Imaging of the Urachus: Anomalies, Complications, and Mimics.

Urachal anomalies are more common than previously thought, with more cases discovered incidentally, because of the increased use of cross-sectional imaging. Although an abnormal persistence of an embryologic communication between the bladder and the umbilicus is often recognized and managed in childhood, it may persist into adulthood, with a greater risk of morbidity. Congenital urachal anomalies that are detected early can benefit from an optimized management including surgical approach with a complete resection of the urachal remnant in cases when spontaneous resolution or medical management has failed. At imaging, the different types of urachal anomalies have a distinct appearance. A patent urachus is recognized as an elongated patent connection between the bladder and the umbilicus. An umbilical-urachal sinus is depicted as a blind focal dilatation at the umbilical end, whereas a vesicourachal diverticulum is a focal outpouching at the vesical end. Urachal cysts are visualized as midline fluid-filled sacs most frequently located near the bladder dome. Complications of urachal anomalies have nonspecific clinical findings and can mimic other abdominal and pelvic processes. Potential complications, such as infection and tumors, should be recognized early to ensure optimal management. Understanding of the embryonic development of the urachus is necessary for the radiologist to diagnose the wide variety of urachal disease. ©RSNA, 2016.

Chemical Shift MR Imaging of the Adrenal Gland: Principles, Pitfalls, and Applications.

Adrenal lesions are a common imaging finding. The vast majority of adrenal lesions are adenomas, which contain intracytoplasmic (microscopic) fat. It is important to distinguish between adenomas and malignant tumors, and chemical shift magnetic resonance (MR) imaging can be used to accomplish this distinction by depicting the fat in adenomas. Chemical shift imaging is based on the difference in precession frequencies of water and fat molecules, which causes them to be in different relative phases during the acquisition sequence and allows in-phase and opposed-phase images to be obtained. It is important to acquire these images by using the earliest possible echo times, with the opposed-phase echo before the in-phase echo, and by using a single breath hold to preserve diagnostic accuracy. Intracytoplasmic fat is depicted as signal drop on opposed-phase images when compared with in-phase images. Both qualitative and quantitative methods for assessing signal drop are detailed. The appearances of adrenal adenomas and other adrenal tumors on chemical shift MR images are described, and discriminatory ability at chemical shift MR imaging compared with that at adrenal computed tomography (CT) is explained. Other adrenal-related conditions in which chemical shift MR imaging is helpful are also discussed. Chemical shift MR imaging is a robust tool for evaluating adrenal lesions that are indeterminate at nonenhanced CT. However, it is important to know the advantages and disadvantages, including several potential imaging pitfalls. The characterization of adrenal lesions by using chemical shift MR imaging and adrenal CT should always occur in the appropriate clinical setting.

Pulmonary Hypertension: A Nomogram Based on CT Pulmonary Angiographic Data for Prediction in Patients without Pulmonary Embolism.

PURPOSE: To use cardiovascular data from computerized tomographic (CT) pulmonary angiography for facilitating the identification of pulmonary hypertension (PH) in patients without acute pulmonary embolism. MATERIALS AND METHODS: The institutional human research committee approved this retrospective study; informed consent was waived. Patients without pulmonary embolism who underwent CT pulmonary angiography and echocardiography within 24 hours of each other between December 2008 and October 2012 were retrospectively identified. The diameters of the pulmonary artery, aorta, and right and left ventricles and the severity of reflux of contrast material were assessed. The volumes of each cardiac compartment were calculated. Doppler echocardiography served as a reference standard for PH. A prediction model for PH was built by using backward logistic regression and was presented on a nomogram. The prediction model was evaluated with 10-fold cross-validation, and a test group of patients was studied between November 2012 and June 2014. RESULTS: The final study group included 182 patients, of whom 98 (54%) were given a diagnosis of PH on the basis echocardiographic results. Age of 67 years or older (odds ratio [OR] = 4.46), reflux grade of 3 or higher (OR = 2.63), right atrial volume of greater than or equal to 106 cm(3) (OR = 3.59), pulmonary artery diameter greater than or equal to 28 mm (OR = 2.52) and pulmonary artery diameter to aorta diameter ratio of greater than or equal to 0.86 (OR = 2.17) were independently associated with PH. The logistic model showed good discrimination ability (area under the curve = 0.844, discrimination slope = 0.359). Tenfold cross-validation showed 85.7% sensitivity, 60.7% specificity, 71.3% positive predictive value, and 76.1% negative predictive value for identification of PH, while the test group showed similar results (84.1%, 60.5%, 71.2%, and 76.7%, respectively). CONCLUSION: Cardiovascular data derived from CT pulmonary angiography are associated with PH, and a nomogram can be created that may facilitate identification of PH after exclusion of acute pulmonary embolism.

