The Role of Imaging for GI Bleeding: ACG and SAR Consensus Recommendations.

Gastrointestinal (GI) bleeding is the most common GI diagnosis leading to hospitalization within the United States. Prompt diagnosis and treatment of GI bleeding is critical to improving patient outcomes and reducing high health care utilization and costs. Radiologic techniques including CT angiography, catheter angiography, CT enterography, MR enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan) are frequently used to evaluate patients with GI bleeding and are complementary to GI endoscopy. However, multiple management guidelines exist, which differ in the recommended utilization of these radiologic examinations. This variability can lead to confusion as to how these tests should be used in the evaluation of GI bleeding. In this document, a panel of experts from the American College of Gastroenterology and Society of Abdominal Radiology provide a review of the radiologic examinations used to evaluate for GI bleeding including nomenclature, technique, performance, advantages, and limitations. A comparison of advantages and limitations relative to endoscopic examinations is also included. Finally, consensus statements and recommendations on technical parameters and utilization of radiologic techniques for GI bleeding are provided. © Radiological Society of North America and the American College of Gastroenterology, 2024. Supplemental material is available for this article. This article is being published concurrently in American Journal of Gastroenterology and Radiology. The articles are identical except for minor stylistic and spelling differences in keeping with each journal's style. Citations from either journal can be used when citing this article. See also the editorial by Lockhart in this issue.

Dual-Energy CT Evaluation of Gastrointestinal Bleeding.

Gastrointestinal (GI) bleeding is a potentially life-threatening condition accounting for more than 300 000 annual hospitalizations. Multidetector abdominopelvic CT angiography is commonly used in the evaluation of patients with GI bleeding. Given that many patients with severe overt GI bleeding are unlikely to tolerate bowel preparation, and inpatient colonoscopy is frequently limited by suboptimal preparation obscuring mucosal visibility, CT angiography is recommended as a first-line diagnostic test in patients with severe hematochezia to localize a source of bleeding. Assessment of these patients with conventional single-energy CT systems typically requires the performance of a noncontrast series followed by imaging during multiple postcontrast phases. Dual-energy CT (DECT) offers several potential advantages for performing these examinations. DECT may eliminate the need for a noncontrast acquisition by allowing the creation of virtual noncontrast (VNC) images from contrast-enhanced data, affording significant radiation dose reduction while maintaining diagnostic accuracy. VNC images can help radiologists to differentiate active bleeding, hyperattenuating enteric contents, hematomas, and enhancing masses. Additional postprocessing techniques such as low-kiloelectron voltage virtual monoenergetic images, iodine maps, and iodine overlay images can increase the conspicuity of contrast material extravasation and improve the visibility of subtle causes of GI bleeding, thereby increasing diagnostic confidence and assisting with problem solving. GI bleeding can also be diagnosed with routine single-phase DECT scans by constructing VNC images and iodine maps. Radiologists should also be aware of the potential pitfalls and limitations of DECT. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.

Review of CT-guided trans-osseous biopsies.

Percutaneous image-guided biopsy is an invaluable technique in the management of a myriad of different conditions; however, percutaneous access to some targets remains challenging. Trans-osseous biopsy provides safe, high-yield access to many challenging lesions in the chest, abdomen, and pelvis which might otherwise require more invasive procedures, such as mediastinoscopy or surgery to establish a histological diagnosis. Additionally, trans-osseous biopsy is well tolerated and may reduce the risk of injury to intervening vital structures as compared to other percutaneous techniques. In this article we review the indications, technical challenges, alternative techniques, and potential complications of trans-sternal, trans-costal, trans-scapular, trans-vertebral, trans-iliac, and trans-sacral biopsies.

Management of gastrointestinal bleeding: Society of Abdominal Radiology (SAR) Institutional Survey.

