluoroscopic guidance, and spot radiographs are obtained in the anteroposterior, right and left, oblique, and lateral views. Water-soluble contrast is preferred over barium because the endometrial cavity may fill in normal patients, and contrast may thus spill into the peritoneal cavity. Vaginography may also be performed with CT [40]. An unenhanced scan is obtained prior to vaginal opacification. The vagina is opacified in the same manner as in Anorectal Disease fluoroscopy; however, the water-soluble contrast is diluted with sterile water or normal saline (1/10, V/V) [40]. A second CT is obtained after vaginal filling. It may be acquired with or without IV contrast, depending upon the clinical indication. Giordano et al [36] reported a sensitivity of 79% and PPV of 100% for fluoroscopic vaginography for identification of fistulous tracts in 27 patients with suspected fistulae.


Anorectal Disease

Anorectal Disease. Earlier series in a smaller number of patients reported sensitivities of 100% [41,42]. Limitations of vaginography include occlusion of low fistula by the Foley catheter balloon and completely filling complex fistulous tracts that may have several branches. The high sensitivity and PPV supports the use of this procedure in certain clinical scenarios. MRI Pelvis Rectovaginal and anovaginal fistula may be visualized on MRI performed with a phased array body coil, but to our knowledge, there are no published studies reporting the accuracy of fistula detection. As such, the advantages of scanning with or without IV contrast have not been studied. Based on our knowledge of anorectal fistula, there is a clear advantage to using IV contrast to visualize collapsed tracts that do not contain fluid and would be difficult to see on T2-weighted sequences. MRI pelvis without IV contrast may be helpful in certain clinical situations but is not as good as one performed with IV contrast. Stoker et al [43] compared endoluminal coil MRI with and without IV contrast to endoluminal US, reporting a PPV for detection of fistula tracts of 92% and 100%, respectively. Radiography Pelvis Radiography is not useful in this clinical scenario because it cannot assess the presence or absence of an abscess or fistula tract. US Pelvis Transrectal Yee et al [44] reported that endoluminal US detected only 28% of rectovaginal fistula in 25 patients prior to surgical repair. However, more recent reports show improved detection; consequently, this procedure can be useful in certain clinical situations for fistula detection. In 28 patients, Yin et al [45] had a PPV of 100% for the identification of the anorectal opening of the fistula and 93% for the identification of the vaginal opening, and an overall PPV of the fistula of 90%. The limitation of endoluminal US is identification of complex fistulas with secondary branches, visualization of occluded branches, and visualization of fistula that extend beyond the field of view.


Anorectal Disease

Anorectal Disease. Variant 3: Suspected proctitis or pouchitis. Initial imaging. Proctitis, inflammation of the rectum, is a common manifestation of inflammatory bowel disease (ulcerative colitis and CD). Other causes include infections (gonorrhea, chlamydia, herpes simplex virus, HIV/acquired immunodeficiency syndrome), radiation, and ischemia. Patients present with rectal pain, discomfort, tenesmus, purulent discharge, abdominal pain, and urgency. In most patients, imaging is not required. However, if a more complex disease is clinically suspected, imaging may be indicated to define the extent of disease and/or complications. An ileal pouch anal anastomosis (IPAA), also known as a J-pouch, is the most common surgical approach for creating a continent reservoir following total proctocolectomy. This is typically performed in a two-stage procedure in patients with ulcerative colitis or familial adenomatous polyposis. Pouchitis is a common complication of IPAA, occurring in approximately 20% of patients within 1 year of surgery and 50% of patients within 10 years of surgery [46]. Pouchitis may be caused by primary infection or an immune response to an altered microbiome in the pouch lumen or mucosa. Patients may present with increased stool frequency and fluidity, tenesmus, incontinence, pain, malaise, fever, or bleeding. The symptoms of pouchitis overlap with other postoperative complications, such as dehiscence and abscess, as well as occult CD such as in patients that have presumed ulcerative colitis with undiagnosed CD or subsequently developed CD [47]. Imaging is an important complementary technique to endoscopy with biopsy to accurately diagnose and manage inflammation in the pouch. CT Enterography CT enterography techniques provide better visualization of the small bowel compared with routine CT.


Anorectal Disease

Anorectal Disease. To optimize small-bowel distention and visualization of the mucosa, patients ingest a large volume (1,000 to 2,000 cc) of neutral contrast material (such as low w/v barium solutions, water, polyethylene glycol, or methylcellulose suspensions) prior to the examination. IV contrast enhances the small-bowel wall such that it is well seen adjacent to the neutral intraluminal contrast. Single- or dual-phase (arterial and portal venous, respectively) acquisitions may be obtained. Using CT findings of inflammation (wall thickening, mucosal hyperenhancement, mural stratification, peripouch stranding, peripouch hyperemia, and peripouch abscess, fistula, or sinus tract), Liszewski et al [48] showed that IV Anorectal Disease contrast-enhanced CT enterography had a 90% sensitivity, 67% specificity, 90% PPV, 67% NPV, and 85% accuracy for diagnosis of pouchitis when more than 2 signs of inflammation were present. CT Pelvis The appropriate CT protocol for imaging a patient with an anorectal complaint depends upon the presentation and differential diagnosis. IV contrast is preferred to a noncontrast examination to help visualize and characterize fluid collections, abscesses, and fistulous tracts. CT without contrast is not useful in this clinical scenario. CT with and without IV contrast would only be useful when there is benefit from dual-phase imaging, but it is not typically performed in this scenario. Water-soluble rectal contrast is generally not necessary to diagnose a rectal abscess and may be challenging to administer, depending on symptom severity. However, rectal contrast may help delineate perforation or leak in a patient with a history of trauma or recent surgery. Water-soluble rectal contrast is preferred over barium to avoid the possibility of barium spilling into the peritoneal cavity or spaces of the extraperitoneal pelvis. Water-soluble rectal contrast is also preferred in patients who could potentially be undergoing surgery.


Anorectal Disease

Anorectal Disease. CT is often the initial examination for patients with clinical findings of proctitis or pouchitis because of its ability to evaluate inflammatory thickening of the rectal or pouch wall, associated abscess, possible fistula, or anastomotic leak in an IPAA. IV contrast-enhanced CT is preferred over a noncontrast CT because the presence of IV contrast will allow detection of abnormal enhancement of the bowel wall as well as the presence of rim-enhancement that would suggest abscess in any associated fluid collection. To our knowledge, there are no studies in the literature using modern CT technology that evaluate the accuracy of routine pelvic CT with or without IV contrast for the diagnosis of proctitis or pouchitis. FDG-PET/CT Skull Base to Mid-Thigh Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT has been reported to be a useful tool in assessing the degree of inflammatory activity in patients with ulcerative colitis and CD [49,50]. Shyn et al [51] compared FDG- PET/CT enterography to conventional CT enterography in evaluating patients with CD. In this study, FDG-PET/CT enterography showed sites of active inflammation in 3 of 13 cases (23.1%) that were not seen on CT enterography, though these areas were not in the rectum or a surgical pouch. To our knowledge, there is no relevant recent literature regarding the use of FDG-PET/CT in the evaluation of suspected proctitis or pouchitis. Fluoroscopy Contrast Enema Fluoroscopic contrast enemas performed for the diagnosis of perforation or leak, rectovaginal or rectovesicular fistula, pouchitis, or proctitis can be performed with water-soluble contrast or barium. In general, water-soluble contrast is preferred if a leak or perforation is suspected in order to avoid barium spillage into the peritoneal cavity or extraperitoneal pelvis. Using barium may also interfere with a subsequent CT scan because of the streak artifact that it causes on CT.


Anorectal Disease

Anorectal Disease. A retrospective review by Brown et al [52] published in 1990 compared CT to fluoroscopic examination of patients with IPAA. Some of the fluoroscopic examinations were performed antegrade through the distal limb of the loop ileostomy, whereas others were performed retrograde. In these 18 patients, 10 had infectious symptoms and 8 did not. CT more clearly delineated the site and extent of abscess in 9 patients with infectious symptoms compared with the fluoroscopic studies [52]. However, this study did not evaluate the sensitivity or specificity of each examination, neither did it directly address pouchitis. To our knowledge, there is no recent literature evaluating fluoroscopic contrast enema for the diagnosis of proctitis or pouchitis. MR Enterography Pouchitis can also be evaluated as part of MR enterography. MR enterography is commonly performed with biphasic oral contrast agents that produce low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences because they allow excellent characterization of bowel wall enhancement on IV contrast- enhanced T1-weigheted sequences. These agents include low weight/volume barium solutions, water, polyethylene glycol, and methylcellulose. Patients ingest a large volume of the oral contrast prior to the examination. Administering an antispasmodic drug such as glucagon is useful for reducing motion artifact caused by bowel peristalsis. Both FSE T2-weighted and steady-state free precession T2-weighted sequences are generally performed to compensate for limitations of each in addition to dynamic IV contrast-enhanced sequences. In 28 patients who underwent colectomy with IPAA, Sahi et al [53] compared MR enterography, pouch endoscopy, and biopsy. They found that the presence of 4 or more MR enterography features of inflammation had the best correlation with endoscopic findings (86% sensitivity, 79% specificity, 80% PPV, 85% NPV, and 82% accuracy). Anorectal Disease


Anorectal Disease

Anorectal Disease. MRI is an excellent imaging modality for the evaluation of inflammatory disease of the rectum or IPAA. Using IV contrast material enhances the ability to diagnose inflammation, adding the findings of mucosal hyperenhancement to other findings such as wall thickening, submucosal edema seen on T2-weighted sequences, and mucosal ulceration. Additional findings, such as perirectal and perianal fistula and abscess, can also be seen. In a study of 58 patients with CD who had MRI and colonoscopy, several MRI features correlated with endoscopic diagnosis of proctitis, including wall thickness, submucosal fat, increased perimural signal intensity on T2-weighted sequences, increased perimural enhancement, creeping fat, and mesorectal lymph node size [54]. In another study of 9 patients, MRI had sensitivity and specificity of 100% for pouchitis as validated by pathology, using the criteria of increased wall thickness and enhancement [55]. Radiography Pelvis Radiography is not useful in this clinical scenario because it cannot assess inflammation of the rectum or ileoanal pouch. There is no relevant literature to support the use of radiography in the evaluation of suspected proctitis or pouchitis. US Pelvis Various US techniques (transabdominal, transperineal, transvaginal, and endorectal) can be used to assess the rectum or IPAA. In one study using endorectal US to evaluate radiation proctitis as compared with colonoscopy, endorectal US had sensitivity of 86.4%, specificity of 66.7%, PPV of 76.0%, NPV of 80.0%, and overall accuracy of 77.5% in differentiating mild from severe radiation proctitis by using blurred rectal wall stratification and wall vascularity [56]. There is no relevant recent literature regarding the use of US in the evaluation of suspected pouchitis. WBC Scan Abdomen and Pelvis In 1990, Thoeni et al [57] published a retrospective study of 55 patients who underwent total colectomy and IPAA.