Acute Pancreatitis: Revised Atlanta Classification and the Role of Cross-Sectional Imaging.

OBJECTIVE: The 2012 revision of the Atlanta Classification emphasizes accurate characterization of collections that complicate acute pancreatitis: acute peripancreatic fluid collections, pseudocysts, acute necrotic collections, and walled-off necroses. As a result, the role of imaging in the management of acute pancreatitis has substantially increased. CONCLUSION: This article reviews the imaging findings associated with acute pancreatitis and its complications on cross-sectional imaging and discusses the role of imaging in light of this revision.

Intrahepatic cholangiocarcinomas mimicking other lesions.

BACKGROUND: While the typical features of large cholangiocarcinomas have been described extensively and are known to radiologists, atypical cholangiocarcinomas are not as well known and radiologists should be more aware of their features. Due to the increasing numbers of cross-sectional imaging studies performed for various reasons, cholangiocarcinomas may be more frequently detected incidentally when small, before they become symptomatic, and might be mistaken for other liver lesions. We studied the appearance of misdiagnosed cholangiocarcinomas. MATERIALS AND METHODS: This is a HIPAA-compliant, IRB-approved retrospective study. Our institutional database and teaching files were searched for cases of cholangiocarcinomas diagnosed between 2004 and 2014 that were initially misdiagnosed or considered indeterminate lesions on MRI or CT. Clinical data and radiological findings were collected. History of malignancy and risk factors for cholangiocarcinoma were recorded. The initial reported diagnosis and time to the correct diagnosis were noted, and the lesions were evaluated for size, enhancement, T1/T2 signal, diffusion restriction, ADC value, capsular retraction, biliary dilatation and the presence of satellite nodules. RESULTS: Nine examples of cholangiocarcinoma that met our inclusion criteria were identified: seven men and two women. All were small, with a mean size of 2.2 cm upon initial diagnosis. All showed a hypervascular pattern of enhancement without washout. Imaging features that are described in the literature as typical for cholangiocarcinomas, such as capsular retraction, satellite nodules, and peripheral biliary dilatation, were not seen. CONCLUSION: Cholangiocarcinomas can be misdiagnosed when they are small and hypervascular. This atypical hypervascular appearance is rare, and may mimic benign liver lesions and other malignant lesions, especially when small. Awareness of the confounding imaging features of these tumors should lead to a more meticulous evaluation of small hypervascular lesions, and may minimize the risk of misdiagnosing early-stage cholangiocarcinomas.

Beyond hepatic hemangiomas: the diverse appearances of gastrointestinal and genitourinary hemangiomas.

Hemangiomas are common lesions, best known for their appearance in the liver. Their appearance in less common locations, such as the gastrointestinal and genitourinary tracts, is less well known. We will review the typical and atypical appearance of hemangiomas in these locations on sonography, CT, and MRI.

Imaging of choledochal cysts.

Choledochal cysts are rare cystic dilatations of the intrahepatic and/or extrahepatic biliary tree, which may be mistaken for other cystic lesions if their characteristic features are not recognized. The etiology is unknown, and likely multifactorial, and it is uncertain whether they are congenital or acquired. Multiple imaging modalities can be used to diagnose choledochal cysts, including ultrasound, computed tomography, magnetic resonance (MR) cholangiopancreatography (MRCP), endoscopic retrograde cholangiopancreatography, and percutaneous transhepatic cholangiography. MRCP has replaced the more invasive techniques as the gold standard of diagnosis. In addition, MRCP is helpful in detecting an abnormal pancreaticobiliary junction, which is seen in the majority of choledochal cysts. Reaching a correct diagnosis is essential, given the associated risk of complications, including cholangitis, biliary strictures, stones, and malignancy, and accurately assessing the location and length of involvement is important for surgical planning. This review aims to familiarize radiologists with the different types of choledochal cysts and their imaging features according to the Todani classification.