Despite guidelines developed to standardize the diagnosis and management of gastrointestinal (GI) bleeding, significant variability remains in recommendations and practice. The purpose of this survey was to obtain information on practice patterns for the evaluation of overt lower GI bleeding (LGIB) and suspected small bowel bleeding. A 34-question electronic survey was sent to all Society of Abdominal Radiology (SAR) members. Responses were received from 52 unique institutions (40 from the United States). Only 26 (50%) utilize LGIB management guidelines. 32 (62%) use CT angiography (CTA) for initial evaluation in unstable patients. In stable patients with suspected LGIB, CTA is the preferred initial exam at 21 (40%) versus colonoscopy at 24 (46%) institutions. CTA use increases after hours for both unstable (n = 32 vs. 35, 62% vs. 67%) and stable patients (n = 21 vs. 27, 40% vs 52%). CTA is required before conventional angiography for stable (n = 36, 69%) and unstable (n = 15, 29%) patients. 38 (73%) institutions obtain two post-contrast phases for CTA. 49 (94%) institutions perform CT enterography (CTE) for occult small bowel bleeding with capsule endoscopy (n = 26, 50%) and CTE (n = 21, 40%) being the initial test performed. 35 (67%) institutions perform multiphase CTE for occult small bowel bleeding. In summary, stable and unstable patients with overt lower GI are frequently imaged with CTA, while CTE is frequently performed for suspected occult small bowel bleeding.

Gastrointestinal Bleeding at CT Angiography and CT Enterography: Imaging Atlas and Glossary of Terms.

Gastrointestinal (GI) bleeding is a common potentially life-threatening medical condition frequently requiring multidisciplinary collaboration to reach the proper diagnosis and guide management. GI bleeding can be overt (eg, visible hemorrhage such as hematemesis, hematochezia, or melena) or occult (eg, positive fecal occult blood test or iron deficiency anemia). Upper GI bleeding, which originates proximal to the ligament of Treitz, is more common than lower GI bleeding, which arises distal to the ligament of Treitz. Small bowel bleeding accounts for 5-10% of GI bleeding cases commonly manifesting as obscure GI bleeding, where the source remains unknown after complete GI tract endoscopic and imaging evaluation. CT can aid in identifying the location and cause of bleeding and is an important complementary tool to endoscopy, nuclear medicine, and angiography in evaluating patients with GI bleeding. For radiologists, interpreting CT scans in patients with GI bleeding can be challenging owing to the large number of images and the diverse potential causes of bleeding. The purpose of this pictorial review by the Society of Abdominal Radiology GI Bleeding Disease-Focused Panel is to provide a practical resource for radiologists interpreting GI bleeding CT studies that reviews the proper GI bleeding terminology, the most common causes of GI bleeding, key patient history and risk factors, the optimal CT imaging technique, and guidelines for case interpretation and illustrates many common causes of GI bleeding. A CT reporting template is included to help generate radiology reports that can add value to patient care. An invited commentary by Al Hawary is available online. Online supplemental material is available for this article. ©RSNA, 2021.

MRE Evaluation of Intestinal Inflammation: Qualitative and Quantitative Assessment.

ABSTRACT: Magnetic resonance enterography (MRE) is a powerful tool for evaluation and management of patients with Crohn disease. Changes of active inflammation of the small bowel can reliably and reproducibly be detected and monitored. Findings indicative of active inflammation include bowel wall thickening, intramural edema and mural hyperenhancement. These changes are most commonly reported qualitatively; however, quantitative indices have also been developed and validated to measure and monitor inflammation both for clinical care and research purposes. This article describes the essential findings of active inflammation on MRE as well as the fundamentals of both qualitative and quantitative assessment and reporting.

CT-guided biopsy of pulmonary nodules ≤10 mm: Diagnostic yield based on nodules' lobar and segmental distribution.