Anorectal Disease

Anorectal Disease. They compared CT, indium-11 (In-111) scintigraphy, and fluoroscopic pouchography for the detection of pouchitis, abscess, and fistula. For pouchitis, the sensitivity of CT, In-111 scintigraphy, and pouchography was 71%, 80%, and 53%, respectively. To our knowledge, there is no recent literature evaluating and comparing scintigraphy for the diagnosis of proctitis or pouchitis. There is no relevant recent literature regarding the use of Tc-99m white blood cell (WBC) scan in the evaluation of suspected proctitis or pouchitis. Anorectal Disease prolapse in the case of IPAA. A meta-analysis of complications after total proctocolectomy with IPAA performed by Hueting et al [59] showed a pooled incidence of 9.5% for pelvic sepsis, 5.5% for pouch-related anal or vaginal fistula, 9.2% for strictures, and 13.1% for small-bowel obstruction. The initial imaging modality for patients with a suspected postoperative complication may vary based upon the suspected complication. CT is often the first imaging modality used for patients who return following surgery with acute pain, sepsis, or signs of bowel obstruction. CT Abdomen and Pelvis CT abdomen and pelvis may be preferred over CT pelvis alone, depending upon the clinical scenario or specific type of operation performed. To our knowledge, there are no studies comparing noncontrast CT to IV contrast- enhanced CT for the detection of postoperative complications. However, IV contrast does improve the detection of abscesses and is important for the evaluation of the integrity of the bowel wall when ischemia or anastomotic dehiscence is suspected. CT with and without contrast would only be indicated when there is benefit from dual- phase imaging. When anastomotic leak is suspected, rectally administered contrast material is important to demonstrate extraluminal extravasation of contrast to confirm the leak, adding an additional finding to other findings of leak: perianastomotic gas, fluid collection, and staple line integrity.


Anorectal Disease

Anorectal Disease. Hyman et al [60] reported that CT was superior to fluoroscopic contrast enema at detecting leaks, with a PPV of 89.5% for CT and 40% for contrast enema in 33 patients who developed leaks. Kaur et al [61] showed a 91% sensitivity, 100% specificity, 100% PPV, and 95% NPV for CT in detecting postoperative anastomotic leaks in a retrospective study 170 patients who had undergone a low anterior resection, emphasizing the importance of rectal contrast material to improve confidence in diagnosis. CT Pelvis CT pelvis may be preferred over CT abdomen and pelvis in specific clinical scenarios when the pelvis alone is the area of clinical concern. To our knowledge there are no studies comparing noncontrast CT with IV contrast- enhanced CT for the detection of postoperative complications. However, IV contrast does improve the detection of abscesses and is important for the evaluation of the integrity of the bowel wall when ischemia or anastomotic dehiscence is suspected. CT with and without IV contrast would only be useful when there is benefit from dual- phase imaging. When anastomotic leak is suspected, rectally administered contrast material is important to demonstrate extraluminal extravasation of contrast to confirm the leak, adding an additional finding to other findings of leak: perianastomotic gas, fluid collection, and staple line integrity. Hyman et al [60] reported that CT was superior to fluoroscopic contrast enema at detecting leaks, with a PPV of 89.5% for CT and 40% for contrast enema in 33 patients who developed leaks. Kaur et al [61] showed a 91% sensitivity, 100% specificity, 100% PPV, and 95% NPV for CT in detecting postoperative anastomotic leaks in a retrospective study of 170 patients who had undergone a low anterior resection, emphasizing the importance of rectal contrast material to improve confidence in diagnosis.


Anorectal Disease

Anorectal Disease. Fluoroscopy Contrast Enema Fluoroscopic contrast enemas performed for the diagnosis of perforation or leak, rectovaginal or rectovesicular fistula, pouchitis, or proctitis can be performed with water-soluble contrast or barium. In general, water-soluble contrast is preferred if a leak or perforation are suspected in order to avoid barium spillage into the peritoneal cavity or extraperitoneal pelvis. Using barium may also interfere with a subsequent CT scan because of the streak artifact that it causes on CT. Fluoroscopic water-soluble contrast enema is routinely used to evaluate clinically suspected leaks, anastomotic stenoses, fistulas, and sinus tracts. It may be complementary to CT or performed in conjunction with CT. In the study by Tang et al [62], water-soluble contrast enema was performed in 33 of the 66 patients evaluated for pouch disorders and compared with a composite clinical diagnosis. The sensitivity and specificity for the diagnosis of small-bowel and inlet strictures was 80% and 95.7%, and pouch outlet strictures was 0% and 93.5%, respectively. They also found the sensitivity and specificity for the diagnosis of fistula was 33.3% and 96.3%, sinus tract 50% and 100%, pouch leak 50% and 96.8%, respectively [62]. In some institutions, routine water-soluble contrast enema is performed prior to ileostomy takedown. In a study of 42 patients who underwent total proctocolectomy with IPAA, Dolinsky et al [63] showed that 14% of patients had clinically significant occult strictures detected by water- soluble contrast enema prior to ileostomy takedown. On the other hand, others report that routine use of fluoroscopic water-soluble contrast enema in patients with low pelvic anastomoses (ultralow colorectal, coloanal, and IPAA) does not impact ileostomy takedown compared with digital rectal examination and colonoscopy or sigmoidoscopy.


Anorectal Disease

Anorectal Disease. In the study by Karsten et al [64], 38 patients were evaluated with fluoroscopic water-soluble contrast enema, which was 100% sensitive and 69% specific for detection of significant pathology, but that pathology was equally detected Anorectal Disease on digital rectal examination and endoscopic examinations such that fluoroscopic water-soluble contrast enema could be used selectively on patients with abnormal clinical findings. The superior contrast resolution of MRI compared with CT makes it an ideal modality for the evaluation of clinically suspected anastomotic or IPAA-related fistulas or sinus tracts. In a study of 44 patients with ulcerative colitis and IPAA with pelvic symptoms, MRI with and without IV gadolinium contrast material detected 23 of 26 fistula for a sensitivity of 88%, specificity of 100%, PPV of 100%, and NPV of 85% [65]. The authors reported that high diagnostic confidence was obtained with the IV gadolinium-enhanced sequence compared with the T2-weighted fat-saturated sequence. MRI was obtained in 23 of the 66 postoperative patients reported by Tang et al [62]. MRI had a sensitivity and specificity for the diagnosis of small-bowel and inlet strictures of 33.3% and 100%, pouch outlet strictures of 0% and 92%, fistula of 57.1% and 88.9%, sinus of 0% and 70.8%, and pouch leak of 0% and 91.7%, respectively. Radiography Abdomen and Pelvis Radiographs may be helpful in evaluating postoperative patients when there is a suspected bowel obstruction by confirming or excluding small-bowel obstruction. Radiographs may also show free air if there is a suspected postoperative perforation or ectopic air, or bubbly lucencies in the case of abscess, fistula, or sinus tracts that contain air. However, radiographs will frequently be inconclusive and additional imaging will be needed for those patients with abnormal radiographs; additional imaging is often necessary to confirm the suspected diagnosis and to add more specificity to the findings.


Anorectal Disease

Anorectal Disease. To our knowledge, there is no recent literature on the use of radiographs in the evaluation of suspected complications after proctectomy with coloanal or colorectal anastomosis and coloproctectomy with IPAA. 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. Anorectal Disease Anorectal Disease 20. Halligan S, Bartram CI. MR imaging of fistula in ano: are endoanal coils the gold standard? AJR Am J Roentgenol 1998;171:407-12. 21. Zbar AP, Armitage NC. Complex perirectal sepsis: clinical classification and imaging. Tech Coloproctol 2006;10:83-93. 22. Sahni VA, Ahmad R, Burling D. Which method is best for imaging of perianal fistula? Abdom Imaging 2008;33:26-30. 23. Lo Re G, Tudisca C, Vernuccio F, et al. MR imaging of perianal fistulas in Crohn's disease: sensitivity and specificity of STIR sequences. Radiol Med 2016;121:243-51. 24. Yildirim N, Gokalp G, Ozturk E, et al. Ideal combination of MRI sequences for perianal fistula classification and the evaluation of additional findings for readers with varying levels of experience. Diagn Interv Radiol 2012;18:11-9. 25. Visscher AP, Felt-Bersma RJ. Endoanal ultrasound in perianal fistulae and abscesses. Ultrasound Q 2015;31:130-7. 26. Buchanan GN, Bartram CI, Williams AB, Halligan S, Cohen CR. Value of hydrogen peroxide enhancement of three-dimensional endoanal ultrasound in fistula-in-ano. Dis Colon Rectum 2005;48:141-7. 27. Sun Y, Cui LG, Liu JB, Wang JR, Ping H, Chen ZW. Utility of 360 degrees Real-time Endoanal Sonography for Evaluation of Perianal Fistulas. J Ultrasound Med 2018;37:93-98. 28. Buchanan GN, Halligan S, Bartram CI, Williams AB, Tarroni D, Cohen CR.