Imaging of adrenal and renal hemorrhage.

Hemorrhage of the kidneys and adrenal glands has many etiologies. In the adrenal glands, trauma, anticoagulation, stress, sepsis, surgery, and neoplasms are common causes of hemorrhage. In the kidneys, reasons for hemorrhage include trauma, bleeding diathesis, vascular diseases, infection, infarction, hemorrhagic cyst rupture, the Antopol-Goldman lesion, and neoplasms. Angiomyolipoma and renal cell carcinoma are the neoplasms most commonly associated with hemorrhage in the kidneys and adrenal cortical carcinoma, metastases, and pheochromocytoma are associated with hemorrhage in the adrenal glands. Understanding the computed tomography and magnetic resonance imaging features, and causes of hemorrhage in the kidneys and adrenal glands is critical. It is also important to keep in mind that mimickers of hemorrhage exist, including lymphoma in both the kidneys and adrenal glands, and melanoma metastases in the adrenal glands. Appropriate imaging follow-up of renal and adrenal hemorrhage should occur to exclude an underlying malignancy as the cause. If there is suspicion for malignancy that cannot be definitively diagnosed on imaging, surgery or biopsy may be warranted. Angiography may be indicated when there is a suspected underlying vascular disease. Unnecessary intervention, such as nephrectomy, may be avoided in patients with benign causes or no underlying disease. Appropriate management is dependent on accurate diagnosis of the cause of renal or adrenal hemorrhage and it is incumbent upon the radiologist to determine the etiology.

Optimized definition of right ventricular dysfunction on computed tomography for risk stratification of pulmonary embolism.

OBJECTIVES: There is an ongoing discussion on the optimal right to left (RV/LV) diameter ratio threshold and the best definition of RV dysfunction on computed tomography pulmonary angiography (CTPA) for risk assessment of pulmonary embolism (PE). METHODS: On routine diagnostic CTPA, volumetric and diameter measurements (axial and reconstructed views) of the ventricles and reflux of contrast medium into the inferior vena cava (IVC) and hepatic veins were assessed in consecutive PE patients enrolled in a prospective single-center registry. In-hospital adverse outcome was defined as PE-related death, cardiopulmonary resuscitation, mechanical ventilation or catecholamine administration. RESULTS: Of 609 patients (median age, 69 [IQR, 56-77] years; 47 % male) included in the analysis, 68 patients (11.2 %) had an adverse outcome and 35 (5.7 %) died. While neither a RV/LV volume ratio ≥1.0 nor RV/LV diameter ratios ≥1.0 were able to predict an adverse outcome, higher thresholds increased specificity. Further, neither volumetric measurements nor reconstruction of images provided superior prognostic information compared to RV/LV ratios measured in axial planes. The combination of an axial RV/LV diameter ratio ≥1.5 with substantial reflux of contrast medium was present in 134 patients (22 %) and associated with the best prognostic performance to predict an adverse outcome in unselected (OR 3.7 [95 % CI, 2.0-6.6]) and normotensive (OR 2.8 [95 % CI, 1.1-6.7]) patients. CONCLUSION: A new definition of RV dysfunction (axial RV/LV diameter ratio ≥1.5 and substantial reflux of contrast medium to the IVC and hepatic veins) allows an optimized CTPA-based prediction of PE-related adverse outcome.

Radiologists' performance in the diagnosis of acute intestinal ischemia, using MDCT and specific CT findings, using a variety of CT protocols.