PURPOSE: The aim of our study is to evaluate the diagnostic performance of CT-guided biopsy of lung nodules ≤10 mm based on their lobar and segmental location. MATERIALS AND METHODS: This was a retrospective study performed on 193 CT-guided percutaneous transthoracic needle biopsies of lung nodules ≤10 mm in greatest dimension, between January 1, 2013 and April 30, 2019. Biopsies were classified as either diagnostic or non-diagnostic based on final cytology and surgical pathology reports. Diagnostic results were those that met parameters for malignancy or a specific benign diagnosis, whereas atypical cells, non-specific benignity, or insufficient specimen were considered non-diagnostic. RESULTS: A total of 1577 CT-guided percutaneous transthoracic needle biopsies were reviewed. Of these, 193 nodules (12.24%) measured ≤10 mm and were selected for further analysis. Of the 193 biopsies, 138 yielded diagnostic results while 56 yielded nondiagnostic results (71% vs 29%, respectively). When analyzed by nodule location, the superior segments of the lower lobes boasted the highest diagnostic yield compared to nodules located in the basal segments of the lower lobes which had the lowest diagnostic yield (84.2% vs 64.7%, respectively). Nodules in the upper lobes and in the middle lobes had a diagnostic yield of 70% and 66.7%, respectively. CONCLUSION: The diagnostic performance of CT-guided biopsy of lung nodules ≤10 mm in diameter may be affected by lobar and segmental location. While the overall performance was good (diagnostic yield of 71%), the yield varied nearly 20% depending on location.

Computed tomography and magnetic resonance enterography protocols and techniques: survey of the Society of Abdominal Radiology Crohn's Disease Disease-Focused Panel.

PURPOSE: To survey Society of Abdominal Radiology Crohn's Disease (CD) Disease-Focused Panel (DFP) members to understand state-of-the-art CT/MR enterography (CTE/MRE) protocols and variability between institutions. METHODS: This study was determined by an institutional review board to be "exempt" research. The survey consisted of 70 questions about CTE/MRE patient preparation, administration of contrast materials, imaging techniques, and other protocol details. The survey was administered to DFP members using SurveyMonkey® (Surveymonkey.com). Descriptive statistical analyses were performed. RESULTS: Responses were received from 16 DFP institutions (3 non-USA, 2 pediatric); 15 (94%) were academic/university-based. 10 (63%) Institutions image most CD patients with MRE; 4 (25%) use CTE and MRE equally. Hypoperistaltic medication is given for MRE at 13 (81%) institutions versus only 2 (13%) institutions for CTE. Most institutions have a technologist or nurse monitor oral contrast material drinking (n = 12 for CTE, 75%; n = 11 for MRE, 69%). 2 (13%) institutions use only dual-energy capable scanners for CTE, while 9 (56%) use either a single-energy or dual-energy scanner based on availability. Axial CTE images are reconstructed at 2-3 mm thickness at 8 (50%) institutions, > 3 mm at 5 (31%), and < 2 mm at 3 (19%) institutions. 13 (81%) institutions perform MRE on either 1.5 or 3T scanners without preference. All institutions perform MRE multiphase postcontrast imaging (median = 4 phases), ranging from 20 to 600 s after contrast material injection. CONCLUSION: CTE and MRE protocol knowledge from DFP institutions can help radiology practices optimize/standardize protocols, potentially improving image quality and patient outcomes, permitting objective comparisons between examinations, and facilitating research.

Small Bowel Crohn Disease at CT and MR Enterography: Imaging Atlas and Glossary of Terms.

Representatives from the Society of Abdominal Radiology Crohn's Disease-Focused Panel, the Society for Pediatric Radiology, the American Gastroenterological Association, and other international experts recently reported consensus recommendations for standardized nomenclature for the interpretation and reporting of CT enterography and MR enterography findings of small bowel Crohn disease. The consensus recommendations included CT enterography and MR enterography bowel wall findings that are associated with Crohn disease, findings that occur with penetrating Crohn disease, and changes that occur in the mesentery related to Crohn disease. Also included were recommended radiology report impression statements that summarize the findings of small bowel Crohn disease at CT enterography and MR enterography. This article, authored by the Society of Abdominal Radiology Crohn's Disease-Focused Panel, illustrates the imaging findings and recommended radiology report impression statements described in the consensus recommendations with examples of CT enterography and MR enterography images. Additional interpretation guidelines for reporting CT enterography and MR enterography examinations are also presented. The recommended standardized nomenclature can be used to generate radiology report dictations that will help guide medical and surgical management for patients with small bowel Crohn disease. Online supplemental material is available for this article. ©RSNA, 2020See discussion on this article by Heverhagen.