Anorectal Disease

Anorectal Disease. Clinical examination, endosonography, and MR imaging in preoperative assessment of fistula in ano: comparison with outcome-based reference standard. Radiology 2004;233:674-81. 29. Cheong DM, Nogueras JJ, Wexner SD, Jagelman DG. Anal endosonography for recurrent anal fistulas: image enhancement with hydrogen peroxide. Dis Colon Rectum 1993;36:1158-60. 30. West RL, Zimmerman DD, Dwarkasing S, et al. Prospective comparison of hydrogen peroxide-enhanced three- dimensional endoanal ultrasonography and endoanal magnetic resonance imaging of perianal fistulas. Dis Colon Rectum 2003;46:1407-15. 31. Brillantino A, Iacobellis F, Reginelli A, et al. Preoperative assessment of simple and complex anorectal fistulas: Tridimensional endoanal ultrasound? Magnetic resonance? Both? Radiol Med 2019;124:339-49. 32. Senatore PJ, Jr. Anovaginal fistulae. Surg Clin North Am 1994;74:1361-75. 33. Andreani SM, Dang HH, Grondona P, Khan AZ, Edwards DP. Rectovaginal fistula in Crohn's disease. Dis Colon Rectum 2007;50:2215-22. 34. Champagne BJ, McGee MF. Rectovaginal fistula. Surg Clin North Am 2010;90:69-82, Table of Contents. 35. Kuhlman JE, Fishman EK. CT evaluation of enterovaginal and vesicovaginal fistulas. J Comput Assist Tomogr 1990;14:390-4. 36. Giordano P, Drew PJ, Taylor D, Duthie G, Lee PW, Monson JR. Vaginography--investigation of choice for clinically suspected vaginal fistulas. Dis Colon Rectum 1996;39:568-72. 37. Wychulis AR, Pratt JH. Sigmoidovaginal fistulas. A study of 37 cases. Arch Surg 1966;92:520-4. 38. Amendola MA, Agha FP, Dent TL, Amendola BE, Shirazi KK. Detection of occult colovesical fistula by the Bourne test. AJR Am J Roentgenol 1984;142:715-8. 39. Hsieh JH, Chen WS, Jiang JK, Lin TC, Lin JK, Hsu H. Enterovesical fistula: 10 years experience. Zhonghua Yi Xue Za Zhi (Taipei) 1997;59:283-8. 40. Botsikas D, Pluchino N, Kalovidouri A, et al. CT vaginography: a new CT technique for imaging of upper and middle vaginal fistulas. Br J Radiol 2017;90:20160947. 41. Coe FO. Vaginography.


Recurrent Lower Urinary Tract Infections in Females.  Introduction/Background A urinary tract infection (UTI) is an infection of the urinary system causing an inflammatory response. A UTI occurs when the normal flora of the periurethral area are replaced by uropathogenic bacteria, which ascend, causing bacterial cystitis. Less commonly, this infection ascends to the kidney to cause bacterial pyelonephritis [1]. The overall lifetime risk of UTI for women is >50% [2]. An uncomplicated UTI is classified as a UTI without structural or functional abnormalities of the urinary tract and without relevant comorbidities. It should be noted that although uncomplicated UTI includes both lower tract infection (cystitis) and upper tract infection (pyelonephritis), repeated pyelonephritis should prompt consideration of a complicated etiology [1]. Complicated UTIs are those occurring in patients with underlying structural or medical problems [3,4]. Anatomical abnormalities include cystoceles, bladder or urethral diverticula, fistulae, indwelling catheters, urinary tract obstruction and underlying conditions such as voiding dysfunction, pregnancy, diabetes, and immunosuppression. Other documented risk factors include prior urinary tract surgery or trauma, gross hematuria after infection resolution, urea-splitting bacteria on culture, prior abdominopelvic malignancy, prior urinary tract calculi, prior diverticulitis, symptoms of pneumaturia, fecaluria, or repeated pyelonephritis. In the nonobstructed, nonpregnant woman, uncomplicated UTI is usually treated empirically and responds to appropriate antimicrobial therapy [2,5]. A UTI is considered recurrent when it follows the complete clinical resolution of a previous UTI [6]. Recurrent lower UTIs are usually defined as at least three episodes of infection within the preceding 12 months [3]. Recurrent UTIs involve reinfection from a source outside of the urinary tract or from bacterial persistence [1-3].


Recurrent Lower Urinary Tract Infections in Females. In most cases, such infections are the result of sexual habits and hygiene (eg, women who are sexually active, especially those using diaphragms and/or spermatocides) [3,7]. Although antibiotic prophylaxis effectively limits UTI recurrence, it increases the risk of antibiotic resistance for both the causative microorganisms and the indigenous flora and risks adverse effects. It therefore should be approached judiciously. Before considering antibiotic prophylaxis for recurrent UTIs, self-care measures should be advised, including ensuring adequate hydration to promote more frequent urination, encouraging urge-initiated voiding and post-coital voiding, the avoidance of spermicidal-containing contraceptives, and, for postmenopausal women with risk factors such as atrophic vaginitis, the prescription of topical vaginal estrogens, as appropriate [8,9]. A clean-catch or catheterized specimen for culture typically reveals >100,000 organisms per milliliter of urine. E. coli is the most common organism in all patient groups, causing approximately 75% of recurrent UTIs, with most other infections caused by E. faecalis, Proteus mirabilis, Klebsiella, or S. saprophyticus particularly in patients with risk factors for complicated UTIs [6,10-12]. Postmenopausal women are at increased risk for recurrent UTI in the presence of urinary incontinence, cystocele, or high postvoid residuals of urine [13,14]. Women who have three or more symptomatic infections over a 12-month period may benefit from prophylaxis [3,4,7]. Imaging is of low yield in patients without underlying risk factors, less than two episodes per year on average, and who respond promptly to appropriate therapy (see Appendix 1) [1,7,15,16]. Current clinical guidelines indicate that imaging should not be routinely obtained in the index patient presenting with recurrent UTIs because aThe University of Texas MD Anderson Cancer Center, Houston, Texas. bPanel Chair, University of Chicago, Chicago, Illinois.


Recurrent Lower Urinary Tract Infections in Females. cPanel Vice-Chair, Duke University Medical Center, Durham, North Carolina. dMemorial Sloan Kettering Cancer Center, New York, New York. eMayo Clinic, Jacksonville, Florida. fMcGill University, Montreal, Quebec, Canada. gMayo Clinic, Rochester, Minnesota. hUrology Clinics of North Texas, Dallas, Texas; American Urological Association. iUniversity of Pennsylvania School of Medicine, Philadelphia, Pennsylvania; American Society of Nephrology. jUniversity of Wisconsin, Madison, Wisconsin. kUPMC, Pittsburgh, Pennsylvania; American Urological Association. lStanford University Medical Center, Stanford, California. mOttawa Hospital Research Institute and the Department of Radiology, The University of Ottawa, Ottawa, Ontario, Canada. nEmory University Hospital, Atlanta, Georgia. oNational Institutes of Health, Bethesda, Maryland. pSpecialty Chair, University of Alabama at Birmingham, Birmingham, Alabama. 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 Special Imaging Considerations CTU CT urography (CTU) is an imaging study that is tailored to improve visualization of both the upper and lower urinary tracts. There is variability in the specific parameters, but it usually involves unenhanced images followed by intravenous (IV) contrast-enhanced images, including nephrographic and excretory phases acquired at least 5 minutes after contrast injection. Alternatively, a split-bolus technique uses an initial loading dose of IV contrast and then obtains a combined nephrographic-excretory phase after a second IV contrast dose; some sites include arterial phase. CTU should use thin-slice acquisition.


Recurrent Lower Urinary Tract Infections in Females. Reconstruction methods commonly include maximum intensity projection or 3-D volume rendering. For the purposes of this document, we make a distinction between CTU and CT abdomen and pelvis without and with IV contrast. CT abdomen and pelvis without and with IV contrast is defined as any protocol not specifically tailored for evaluation of the upper and lower urinary tracts and without both the precontrast and excretory phases, as is the case for CTU. CT Pelvis with Bladder Contrast (CT Cystography) CT cystography is an imaging study that is tailored to visualize traumatic bladder lesions. This technique involves retrograde drip infusion of diluted iodinated contrast into the urinary bladder followed by pelvic CT imaging at maximal bladder distension. IV contrast may be administered, particularly if evaluating for underlying neoplastic or inflammatory processes [19]. For the purposes of this document, we distinguish CT cystography from CT abdomen and pelvis without and with IV contrast. CT abdomen and pelvis without and with IV contrast is also defined as any protocol not specifically tailored for evaluation of the integrity of the urinary bladder wall and without retrograde instillation of contrast into the urinary bladder, as is the case for CT cystography. MRU MR urography (MRU) is also tailored to improve imaging of the urinary system. Unenhanced MRU relies upon heavily T2-weighted imaging of the intrinsic high signal intensity from urine for evaluation of the urinary tract. IV contrast is administered to provide additional information regarding obstruction, urothelial thickening, focal lesions, and stones. A contrast-enhanced T1-weighted series should include corticomedullary, nephrographic, and excretory phase. Thin-slice acquisition and multiplanar imaging should be obtained. For the purposes of this document, we make a distinction between MRU and MRI abdomen and pelvis without and with IV contrast.


Recurrent Lower Urinary Tract Infections in Females. MRI abdomen and pelvis without and with IV contrast is defined as any protocol not specifically tailored for evaluation of the upper and lower urinary tracts, without both the precontrast and excretory phases and without heavily T2-weighted images of the urinary tract, as is the case for MRU. US Abdomen with IV Contrast Prior studies show promise regarding the potential role of contrast-enhanced ultrasound (US) for the initial diagnosis and follow-up of patients with complicated acute pyelonephritis [20-22]. Using CT as a reference standard, Mitterberger et al [22] demonstrated a sensitivity of 98% and a specificity of 100% for contrast-enhanced US in the diagnosis of acute pyelonephritis in 100 patients. Its use in current mainstream practice remains limited, however, with only recent FDA approval for abdominal imaging applications. Recurrent Lower Urinary Tract Infections in Females Discussion of Procedures by Variant Variant 1: Recurrent lower urinary tract infections in a female. Uncomplicated with no underlying risk factors. In women with recurrent uncomplicated UTIs, cystoscopy and imaging are not routinely used [1]. Lawrentschuk et al [23] showed that women with no risk factors for UTI had a negative predictive value of 93% for normal cystoscopy. Prior series have demonstrated a low yield of nonincidental findings in those patients with a low pretest probability of complicated UTI [1,24]. CT Abdomen and Pelvis There are no specific guidelines recommending imaging studies in women who have recurrent UTIs but no known underlying medical or anatomic conditions [6,25]. As such, CT is not generally performed for evaluation of uncomplicated UTI. CT Pelvis with Bladder Contrast (CT Cystography) There are no specific guidelines recommending imaging studies in women who have recurrent UTIs but no known underlying medical or anatomic conditions [6,20]. As such, CT cystography is not generally performed for evaluation of uncomplicated UTI.