Society of abdominal radiology gastrointestinal bleeding disease-focused panel consensus recommendations for CTA technical parameters in the evaluation of acute overt gastrointestinal bleeding.

PURPOSE: To formulate consensus recommendations for CT angiography technical parameters used to evaluate overt gastrointestinal (GI) bleeding. METHODS: An electronic questionnaire consisting of 17 questions was sent to a panel of 16 radiologists with expertise on the imaging of GI bleeding from the Society of Abdominal Radiology GI Bleeding disease-focused panel to obtain consensus agreement on issues related to CTA technical parameters for imaging overt GI bleeding. A multi-round Delphi method of voting was performed to obtain consensus which was defined as ≥ 80% agreement. RESULTS: Consensus agreement was reached in 15/17 (89%) of the questions including the technique for the administration of IV contrast, the number of phases, scan timing, and image reconstruction. CONCLUSIONS: A panel of experts on the imaging of GI bleeding from the Society of Abdominal Radiology was able to reach consensus on the majority of technical parameters used for CTA of overt GI bleeding. These recommendations should improve the quality of patient care by adopting these minimal technical requirements for optimal exam performance and lead to less variation in the performance of these exams which will facilitate collecting and comparing published data from different centers. These recommendations will need revisions as additional scientific data become available.

Image-Guided Cholecystostomy Tube Placement: Short- and Long-Term Outcomes of Transhepatic Versus Transperitoneal Placement.

OBJECTIVE: Image-guided percutaneous cholecystostomy may be performed by a transhepatic or transperitoneal approach. We compared the short- and long-term outcomes of percutaneous cholecystostomy related to route of catheter placement. MATERIALS AND METHODS: A retrospective observational study of image-guided percutaneous cholecystostomy was performed from 2004 to 2016. A search of the hospital's radiology information service was performed using the keywords "percutaneous cholecystostomy," "gallbladder drain," and "cholecystostomy tube" and the relevant Current Procedural Terminology codes. All search results were reviewed to identify the cohort of 373 patients who underwent initial percutaneous cholecystostomy catheter placement. Imaging was reviewed to determine the method and route of percutaneous cholecystostomy and complications. A chart review was performed to determine clinical outcomes. Differences were examined using a generalized linear model assuming a binary distribution and logit function. RESULTS: Percutaneous cholecystostomy catheter placement was performed using ultrasound guidance alone in 229 patients, ultrasound access with fluoroscopic guidance in 129 patients, CT guidance in 14 patients, and fluoroscopic guidance in one patient. The trocar technique was used for 183 patients, and the Seldinger technique was used for 190 patients. Two hundred eighteen percutaneous cholecystostomy catheters were placed via the transhepatic route, and 153 were placed via the transperitoneal route. The most common catheter sizes used were 8.5 French (n = 234) and 10 French (n = 124). No significant differences were observed between transperitoneal and transhepatic placement with regard to the frequency of pain, clogging, skin infection, bleeding, biloma, cholangitis, leakage, abscess, unplanned catheter removal, or need for replacement (p > 0.05). CONCLUSION: No evidence of a difference in outcomes was observed for transhepatic cholecystostomy tube placement over transperitoneal placement. The route that appears safer and less technically challenging should therefore be chosen.

Risk factors for radiation exposure in newly diagnosed IBD patients.

PURPOSE: Patients with inflammatory bowel disease (IBD) may be exposed to high doses of diagnostic radiation. The purpose of this study is to identify subsets of this population at risk for significant radiation exposure. METHODS: This HIPAA compliant, IRB approved study consists of 336 patients (237 adult and 99 pediatric) within the Ocean State Crohn's & Colitis Area Registry (OSCCAR). All were newly diagnosed with IBD and prospectively enrolled between 1/2008 and 12/2012. Comprehensive chart review was performed. RESULTS: 207 (61.6%) patients were diagnosed with Crohn's disease (CD), 120 (35.7%) with ulcerative colitis (UC), and 9 (2.7%) with inflammatory bowel disease, type unspecified (IBDU). 192 (57.1%) patients were exposed to GI-specific radiation. Average GI-specific radiation dose for adult IBD patients was 14.1 mSV and was significantly greater among adult CD than adult UC patients (p = 0.01). Pediatric patients underwent fewer CT scans (p < 0.0001). Risk factors for increased radiation exposure include: GI surgery (p = 0.003), biologic therapy (p = 0.01), pain-predominant symptoms (as compared to diarrhea-predominant symptoms; p < 0.05), and isolated ileal disease (p = 0.02). Patients with stricturing or penetrating disease received higher radiation doses than patients with non-stricturing, non-penetrating disease (p < 0.0001). CONCLUSIONS: A variety of risk factors are associated with increased exposure to ionizing radiation after diagnosis of IBD. Knowledge of these risk factors can help physicians prospectively identify patients at risk for elevated radiation exposure and consider low-dose or radiation-free imaging.

MR enterography in Crohn's disease: current consensus on optimal imaging technique and future advances from the SAR Crohn's disease-focused panel.

MR enterography is a powerful tool for the non-invasive evaluation of patients with Crohn's disease (CD) without ionizing radiation. The following paper describes the current consensus on optimal imaging technique, interpretation, and future advances from the Society of Abdominal Radiology CD-focused panel.

Identification of Nonalcoholic Fatty Liver Disease following Pancreatic Surgery in a Western Cohort Using a Novel Radiographic Technique.

BACKGROUND AND AIMS: While traditional risk factors for the development of nonalcoholic fatty liver disease (NAFLD) relate to metabolic syndrome, several Asian studies have suggested a high rate of de novo NAFLD following pancreaticoduodenectomy (PD). The aim of this study is to identify de novo NAFLD after pancreatic surgery and its associated risk factors. METHODS: A retrospective cohort of patients at a single center that underwent PD or distal pancreatectomy (DP) over 7 years was identified. Pre- and postoperative contrast-enhanced computed tomography scans of the abdomen were reviewed, including attenuation measurements of the liver, spleen, and muscle. Primary outcomes included hepatic attenuation, liver to muscle ratio (LMR), and liver to spleen ratio (LSR). RESULTS: Of the 96 patients (mean age 64.3) included, 70% underwent PD, and 30% underwent DP. The mean LMR decreased significantly from 1.81 to 1.66 (p=0.02), noted only in men. No interaction effect with LMR was observed with surgical type, chemotherapy, blood loss, pancreatic enzyme replacement, or transaminases. LMR decreased in 55% of subjects. CONCLUSIONS: Increased fatty infiltration, as evidence by decreased LMR, was found among men that underwent PD and DP within a year of surgery. This may be related to weight loss and malabsorption and deserves further investigation.

Resident experience increases diagnostic rate of thyroid fine-needle aspiration biopsies.