Recurrent Lower Urinary Tract Infections in Females. CTU There are no specific guidelines recommending imaging studies in women who have recurrent UTIs but no known underlying medical or anatomic conditions [6,20]. As such, CTU is not generally performed for evaluation of uncomplicated UTI. Fluoroscopy Contrast Enema Although fluoroscopic contrast enema may be useful in the setting of suspected vesicoenteric fistula, it is not used for imaging in women with recurrent uncomplicated UTIs in the absence of risk factors. Fluoroscopy Cystography A prior prospective study of findings with excretory urography, cystography, and cystoscopy in women with symptomatic UTI revealed only rare instances of abnormalities important in the treatment of UTI in this group of patients, primarily urethral diverticula [26]. Most women with recurrent uncomplicated UTIs in the absence of risk factors have normal urinary tracts and do not routinely require imaging with fluoroscopic cystography. Fluoroscopy Voiding Cystourethrography As most women with recurrent uncomplicated UTIs in the absence of risk factors have normal urinary tracts, they do not routinely require imaging with voiding cystourethrography. A prior prospective study including findings of excretory urography in women with symptomatic UTI revealed only rare instances of structural abnormalities important in the treatment of UTI in this group of patients [26]. MRI Abdomen and Pelvis CT and MRU have supplanted the use of IV urography (IVU) at most institutions for most types of urinary applications [27]. However, most women with recurrent uncomplicated UTIs in the absence of risk factors have normal urinary tracts and do not routinely require imaging with MRI. MRU CT and MRU have supplanted the use of IVU at most institutions for most types of urinary applications [27]. However, most women with recurrent uncomplicated UTIs in the absence of risk factors have normal urinary tracts and do not routinely require imaging with MRI.


Recurrent Lower Urinary Tract Infections in Females. Radiography Abdomen As most women with recurrent symptomatic UTI have normal urinary tracts, they do not routinely require imaging with radiography of the abdomen. Radiography Intravenous Urography Historically, intravenous urography (IVU) was the imaging study of choice to evaluate the urinary tract, but it is no longer used at most institutions [13]. IVU is not used for evaluation of uncomplicated UTI. US Kidneys and Bladder Retroperitoneal As most women with recurrent symptomatic UTI have normal urinary tracts, they do not routinely require imaging with US of the kidneys, bladder, and retroperitoneum. Recurrent Lower Urinary Tract Infections in Females Variant 2: Recurrent lower urinary tract infections in a female. Complicated, or patients who are nonresponders to conventional therapy, develop frequent reinfections or relapses, or have known underlying risk factors. Complicated causes of UTI can be evaluated by history and physical examination. In women suspected of having a recurrent complicated UTI, cystoscopy and imaging should be considered [24]. CT Abdomen and Pelvis Historically, unenhanced CT has been used predominantly for the emergency patient with renal colic and/or hematuria. It has also been used to define the severity and extent of upper tract calculi, which are occasionally associated with recurrent complicated UTIs. The lack of additional contrast-enhanced CT imaging and the lack of dedicated imaging of the collecting systems, kidneys, and bladder limits further evaluation of underlying anatomical or pathophysiologic processes. Contrast-enhanced CT has been used effectively to evaluate a range of urinary tract abnormalities, including renal masses, genitourinary trauma, and specific aspects of renal infection, including the presence of pyelonephritis, renal abscesses, and obstruction.


Recurrent Lower Urinary Tract Infections in Females. However, a contrast-enhanced CT of the abdomen and pelvis remains a study that is not tailored for evaluation of the urothelium and therefore does not optimally evaluate the collecting systems, ureters, and bladder. Moreover, lacking an unenhanced CT component, a contrast-enhanced CT of the abdomen and pelvis can limit the detection of calculi and the characterization of enhancement within masses [24]. The addition of rectal contrast or oral contrast with delayed scanning of an enhanced CT of the abdomen and pelvis is useful to detect enterovesical fistulas and infected fistulous tracts [28]. CT Pelvis with Bladder Contrast (CT Cystography) CT cystography has supplanted fluoroscopic cystogram for the evaluation of traumatic bladder injuries, including intraperitoneal, extraperitoneal, or combined rupture and bladder contusions [29]. It is also useful for diagnosing bladder fistulas and leaks, particularly colovesical fistulas occurring as a result of sigmoid diverticular disease, which can remain undiagnosed despite evaluation with cystoscopy and contrast-enhanced CT [19]. CTU CTU CTU is a primary test for the evaluation of recurrent complicated UTIs. It includes unenhanced, nephrographic phase, and excretory phase images, with the latter providing a detailed anatomic depiction of each of the major portions of the urinary tract including the kidneys, intrarenal collecting systems, ureters, and bladder [30]. Diuretic administration prior to the excretory phase can augment both urinary tract distention and opacification [30]. CTU has excellent sensitivity and specificity for the identification of renal and urothelial lesions [31]. This allows patients with hematuria to be evaluated comprehensively and can identify abnormalities of the collecting systems [27]. It is also useful for detecting or excluding congenital anomalies or obstruction of the urinary tract in patients with complicated recurrent UTIs.


Recurrent Lower Urinary Tract Infections in Females. Given the low yield of CTU screening for asymptomatic hematuria in patients <30 years of age, or without risk factors for urinary tract malignancy, US or noncontrast CT may be the first-line imaging examinations in these patients. When there are risk factors present for urinary tract malignancy and the patient is >50 years of age, CTU is the preferred examination [31]. Fluoroscopy Contrast Enema Contrast enema is generally not useful for women with recurrent complicated UTIs. Although it may be utilized for imaging of vesicoenteric fistulas, CT is the primary imaging modality for suspected cases of enterovesical fistulas and has been found to have a higher rate of detection and also capable of identifying the underlying etiology [32,33]. If an enema is performed, water-soluble contrast should be selected rather than barium. Fluoroscopy Cystography Fluoroscopic cystography is generally not useful for women with recurrent complicated UTIs. Although it can delineate bladder diverticuli and vesicoenteric fistulas, CT has supplanted fluoroscopic cystography at most institutions. Fluoroscopy Urethrography Double Balloon Double-balloon urethrography can be useful for demonstration of urethral diverticula, although MRI best assesses the structure and complexity of urethral diverticula, allowing for accurate diagnosis and improved surgical planning. MRI to evaluate for urethral diverticulum has replaced double-balloon urethrography at most institutions. Double- balloon urethrography can be technically difficult and may be uncomfortable for the patient. For this document, it is assumed the procedure is performed and interpreted by an expert. Recurrent Lower Urinary Tract Infections in Females Fluoroscopy Voiding Cystourethrography When a bladder diverticulum is at or near a ureteral orifice, voiding cystourethrography can be considered to evaluate the possibility of vesicoureteral reflux [34].


Recurrent Lower Urinary Tract Infections in Females. It can also be employed for imaging of suspected bladder or urethral fistula, urethral diverticulum, or bladder prolapse. MRI Abdomen and Pelvis Both MRI of the abdomen and pelvis and MRU can be used to evaluate the urinary tract and have the advantage to provide more functional information than CT. MRI has been shown to be useful in the diagnosis and follow-up of UTI and acute pyelonephritis [27,35,36]. MRI is effective at diagnosing pelvic-organ prolapse. The resultant cystoceles and urinary incontinence associated with pelvic-organ prolapse are significant risk factors for recurrent UTIs in postmenopausal women [13,37,38]. MRI is the optimum imaging modality for assessment of the structure and complexity of urethral diverticula, allowing for accurate diagnosis and improved surgical planning [39]. Given the excellent soft-tissue contrast on MRI, this modality is equally sensitive to CT for evaluating vesicovaginal and enterovesicular fistulae [40,41]. In at least one study, MRI altered the surgical management in 15% of patients [39]. A history of recurrent UTI is seen in 30% to 50% of patients with urethral diverticula. Diverticula of the urethra can be evaluated with high sensitivity and specificity by double-balloon urethrography, voiding CT urethrography, and MRI [42-44]. MRI best assesses the structure and complexity of urethral diverticula, allowing for accurate diagnosis and improved surgical planning. Patients with suspected bladder diverticula may be imaged with cystography, US, or CT [45]. Bladder diverticula are unusual in women and are associated with a neurogenic or postoperative bladder; they are rarely congenital. MRI has also been shown to be accurate in the diagnosis of colovesical fistula. The multiplanar imaging capability and high soft-tissue resolution inherent to MRI also makes this modality suitable for imaging suspected fistulae, particularly when repeat imaging is an issue [40,41].


Recurrent Lower Urinary Tract Infections in Females. IVU, US, and upper gastrointestinal or small-bowel follow-through have very low yields for fistula [46,47]. MRU MRU is useful to evaluate suspected urinary tract obstruction, hematuria, and congenital anomalies, as well as postoperative anatomy. The most common MRU techniques for displaying the urinary tract can be divided into two categories: static-fluid MRU and excretory MRU. Static-fluid MRU makes use of heavily T2-weighted sequences to image the urinary tract as a static collection of fluid, can be repeated sequentially (cine MRU) to better demonstrate the ureters in their entirety and to confirm the presence of fixed stenoses, and is most successful in patients with dilated or obstructed collecting systems. Excretory MRU is performed during the excretory phase of enhancement after the IV administration of gadolinium-based contrast material. Diuretic administration is integral to excretory MRU to better demonstrate nondilated systems. Static-fluid and excretory MRU can be combined with conventional MRI for comprehensive evaluation of the urinary tract [48]. MRU can be used to evaluate the urinary tract and provides more functional information than CT provides. However, MRU is less established and less reliable and thus results in lesser diagnostic image quality relative to CTU [23]. In comparison to CTU, it necessitates a longer examination time and is less sensitive than CT for detecting urinary tract calculi. In a study of 149 patients, MRU demonstrated 69% sensitivity for detecting calculi versus 100% for CT [49]. However, MRU has shown increased sensitivity for perirenal fluid and ureteric dilatation in comparison with CT in the setting of acute obstruction [50]. Multiplanar reconstruction images in the coronal and sagittal planes are commonly included in MRU images to improve visualization of urinary tract abnormalities [27,48].