RATIONALE AND OBJECTIVES: The aim of this study was to determine whether the diagnostic yield of thyroid fine-needle aspirations (FNAs) changes over the course of residency training. MATERIALS AND METHODS: We identified 5418 ultrasound-guided thyroid nodule FNAs performed in our radiology department from 2004 through 2012. For each FNA, we recorded if the FNA was performed by a resident and if so the name of the resident and supervising attending radiologist. For each resident, we determined the level of training based on their graduation year from our residency program and the date of the FNA as well as prior surgical training and if they completed subsequent interventional radiology fellowship. Pathology reports were reviewed, and FNAs were classified as diagnostic or nondiagnostic (ND). Generalized mixed models were used to assess ND rate with postgraduate years, including residents with and without prior surgical training or if they subsequently completed an interventional radiology fellowship. RESULTS: Of the 5418 thyroid FNAs, 3164 (58.4%) were performed by a radiology resident under the direct supervision of an attending physician. There was a significant decrease in ND rate as postgraduate years increased (P < .05). A significant decrease in ND rate was found as postgraduate years increased for residents without prior surgical training (P = .0007) or subsequent training in interventional radiology (P = .0014); however, no significant decrease was found for residents with surgical training (P = .37) or completing an interventional radiology fellowship (P = .08). In addition, no significant difference was found for ND rate between postgraduate year 4 (PGY4) and PGY5 (P > .05). CONCLUSIONS: ND thyroid FNA rates progressively decrease with training level, suggesting that early and continued participation in procedures throughout residency improves outcomes. This is particularly true for residents without prior surgical training or subsequent interventional radiology fellowship.

Gastric band slippage: a case-controlled study comparing new and old radiographic signs of this important surgical complication.

OBJECTIVE: The purpose of this study was to compare the diagnostic performance of four radiographic signs of gastric band slippage: abnormal phi angle, the "O sign," inferior displacement of the superolateral gastric band margin, and presence of an air-fluid level above the gastric band. MATERIALS AND METHODS: A search of the electronic medical record identified 21 patients with a surgically proven slipped gastric band and 63 randomly-selected asymptomatic gastric band patients who had undergone barium swallow studies. These studies were evaluated for the four signs of band slippage by two independent radiologists who were blinded to clinical data. Sensitivity, specificity, and positive and negative predictive values were calculated for each radiographic sign of band slippage. Interobserver agreement between radiologists was assessed using the Fleiss kappa statistic. RESULTS: In evaluating for gastric band slippage, an abnormal phi angle greater than 58° was 91-95% sensitive and 52-62% specific (κ = 0.78), the O sign was 33-48% sensitive but 97% specific (κ = 0.84), inferior displacement of the superolateral band margin by more than 2.4 cm from the diaphragm was 95% sensitive and 97-98% specific (κ = 0.97), and the presence of an air-fluid level was 95% sensitive and 100% specific (κ = 1.00). CONCLUSION: We report two previously undescribed radiographic signs of gastric band slippage that are both sensitive and specific for this important surgical complication and recommend that these signs should be incorporated into the imaging evaluation of gastric band patients.

Management of nodules with initially nondiagnostic results of thyroid fine-needle aspiration: can we avoid repeat biopsy?

PURPOSE: To identify demographic and ultrasonographic (US) features associated with malignancy after initially nondiagnostic results of fine-needle aspiration (FNA) to help clarify the role of repeat FNA, surgical excision, or serial US in these nodules. MATERIALS AND METHODS: This study was HIPAA compliant and institutional review board approved; informed consent was waived. Thyroid nodules (n = 5349) that underwent US-guided FNA in 2004-2012 were identified; 393 were single nodules with nondiagnostic FNA results but adequate cytologic, surgical, or US follow-up. Demographic information and diameters and volume at US at first biopsy were modeled with malignancy as outcome through medical record review. Exact logistic regression was used to model malignancy outcomes, demographic comparisons with age were made (Student t test, Satterthwaite test), and proportion confidence intervals (CIs) were estimated (Clopper-Pearson method). RESULTS: Of 393 nodules with initially nondiagnostic results, nine malignancies (2.3%) were subsequently diagnosed with repeat FNA (n = 2, 0.5%) or surgical pathologic examination (n = 7, 1.8%), 330 (84.0%) were benign, and 54 (13.7%) were stable or decreased in size at serial US (mean follow-up, 3.0 years; median, 2.5 years; range, 1.0-7.8 years). Patients with malignancies were significantly older (mean age, 62.7 years; median, 64 years; range, 47-77 years) than those without (mean age, 55.4 years; median, 57 years; range, 12-94 years; P = .0392). Odds of malignancy were 4.2 times higher for men versus women (P = .045) and increased significantly for each 1-cm increase in anteroposterior, minimum, and mean nodule diameter (1.78, 2.10, and 1.96, respectively). In 393 nodules, no malignancies were detected in cystic or spongiform nodules (both, n = 11, 2.8%; 95% CI: 1.4%, 5.0%), nodules with eggshell calcifications (n = 9, 2.3%; 95% CI: 1.1%, 4.3%), or indeterminate echogenic foci (n = 39, 9.9%; 95% CI: 7.2%, 13.3%). CONCLUSION: Very few malignancies were diagnosed with repeat FNA following nondiagnostic FNA results (two of 336, 0.6%); therefore, clinical and US follow-up may be more appropriate than repeat FNA following nondiagnostic biopsy results.

Percutaneous ablation for small renal masses-imaging follow-up.

Image-guided percutaneous thermal ablation is a safe and effective nephron-sparing alternative to surgical resection for the treatment of small renal tumors. Assessment of treatment efficacy relies heavily on interval follow-up imaging after treatment. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) both play a pivotal role in evaluating the treatment zone, identifying residual tumor, and detecting early and delayed procedure-related complications. This article discusses a surveillance imaging protocol for patients who undergo percutaneous thermal ablation of renal tumors, and also illustrates the typical appearances of both successfully treated tumors and residual disease on contrast-enhanced CT or MRI. In addition, it discusses the imaging appearance of potential early and delayed treatment-related complications to facilitate their prompt detection and management.

Ovarian torsion: Case-control study comparing the sensitivity and specificity of ultrasonography and computed tomography for diagnosis in the emergency department.

OBJECTIVE: Evaluate the sensitivity and specificity of pelvic ultrasound (US) and abdominopelvic computed tomography (CT) for the identification of ovarian torsion in women presenting to the emergency department with acute lower abdominal or pelvic pain. MATERIALS AND METHODS: This is a retrospective study of 20 cases of ovarian torsion and 20 control patients, all of whom had both US and CT performed in the emergency department. Two radiologists who were blinded to clinical data interpreted all studies as (1) demonstrating an abnormal ovary or not, and (2) suggestive of torsion or not. Sensitivity, specificity and interobserver variation were calculated for each imaging modality. RESULTS: Pelvic US was interpreted as demonstrating an abnormal ovary in 90.0% of ovarian torsion cases by reader 1, and in 100.0% by reader 2, whereas CT was interpreted as revealing an abnormal ovary in 100.0% of torsion cases by both readers. Pelvic US for ovarian torsion was 80.0% sensitive (95% CI, 58.4-91.9%) and 95.0% specific (95% CI, 76.4-99.1%) for reader 1, while 80.0% sensitive (95% CI, 58.4-91.9%) and 85.0% specific (95% CI, 64.0-95.0%) for reader 2. Interobserver agreement for pelvic US was fair (Kappa=0.60). Abdominopelvic CT for ovarian torsion was 100.0% sensitive (95% CI, 83.9-100.0%) and 85.0% specific (95% CI, 64.0-94.5%) for reader 1, while 90.0% sensitive (95% CI, 69.9-97.2%) and 90.0% specific (95% CI, 69.9-97.2%) for reader 2. Interobserver agreement was excellent (Kappa=0.85). CONCLUSION: The diagnostic performance of CT is not shown to be significantly different from that of US in identifying ovarian torsion in this study. These results suggest that when CT demonstrates findings of ovarian torsion, the performance of another imaging exam (i.e. US) that delays therapy is unlikely to improve preoperative diagnostic yield.