Recurrent Lower Urinary Tract Infections in Females. Additional benefits for MRU are in documenting active upper-tract infection versus scar formation to determine whether therapy has been effective in the high-risk patient. Radiography Abdomen Radiography of the abdomen has long been employed for the detection of calculi, intramural bladder wall calcification, gas in the wall or lumen of the urinary bladder, and/or foreign bodies that may be the etiology of a UTI. Use of digital tomosynthesis of the abdomen results in improved detection of urinary stones in general over digital radiography [51]. Bladder-wall calcification, when present, is typically due to prior infection with Schistosoma (uncommon in the United States, but very common in other parts of the world), tuberculosis, Cytoxan cystitis, or radiation cystitis [52]. For women with recurrent UTIs, however, abdominal radiography is generally not a useful diagnostic tool as other imaging modalities have higher sensitivity and specificity in this setting. Recurrent Lower Urinary Tract Infections in Females Radiography Intravenous Urography CT and MRU have supplanted the use of IVU for evaluation of urinary abnormalities at most institutions [27], and it is generally not useful for women with recurrent complicated UTIs. US Kidneys and Bladder Retroperitoneal US may be useful in women with recurrent UTIs, particularly prior to pregnancy, to evaluate for hydronephrosis and risk factors for recurrent infection. Hydronephrosis can be demonstrated as an indication of obstruction, although US may not yield a specific etiology [53-55]. US is a useful initial screening tool for obstructive uropathy and for postvoid residual volume determination to detect incomplete bladder emptying [56]. It should be noted, although US can detect renal stones, it is generally less sensitive than CT [57-59]. Renal abscess or perinephric collections can also be detected sonographically, and US of the bladder can be employed to evaluate for bladder diverticula detection [45].


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain.  Diagnostic imaging plays a key role in the assessment of acute elbow pain. A thorough understanding of diagnostic imaging modalities is essential to expeditiously identify the damaged structures and assist in treatment/surgical planning, thus allowing for rapid return to play/activity. In a more recent study, the same authors tested joint widening on cadaveric human elbows at various stages of ligamentous transection. The 5 sequential stages, evaluated with varus stress, included 1) intact, 2) transection of the lateral ulnar collateral ligament (UCL), 3) complete transection of the lateral collateral ligament complex, 4) transection of the anterior aspect of the capsule, and 5) transection of the medial collateral ligament. The 5 sequential stages, evaluated by valgus stress, included 1) intact, 2) transection of the anteromedial collateral ligament, 3) complete transection of the medial collateral ligament, 4) transection of the anterior capsule, and 5) transection of Reprint requests to: publications@acr.org Acute Elbow and Forearm Pain the lateral collateral ligamentous complex. The authors concluded that dynamic fluoroscopy makes it possible to distinguish among different stages of collateral ligament injury of the elbow [5]. OR Discussion of Procedures by Variant Variant 1: Adult. Acute elbow or forearm pain. Initial imaging. Bone Scan Area of Interest There is no evidence to support the use of 3-phase bone scan as the initial imaging study for the evaluation of acute elbow and forearm pain. CT Area of Interest With IV Contrast There is no evidence to support the use of contrast-enhanced CT of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. CT Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced CT of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain.


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. CT Area of Interest Without IV Contrast There is no evidence to support the use of noncontrast CT of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. MRI Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced MRI of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. MRI Area of Interest Without IV Contrast There is no evidence to support the use of contrast-enhanced MRI of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. Radiography Area of Interest Radiographs are beneficial as the initial imaging assessment for acute elbow and proximal forearm pain. Conventional radiographs are often the first-imaging modality used to exclude a fracture or dislocation. In adults, the most frequent fracture involves the radial head or neck and accounts for 50% of cases [1]. An elbow joint effusion can be identified on conventional radiography with the presence of posterior and anterior fat pad elevation. In combination with the clinical context of acute trauma, the presence of a joint effusion can imply an occult elbow fracture. Avulsion fractures can also be identified at the attachment sites of tendons and ligaments. Occasionally, triceps tendon tears may result in avulsion fractures of the olecranon or an olecranon enthesophyte. Injuries to the coronoid process are sequela of prior elbow dislocation, which is typically associated with soft tissue injury. As such, coronoid process fractures should prompt the referring provider to assess for associated tendon or ligament injury because these are commonly associated with elbow dislocation. US Area of Interest There is limited evidence to support the use of ultrasound (US) of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. Acute Elbow and Forearm Pain


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. Variant 2: Adult. Acute elbow or forearm pain. Suspect fracture. Radiographs normal or indeterminate. Next imaging study. This variant is associated with osseous injury only. Please refer to Variant 3 for recommendations for the evaluation of soft tissue injury. Bone Scan Area of Interest There is no evidence to support the use of 3-phase bone scan as the initial imaging study for the evaluation of acute elbow and forearm pain. CT Area of Interest With IV Contrast There is no evidence to support the use of contrast-enhanced CT of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. CT Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced CT of the elbow/proximal forearm as the initial imaging study for the evaluation of acute elbow and forearm pain. In the elbow, the additional knowledge gleaned from CT includes size of fracture fragments and amount of displacement or angulation, which may affect the surgical treatment options. Isolated radial head fractures, Essex- Lopresti injuries, and Monteggia fractures with dislocation of the elbow can be diagnosed. Traumatic elbow injuries are categorized into radial head fracture with posterior dislocation, terrible triad injury, posterior and anterior fracture-dislocation, trans-olecranon (anterior) fracture-dislocation, and varus posteromedial rotational instability. Fracture mapping and quantitative 3-D CT analysis of coronoid and olecranon fractures have identified specific shapes, sizes, and orientations of fracture fragments according to a pattern of traumatic elbow instability.


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. Specifically, with regards to proximal olecranon fractures, plate and screw constructs tend to have only a few short proximal screws, and further stabilization with a supplementary wire or suture fixation incorporating the triceps attachment has been found to be helpful and knowledge of the fracture morphology is helpful for this surgical planning. Furthermore, CT can assess the degree of ulnohumeral incongruity, which is inversely proportional to the proximal olecranon fracture size [8]. MRI Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced MRI of the elbow/proximal forearm as the next imaging study for the evaluation of occult fracture of the elbow and/or proximal forearm. MRI Area of Interest Without IV Contrast There is no evidence to support the use of noncontrast MRI of the elbow/proximal forearm as the next imaging study for the evaluation of occult fracture of the elbow and/or proximal forearm. In the setting of the Osborne- Cotterill lesion, occasionally the impaction, avulsion, and shear fracture of the posterolateral capitellum during elbow fracture-dislocation could be nondisplaced on CT; however, MRI is able to demonstrate the injury with marrow edema at the fracture site [9]. Radiography Area of Interest Repeat in 10-14 Days Pavic et al [10] evaluated 193 patients with acute elbow trauma with no acute fracture identified at the time of initial radiographic evaluation. Of note, these patients all had elbow joint effusions. Follow-up conventional radiographs were performed in 184 patients (95%) and showed fractures of the radial neck in 58% and nondisplaced fractures of the radial head in 37% of cases. Five percent of patients continued to have normal radiographs and were further evaluated with MRI and found to have intraarticular joint effusions, bone contusion, and radial and UCL ruptures.


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. Acute Elbow and Forearm Pain US Area of Interest There is no evidence to support the use of diagnostic US of the elbow/proximal forearm as the imaging study for the evaluation of acute elbow and forearm pain. There are 2 studies discussing point-of-care US that are too small to support use in this setting [11,12]. Variant 3: Adult. Acute elbow or forearm pain. Suspect tendon or ligament or muscle injury. Radiographs normal or indeterminate. Next imaging study. Bone Scan Area of Interest There is no evidence to support the use of 3-phase bone scan for the assessment of tendon, ligamentous, or muscle injury. CT Area of Interest With IV Contrast There is no evidence to support the use of contrast-enhanced CT of the elbow/proximal forearm for the assessment of tendon, ligamentous, or muscle injury. CT Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced CT of the elbow/proximal forearm for the assessment of tendon, ligamentous, or muscle injury. CT Area of Interest Without IV Contrast There is no evidence to support the use of noncontrast CT of the elbow/proximal forearm for the assessment of tendon, ligamentous, or muscle injury. MRI Area of Interest Without and With IV Contrast There is no evidence to support the use of noncontrast/contrast-enhanced MRI of the elbow/proximal forearm as the for the assessment of tendon, ligamentous, or muscle injury. MRI Area of Interest Without IV Contrast Several studies have evaluated the use of noncontrast MRI in the assessment for ligamentous and tendinous injury [13]. Tarallo et al showed the best interobserver agreement in the assessment of lateral collateral complex injuries and the worst interobserver reliability for the UCL [7,14-18]. Athletes are prone to both acute and chronic overuse injuries of the elbow [13]. In a study of elbow injuries incurred during participation of the Rio de Janeiro 2016 Summer Olympic Games, Alizai et al [20] showed a predominance of UCL injury.


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. For the purposes of this document, it is difficult to ascertain the acuity of the injuries from this report. Furthermore, MRI is particularly useful in the assessment of biceps tears [21-24]. MRI has an improved sensitivity for the detection of partial tears of the biceps and triceps tendons. In a study of 77 patients, Nicolay et al [24] showed partial rupture of the long head of the biceps with an intact short head of the biceps to be the most common injury. On the other hand, isolated complete ruptures of the long head represented the least common injury pattern. Traumatic ruptures had a significantly higher association with ruptures of the short head of the biceps tendon, whereas ruptures of the long head of the biceps tendon accounted for 89% of atraumatic ruptures. Acute Elbow and Forearm Pain diagnosis of partial distal biceps tendon tears. However, the interrater reliability was better for FABS view and significantly more accurate than surgical findings in grading the extent of pathology. MRI is also useful in the assessment of rare triceps tears [21-24]. Lee et al [23] evaluated a small subset of patients and found 2 major causes for acute traumatic rupture of the triceps tendon at the elbow. A fall on an outstretched hand was categorized as an indirect injury, whereas a direct blow to the triceps by an object was considered a direct injury. The authors found that the indirect injury was most likely to result in injury of the lateral and long heads of the distal triceps tendon with an intact medial head tendon. Direct injuries were more likely to have a full-thickness rupture with an odds ratio of 1.75 (95% confidence interval, 0.92-3.32; P = . 02). In addition, they found that the indirect injuries had associated ligamentous injuries with an odds ratio of 0.13 (95% confidence interval, 0.02-0.78; P < . 001). However, one paper noted the overestimation of triceps tear severity compared with surgical assessment [28].


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. US Area of Interest The use of US to evaluate the distal biceps tendon is well described in the literature [21,29,30]. A study by de la Fuente et al [30] investigated the sensitivity of US in detecting injuries of the distal biceps brachii tendon. The authors compared US examinations with MRI and surgery and found a slight statistical advantage of US over MRI. However, US is at a disadvantage with regard to the detection of partial tearing and tendinopathy. Lynch et al [31] showed the accuracy of US in the diagnosis of complete distal biceps tendon rupture was inferior to MRI, 45.5% compared with 86.4%. The accuracy rate of US to detect partial tears of the biceps was the same as MRI at 66.7%. The sensitivity and specificity of US for the detection of biceps tendon tears were 62.5% and 20.0%, respectively, inferior to MRI at 76% and 50%. The authors concluded that MRI is a more accurate imaging modality at correctly identifying the type of distal biceps tendon tear, thus enabling the orthopedic surgeon to provide a more precise treatment plan. Deschrijver et al [32] conducted an extensive literature search and meta-analysis to assess the usefulness of clinical examination testing as well as the usefulness of US. They further investigated whether supplementary sonographic views/maneuvers (eg, posterior approach Cobra technique, lateral approach supinator view, and medial approach pronator view) added benefit to the standard US examination. Their conclusion was that US can be considered an alternative to MRI in the evaluation of the distal biceps tendon ruptures. In a recent study by Miller et al, it was shown that radiologists preferred the medial imaging approach. Furthermore, this particular imaging approach demonstrated substantial interreader agreement [33]. Triceps tendon ruptures are rare, and a handful of studies have shown that US can identify both complete and isolated partial tears of the triceps brachii tendon [34,35].


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. In addition, in a feasibility study, Barret et al [12] showed that traumatic ligamentous lesions could be detected on US examination with the identified pathology matching the clinical symptomatology. Of note, no traumatic ruptures of the flexor or extensor tendon origins were detected on this study; however, this was a small study with only 9 patients. Assessment of the anterior bundle of the UCL in athletes is well documented and thus could be useful in the setting of acute trauma as well [20,36-38]. The ability of US to visualize tendinous and ligamentous structures in cadaveric and normal volunteers of the medial and lateral elbow is well accepted; however, there are few articles evaluating its usefulness in the acute setting. A case report by van Duijn and Felton [39] described a case of an 18-year-old collegiate baseball pitcher with preinjury and postinjury US with MR arthrographic correlation. This patient was already participating in a research study evaluating the reliability of UCL thickness measurements using US imaging. In this study, the preinjury US image showed a normal hyperechoic appearance of the anterior band of the UCL. Postinjury images showed disruption of the ligamentous fibers of the anterior band of the UCL, with a large hypoechoic gap separating the 2 torn ends of the UCL, which was confirmed at the time of MR arthrography. A single study by Bilger et al [40] evaluated the use of US in the acute phase of closed elbow injuries and found a strong interrater reliability for injuries of the radial collateral, annular, and anterior bundle of the medial collateral ligaments. They further showed 100% US-surgical correlation in a subset of patients who had surgery. In a cadaveric study, Arrigoni et al [41] evaluated the lateral compartment of the elbow after release of the anterior half of the common extensor origin and after complete radial collateral ligament release. They concluded that US evaluation can detect changes related to tendon tears or


Acute Elbow and Forearm Pain

Acute Elbow and Forearm Pain. Acute Elbow and Forearm Pain muscular avulsions of the common extensor origin and can depict lateral elbow compartmental pathologic laxity as evidence by widening of the articular joint space under dynamic stress maneuvers. Unfortunately, accurate identification of injuries to the lateral collateral ligament was not reliable. The majority of literature using US for the diagnosis of tendinous injuries is found in the setting of chronic elbow pain, particularly in the athlete. US of the elbow has moderate agreement with MRI of the elbow for the diagnosis and grading of common extensor tendon tears, with the sensitivity, specificity, and accuracy reported at 64.52%, 85.19%, and 72.73%, respectively [42]. Sonoelastography has shown promise for the detection of medial epicondylalgia with a sensitivity, specificity, accuracy, and positive predictive value, and negative predictive value of 95.2%, 92%, 93.5%, 90.0%, and 95.8%, respectively [43]. Conventional US has a sensitivity and specificity of 81% and 91%, respectively, in the detection of full-thickness UCL tears [44]. The sensitivity and specificity of dynamic stress US for the detection of UCL injury are 96% and 81%, respectively [44]. In a review of the literature, Sutterer et al [45] found that stress US can aid in the diagnosis of medial UCL tears, with an injured elbow stress delta (change in ulnohumeral joint space with valgus stress) of 2.4 mm and a stress delta difference (side-side difference in stress delta) of 1 mm, compatible with abnormal ulnohumeral joint laxity as a result of medial UCL injury. Given the scarcity of literature with regards to lateral and medial supporting structures, more rigorous studies evaluating the usefulness of US in the acute setting are needed; however, given US accuracy in the evaluation of chronic injuries, it will likely provide clinical usefulness for assessment of acute injury.


Soft Tissue Masses

Soft Tissue Masses.  Introduction/Background A variety of benign and malignant processes may present clinically as a soft tissue mass. The behavior of a mass, whether nonaggressive, indeterminant, or aggressive, can often be discerned based on history and physical examination. However, when a benign clinical diagnosis cannot be confidently provided, further characterization of a soft tissue mass with imaging is warranted [1]. Urgent imaging requests should be sought for masses that are >5 cm in diameter, deep in location, or have shown rapid growth [2]. Modern imaging techniques allow for a detailed analysis of the morphology of a soft tissue mass as well as further insight into its biologic activity, which informs the interpreter on diagnosis and appropriate next steps in management [3,4]. The purpose of this document is to identify the most appropriate imaging study(ies) to order for the assessment of a soft tissue mass based on the most frequently encountered clinical scenarios in medical practice. The rationale for the level of appropriateness granted to each study option is also described in accordance with the current literature and the consensus opinion of the members of the ACR Appropriateness Criteria Expert Panel on Musculoskeletal Imaging. This document does not address follow-up recommendations for patients with previously diagnosed masses or the appropriate approach or techniques for the imaging-guided biopsy of known masses. The former is covered by a separate ACR Appropriateness Criteria document [4], whereas the latter requires direct communication with the clinician or orthopedic oncologist supervising and coordinating patient care. OR aMayo Clinic Florida, Jacksonville, Florida. bPanel Chair, Mayo Clinic, Jacksonville, Florida. cPanel Vice-Chair, Wake Forest University School of Medicine, Winston Salem, North Carolina. dJohns Hopkins University School of Medicine, Baltimore, Maryland. eMallinckrodt Institute of Radiology Washington University School of Medicine, Saint Louis, Missouri.


Soft Tissue Masses

Soft Tissue Masses. fNova Southeastern University, Fort Lauderdale, Florida. gDiagnostic Imaging Associates, Chesterfield, Missouri. hThe University of Texas MD Anderson Cancer Center, Houston, Texas; American Academy of Orthopaedic Surgeons. iUniversity of Virginia, Charlottesville, Virginia. jSUNY Downstate Health Sciences University, Brooklyn, New York. kDuke University School of Medicine, Durham, North Carolina; American Geriatrics Society. lThe University of Texas MD Anderson Cancer Center, Houston, Texas; Commission on Nuclear Medicine and Molecular Imaging. mBillings Clinic, Billings, Montana; American Academy of Family Physicians. nSpecialty Chair, VA San Diego Healthcare System, San Diego, California. 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 Soft Tissue Masses Discussion of Procedures by Variant Variant 1: Superficial soft tissue mass. Initial imaging. The body regions covered in this clinical scenario include the neck, chest, abdomen, pelvis, humerus/upper arm, shoulder, elbow, forearm, wrist, hand, hip, femur/thigh, knee, tibia/lower leg, ankle, and foot. US Area of Interest Ultrasound (US) has become increasingly recognized as an excellent triage tool for evaluation of superficial soft tissue masses [12-15]. This recognition has been further supported by a recent prospective study of 219 histologically proven masses that showed US had a sensitivity, specificity, positive predictive value, and negative predictive value of 93.3%, 97.9%, 45.2%, and 99.9%, respectively, for discriminating benign from malignant tumors in the superficial soft tissues [16].


Soft Tissue Masses

Soft Tissue Masses. The same group of researchers had similar results in an earlier separate retrospective analysis of 247 histologically proven masses [17]. However, although these results highlight the benefits of US in the initial assessment of superficial masses, the overall number of malignancies in both the prospective [16] and retrospective [17] studies was very small (12 patients and 11 patients, respectively). Another recent study of 42 histologically proven masses concluded that MRI performed after US does not frequently change the working diagnosis or add diagnostic value, but again, this study only included a small number of malignancies and the value of MRI for these malignancies was not separately addressed in the study [18]. Therefore, we emphasize that these studies do not have sufficient power for showing high accuracy of US in the diagnosis of malignancy. Ultimately, US is most beneficial for triage, and when US features are not clearly benign or when history and physical examination findings are otherwise concerning, further imaging is required [9,19]. US Area of Interest With IV Contrast The use of intravenous (IV) contrast during US evaluation of soft tissue tumors may add further confidence in discriminating benign from indeterminate or malignant masses [20-22]. However, there is no literature showing that the addition of contrast provides a gain in diagnostic accuracy over standard grayscale and Doppler US features in the assessment of a soft tissue mass. Therefore, the literature does not support the use of US contrast in the initial examination of a superficial soft tissue mass. MRI Area of Interest Without and With IV Contrast There is insufficient literature to support the routine use of MRI without or with IV contrast as the initial examination for a soft tissue mass. The inherent limitations of this modality, most notably in the identification of mineralization, limit its use in isolation.


Soft Tissue Masses

Soft Tissue Masses. MRI Area of Interest Without IV Contrast There is insufficient literature to support the routine use of MRI without IV contrast as the initial examination for a soft tissue mass. The inherent limitations of this modality, most notably in the identification of mineralization, limit its use in isolation. CT Area of Interest With IV Contrast CT with IV contrast does not typically play a role in the initial evaluation of a superficial soft tissue mass. Soft Tissue Masses CT Area of Interest Without and With IV Contrast CT does not typically play a role in the initial evaluation of a superficial soft tissue mass. CT Area of Interest Without IV Contrast CT does not typically play a role in the initial evaluation of a superficial soft tissue mass. FDG-PET/CT Area of Interest There is insufficient literature to support the routine use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT for the initial evaluation of a soft tissue mass. Image-Guided Biopsy Area of Interest The literature does not support the use of image-guided biopsy as the initial examination for a soft tissue mass. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and thus would not warrant biopsy. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy should be performed only after adequate imaging [24]. Image-Guided Fine Needle Aspiration Area of Interest The literature does not support the use of image-guided fine needle aspiration as the initial examination for a soft tissue mass. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and thus would not warrant fine needle aspiration.


Soft Tissue Masses

Soft Tissue Masses. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy or fine needle aspiration should be performed only after adequate imaging [24]. Variant 2: Nonsuperficial (deep) soft tissue mass. Initial imaging. The body regions covered in this clinical scenario include the neck, chest, abdomen, pelvis, humerus/upper arm, shoulder, elbow, forearm, wrist, hand, hip, femur/thigh, knee, tibia/lower leg, ankle, and foot. Radiography Area of Interest Initial imaging assessment of a suspected musculoskeletal soft tissue mass should almost invariably begin with radiographic evaluation and is advocated by ESMO-EURACAN [9]. Radiographs remain the modality best suited for the initial assessment of a suspected soft tissue mass and are the initial study of choice for orthopedic oncologists [25,26]. However, radiographs have limitations and may not reveal an abnormality when a mass is small, deep- seated, nonmineralized, or in an area with complex anatomy such as the flank, paraspinal region, groin, or deep soft tissues of the hands and feet [11]. US Area of Interest The diagnostic accuracy of US is considerably less when lesions outside the subcutaneous tissue are included. It is also less reliable for defining deep masses in large anatomical areas [27]. Although a recent prospective study of US accuracy in the characterization of 134 histologically proven deep soft tissue masses showed promising results, there were only a small number of malignancies in the study cohort, and the investigators had a high level of US expertise [28]. Therefore, US is most appropriate for superficial masses that are small (<5 cm) in size [13] but may be appropriate for deep soft tissue masses in specific settings, such as a deep mass in a thin patient.


Soft Tissue Masses

Soft Tissue Masses. US Area of Interest With IV Contrast The diagnostic accuracy of US is considerably less when lesions outside the subcutaneous tissue are included. It is also less reliable for defining deep masses in large anatomical areas [27]. Although an assessment of diagnostic accuracy of US with IV contrast in the setting of a deep soft tissue mass is not available in the current literature, there is presumably no added benefit over standard grayscale and Doppler US. Therefore, the US with IV contrast is not useful for the initial assessment of deep soft tissue masses. MRI Area of Interest Without and With IV Contrast The current radiology, orthopedic oncology, and surgical oncology literature does not support the use of MRI without and with IV as the initial examination for a soft tissue mass. MRI Area of Interest Without IV Contrast The current radiology, orthopedic oncology, and surgical oncology literature does not support the use of MRI without IV contrast as the initial examination for a soft tissue mass. Soft Tissue Masses CT Area of Interest With IV Contrast CT with IV contrast does not typically play a role in the initial evaluation of a deep soft tissue mass. However, CT can be useful in areas where the osseous anatomy is complex or obscured for the distinction of ossification from calcification and the identification of characteristic patterns of mineralization [29,30]. In anatomically complex areas where radiographs would be less sensitive, CT may be beneficial as the initial or complementary imaging modality. Fortunately, the advent of virtual noncontrast reconstruction with modern dual-source CT scanners allows for acquisition of a single postcontrast scan with reconstruction of virtual noncontrast images, which can preclude the need for a separate precontrast scan phase [31]. For myositis ossificans, CT is superior to radiography in detecting the zonal pattern of mineralization, which is essential for early diagnosis [11].


Soft Tissue Masses

Soft Tissue Masses. In addition, CT allows for differentiation of soft tissue masses based on lesion density and can delineate vascular and bone involvement [29,30]. This differentiation may be better defined by immediately repeating the scan after contrast administration. During the assessment of cortical remodeling or invasion, the character of the interface between a soft tissue mass and the adjacent osseous cortex can usually be visualized to better advantage with CT compared to radiographs. CT Area of Interest Without and With IV Contrast CT without and with IV contrast does not typically play a role in the initial evaluation of a deep soft tissue mass. However, CT can be useful in areas where the osseous anatomy is complex or obscured for the distinction of ossification from calcification and the identification of characteristic patterns of mineralization [29,30]. In anatomically complex areas where radiographs would be less sensitive, CT may be beneficial as the initial or complementary imaging modality. Fortunately, the advent of virtual noncontrast reconstruction with modern dual- source CT scanners allows for acquisition of a single postcontrast scan with reconstruction of virtual noncontrast images, which can preclude the need for a separate precontrast scan phase [31]. For myositis ossificans, CT is superior to radiography in detecting the zonal pattern of mineralization, which is essential for early diagnosis [11]. In addition, CT allows for differentiation of soft tissue masses based on lesion density and can delineate vascular and bone involvement [29,30]. This differentiation may be better defined by immediately repeating the scan after contrast administration. During the assessment of cortical remodeling or invasion, the character of the interface between a soft tissue mass and the adjacent osseous cortex can usually be visualized to better advantage with CT compared to radiographs.


Soft Tissue Masses

Soft Tissue Masses. CT Area of Interest Without IV Contrast CT without IV contrast does not typically play a role in the initial evaluation of a deep soft tissue mass. However, CT can be useful in areas where the osseous anatomy is complex or obscured for the distinction of ossification from calcification and the identification of characteristic patterns of mineralization [29,30]. In anatomically complex areas where radiographs would be less sensitive, CT may be beneficial as the initial or complementary imaging modality. Fortunately, the advent of virtual noncontrast reconstruction with modern dual-source CT scanners allows for acquisition of a single postcontrast scan with reconstruction of virtual noncontrast images, which can preclude the need for a separate precontrast scan phase [31]. For myositis ossificans, CT is superior to radiography in detecting the zonal pattern of mineralization, which is essential for early diagnosis [11]. In addition, CT allows for differentiation of soft tissue masses based on lesion density and can delineate vascular and bone involvement [29,30]. This differentiation may be better defined by immediately repeating the scan after contrast administration. During the assessment of cortical remodeling or invasion, the character of the interface between a soft tissue mass and the adjacent osseous cortex can usually be visualized to better advantage with CT compared to radiographs. FDG-PET/CT Area of Interest FDG PET/CT does not typically play a role in the initial evaluation of a soft tissue mass. The CT component associated with PET/CT is of lower resolution compared with conventional CT and is not optimal for accurate characterization of soft tissue mineralization. Image-Guided Biopsy Area of Interest The literature does not support the use of image-guided biopsy as the initial examination for a soft tissue mass.


Soft Tissue Masses

Soft Tissue Masses. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and thus would not warrant biopsy. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the Soft Tissue Masses National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy should be performed only after adequate imaging [24]. Image-Guided Fine Needle Aspiration Area of Interest The literature does not support the use of image-guided fine needle aspiration as the initial examination for a soft tissue mass. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and thus would not warrant fine needle aspiration. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy or fine needle aspiration should be performed only after adequate imaging [24]. Variant 3: Soft tissue mass. Nondiagnostic radiograph and noncontrast-enhanced ultrasound. Next imaging study. The body regions covered in this clinical scenario include the neck, chest, abdomen, pelvis, humerus/upper arm, shoulder, elbow, forearm, wrist, hand, hip, femur/thigh, knee, tibia/lower leg, ankle, and foot. Of note, this variant addresses the scenario in which radiographs and/or noncontrast US have been performed but did not sufficiently characterize a soft tissue mass. In addition, this variant presumes there are no contraindications to any imaging modality. Variant 4 specifically addresses the situation of a contraindication to MRI.


Soft Tissue Masses

Soft Tissue Masses. CT Area of Interest With IV Contrast Although CT with IV contrast lacks the specificity afforded by MRI in many cases, it does provide useful staging data [32]. In a multi-institutional study of 133 patients with primary soft tissue malignancies, Panicek et al [32] found no statistically significant difference between MRI and contrast-enhanced CT imaging in determining tumor involvement of muscle, bone, joint, or neurovascular structures. Therefore, CT with IV contrast remains an important adjunct in the evaluation of a soft tissue mass. The advent of virtual noncontrast reconstruction with modern dual-source CT scanners allows for acquisition of a single postcontrast scan with reconstruction of virtual noncontrast images, which can preclude the need for a separate precontrast scan phase [31]. Similar to CT without IV contrast [21, 22], virtual noncontrast imaging allows distinction of ossification from calcification and identification of characteristic patterns of mineralization [29,30] and is particularly useful in assessment of mass mineralization in areas where the osseous anatomy is complex or obscured and radiographs would be less sensitive. CT Area of Interest Without and With IV Contrast The advent of virtual noncontrast reconstruction with modern dual-source CT scanners allows for acquisition of a single postcontrast scan with reconstruction of virtual noncontrast images, which can preclude the need for a separate precontrast scan phase [31]. However, a traditional CT without and with IV contrast may be appropriate for characterization of mineralization in an anatomically complex area. Although a multi-institutional study of 133 patients with primary soft tissue malignancies by Panicek et al [32] found no statistically significant difference between MRI and contrast-enhanced CT imaging in determining tumor involvement of muscle, bone, joint, or neurovascular structures, this study did not specifically endorse the usefulness of dual-phase CT without and with IV contrast.


Soft Tissue Masses

Soft Tissue Masses. CT with IV contrast remains an important adjunct in the evaluation of a soft tissue mass. CT Area of Interest Without IV Contrast The literature does not support the use of single-phase CT without IV contrast as the next imaging study for the evaluation of a soft tissue mass. Although a multi-institutional study of 133 patients with primary soft tissue malignancies by Panicek et al [32] found no statistically significant difference between MRI and contrast-enhanced CT imaging in determining tumor involvement of muscle, bone, joint, or neurovascular structures, this study did not endorse the usefulness of single-phase CT without IV contrast. MRI Area of Interest Without and With IV Contrast MRI without and with IV contrast is the technique of choice as the next imaging study for the evaluation of soft tissue masses. Its improved soft tissue contrast and multiplanar capability have provided significant advantages for lesion conspicuity, intrinsic tumor characterization, and local staging [3,11]. Vascular structures and neurovascular involvement are more easily defined when compared with CT. Soft Tissue Masses The use of MR contrast agents improves the differentiation of benign from malignant soft tissue masses [33]. The contrast allows for better demarcation between viable tumor and muscle, edema-like reactive change, hemorrhage, and tumor necrosis, as well as providing information on tumor vascularity. In addition to static MR contrast imaging, there are several additional modern MR techniques that provide greater insight into the character and behavior of soft tissue masses and can assist with differentiation of benign from malignant tumors. These include diffusion-weighted imaging [34-37], dynamic contrast-enhanced perfusion imaging [38,39], and MR spectroscopy [38,39]. Of note, chemical-shift imaging has not shown utility in differentiating benign from malignant soft tissue masses [40].


Soft Tissue Masses

Soft Tissue Masses. However, the Dixon technique will likely be increasingly recognized as beneficial for soft tissue tumor imaging through its potential to provide more homogenous fat suppression when compared to traditional T2-fat saturated imaging and better resolution than inversion recovery imaging. Furthermore, it may help decrease imaging time because the Dixon water-only and fat- only images are acquired simultaneously [41,42]. MRI Area of Interest Without IV Contrast MRI without IV contrast may be beneficial as the next imaging study for the evaluation of soft tissue masses. Its improved soft tissue contrast and multiplanar capability have provided significant advantages for lesion conspicuity, intrinsic tumor characterization, and local staging [3,11]. Vascular structures and neurovascular involvement are more easily defined when compared with CT. The use of MR contrast agents improves the differentiation of benign from malignant soft tissue masses [33]. The contrast allows for better demarcation between viable tumor and muscle, edema-like reactive change, hemorrhage, and tumor necrosis, as well as providing information on tumor vascularity. In addition to static MR contrast imaging, there are several additional modern MR techniques that provide greater insight into the character and behavior of soft tissue masses and can assist with differentiation of benign from malignant tumors. These include diffusion-weighted imaging [34-37], dynamic contrast-enhanced perfusion imaging [38,39], and MR spectroscopy [38,39]. Of note, chemical-shift imaging has not shown utility in differentiating benign from malignant soft tissue masses [40]. However, the Dixon technique will likely be increasingly recognized as beneficial for soft tissue tumor imaging through its potential to provide more homogenous fat suppression when compared to traditional T2-fat saturated imaging and better resolution than inversion recovery imaging.


Soft Tissue Masses

Soft Tissue Masses. Furthermore, it may help decrease imaging time because the Dixon water-only and fat- only images are acquired simultaneously [41,42]. FDG-PET/CT Area of Interest As a general rule, PET/CT imaging maximum standard uptake value can be useful for differentiating between benign and malignant musculoskeletal masses. When combined with anatomic data provided by CT, FDG-PET/CT can be useful in distinguishing aggressive soft tissue tumors from benign lesions [43-45]. Benz et al [46] showed that FDG-PET can be used to determine a tumor glycolytic phenotype in sarcomas, which correlates significantly with histologic grade. Fused FDG-PET/CT images can be used to plan biopsy, targeting areas with more metabolic activity that may give higher diagnostic yield. Furthermore, a meta-analysis found that FDG-PET can be a helpful tool for predicting outcome in patients with soft tissue sarcoma [47]. Lastly, FDG-PET/CT is an excellent modality to detect metastatic disease and assess treatment response [48]. Despite these benefits, FDG-PET/CT does not usually play a role as the next imaging study for the characterization of a soft tissue mass when initial radiographs or US are nondiagnostic. Image-Guided Biopsy Area of Interest The literature does not support the use of image-guided biopsy as the next step in evaluation following nondiagnostic radiographs or US of a soft tissue mass. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and thus would not warrant biopsy. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy should be performed only after adequate imaging [24].


Soft Tissue Masses

Soft Tissue Masses. Image-Guided Fine Needle Aspiration Area of Interest The literature does not support the use of image-guided fine needle aspiration as the next step in evaluation following nondiagnostic radiographs or US of a soft tissue mass. At least 20% to 25% of soft tissue masses can demonstrate features that allow for confident diagnosis based on MRI alone [23], many of which are benign and Soft Tissue Masses thus would not warrant biopsy. Therefore, diagnostic imaging that includes comprehensive characterization of the mass should routinely be performed before biopsy. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy should be performed only after adequate imaging [24]. US Area of Interest With IV Contrast Although prospective studies have emerged suggesting that US is accurate in the discrimination of benign from malignant soft tissue masses, the number of malignancies in these studies was limited [16,28]. Therefore, the use of US for the final evaluation and staging of a deep soft tissue mass is not recommended. Variant 4: Soft tissue mass. Nondiagnostic radiograph and noncontrast-enhanced ultrasound. MRI contraindicated. Next imaging study. The body regions covered in this clinical scenario include the neck, chest, abdomen, pelvis, humerus/upper arm, shoulder, elbow, forearm, wrist, hand, hip, femur/thigh, knee, tibia/lower leg, ankle, and foot. CT Area of Interest With IV Contrast CT has become a useful technique for the evaluation of patients who cannot undergo MRI and is the modality of choice in this scenario [29]. In the evaluation of suspected tumors, contrast imaging is especially useful in distinguishing vascularized from potentially necrotic regions of the tumor. With modern CT technology, calcification can usually be distinguished from vascular enhancement. Of note, dual-energy CT is a relatively newer technology that has shown utility in evaluation of soft tissue masses.


Soft Tissue Masses

Soft Tissue Masses. Using the differences in energy attenuation of soft tissue at 80 kVp and 140 kVp, this technique can allow reconstruction of virtual noncontrast CT images as well as significantly reduce metal artifact in the assessment of metal implants, improving the diagnostic value of imaging in the surrounding soft tissues [49,50]. It has also shown application in the assessment of marrow edema [51,52] and has been investigated in the distinction of marrow edema from intramedullary tumor invasion [53]. Furthermore, spectral CT is emerging as a useful tool for distinguishing benign from malignant soft tissue masses [54]. CT Area of Interest Without and With IV Contrast Dual-phase CT without and with IV contrast as the next imaging study for the evaluation of a soft tissue mass may be appropriate when MRI is contraindicated. Although single-phase CT with IV contrast is considered most appropriate in this clinical scenario given the advent of virtual noncontrast reconstruction with modern dual-source CT scanners [31], a traditional CT without and with IV contrast can be helpful for characterization of mineralization in an anatomically complex area. CT Area of Interest Without IV Contrast The literature does not support the use of a single-phase CT without IV contrast as the next imaging study for the evaluation of a soft tissue mass when MRI is contraindicated. However, single-phase CT with IV contrast is a useful technique for the evaluation of patients who cannot undergo MRI and is the modality of choice in this scenario [29]. In the evaluation of suspected tumors, contrast imaging is especially useful in distinguishing vascularized from potentially necrotic regions of the tumor. With modern CT technology, calcification can usually be distinguished from vascular enhancement. Therefore, CT without IV contrast is usually not beneficial.


Soft Tissue Masses

Soft Tissue Masses. FDG-PET/CT Area of Interest Although FDG-PET/CT is not typically used as the next imaging study for the characterization of a soft tissue mass, PET/CT imaging maximum standard uptake value can be useful for differentiating between benign and malignant musculoskeletal masses. When combined with anatomic data provided by CT, FDG-PET/CT can be useful in distinguishing aggressive soft tissue tumors from benign lesions [43-45]. Benz et al [46] showed that FDG-PET can be used to determine a tumor glycolytic phenotype in sarcomas, which correlates significantly with histologic grade. Fused FDG-PET/CT images can be used to plan biopsy, targeting areas with more metabolic activity that may give higher diagnostic yield. Furthermore, a meta-analysis found that FDG-PET can be a helpful tool for predicting outcome in patients with soft tissue sarcoma [47]. Lastly, FDG-PET/CT is an excellent modality to detect metastatic disease and assess treatment response [48]. Despite these benefits, FDG-PET/CT does not usually play a role in the initial assessment of a soft tissue mass. Image-Guided Biopsy Area of Interest The literature does not support the use of image-guided biopsy as the next step in evaluation following nondiagnostic radiographs or US of a soft tissue mass. If MRI is contraindicated, characterization of the mass using Soft Tissue Masses CT with IV contrast should routinely be performed before biopsy [29]. In fact, the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology for Soft Tissue Sarcoma state that biopsy should be performed only after adequate imaging [24]. Image-Guided Fine Needle Aspiration Area of Interest The literature does not support the use of image-guided fine needle aspiration as the next step in evaluation following nondiagnostic radiographs or US of a soft tissue mass. If MRI is contraindicated, characterization of the mass using CT with IV contrast should routinely be performed before biopsy [29].