The aim of this study was to evaluate the performance of radiologists in the diagnosis of acute intestinal ischemia using specific multi-detector CT findings. The abdominal CT scans of 90 patients were retrospectively reviewed by three radiologists: an abdominal imaging specialist, an experienced general radiologist, and a senior resident. Forty-seven patients had surgically proven intestinal ischemia and comprised the case group, while 43 patients had no evidence of intestinal ischemia at surgery and comprised the control group. Images were reviewed in a random and blinded fashion. Radiologists' performance in diagnosing bowel ischemia from other bowel pathologies was evaluated. The sensitivity, specificity, and accuracy for diagnosing bowel ischemia were 89%, 67%, and 79% for the abdominal imager; 83%, 67%, and 76% for the general radiologist; and 66%, 83%, and 74% for the senior resident, respectively. The calculated kappa value for inter-observer agreement regarding the presence of bowel ischemia was 0.79. CT findings that significantly distinguished bowel ischemia from other bowel pathologies were decreased or absent bowel wall enhancement, filling defect in the superior mesenteric artery, small bowel pneumatosis, and gas in the portal veins or superior mesenteric vein. For most of these signs, there was good inter-observer agreement. Radiologists' performance in diagnosing bowel ischemia is good, but lower than previously reported since a significant amount of cases are evaluated using a suboptimal CT technique. Radiologists' experience and expertise have an important impact on their performance.

Spectral CT of the abdomen: Where are we now?

Spectral CT adds a new dimension to radiological evaluation, beyond assessment of anatomical abnormalities. Spectral data allows for detection of specific materials, improves image quality while at the same time reducing radiation doses and contrast media doses, and decreases the need for follow up evaluation of indeterminate lesions. We review the different acquisition techniques of spectral images, mainly dual-source, rapid kV switching and dual-layer detector, and discuss the main spectral results available. We also discuss the use of spectral imaging in abdominal pathologies, emphasizing the strengths and pitfalls of the technique and its main applications in general and in specific organs.

Detection of severe pulmonary hypertension based on computed tomography pulmonary angiography.

Pulmonary hypertension (PH) is often diagnosed late in the disease course. As many patients may undergo computed tomography pulmonary angiography (CTPA) for exclusion of pulmonary embolism (PE), we aimed to create a model that can detect the existence of PH and grade its severity. Consecutive patients who underwent CTPA which was negative for PE, and echocardiography study within 24 h, were included. The CT parameters evaluated to assess PH were: the diameters of the main pulmonary artery (MPA), ascending aorta (AA), calculation of each heart chamber volume, and the severity of reflux of contrast material. Randomly, 70% of patients were included in the model creation group, and 30% were used to validate the model. The final study group included 740 patients, 268 male patients, median age 72 years. 374 patients (51%) had PH, of them 94 (13%) had severe PH on the echocardiography. Right atrium (RA) and Left atrium (LA) volume indices were the strongest parameter to indicate PH (area under the curve, AUC = 0.738 and 0.736, respectively), while Right ventricle (RV) and RA volume indices were the strongest parameter to identify severe PH (AUC = 0.735 and 0.715, respectively) with MPA diameter being the least influential indicator (AUC = 0.623). Using the patients age, gender, and multiple CTPA parameters, we created a model for predicting the existence of severe PH. After validation, the model demonstrated 91% sensitivity and a negative predictive value of 97%. Applying our models, CTPA can be used to identify severe PH immediately after the completion of CTPA exam.

Imaging of the Liver Following Interventional Therapy for Hepatic Neoplasms.

Locoregional therapies for hepatic neoplasms have distinctive imaging features after treatment, different from those observed after systemic therapy. As these therapies are becoming more common, it is important that radiologists be aware of the imaging appearance of tumors after locoregional therapies to correctly diagnose treatment response or failure and potential complications. This article reviews the imaging recommendations and findings after intra-arterial therapies (chemoembolization and radioembolization) and ablative therapies.

Magnetic resonance imaging of pancreatic metastases from renal cell carcinoma.

Pancreatic metastases are rare but are thought to be most commonly from renal cell carcinoma (RCC). These metastases can present many years after the initial tumor is resected, and accordingly, these patients require prolonged imaging follow-up. Although the computed tomographic findings of these metastases have been extensively reviewed in the literature, little has been written about the magnetic resonance imaging appearance of these metastases. Pancreatic metastases from RCC are typically T1 hypointense and T2 hyperintense. After intravenous administration of gadolinium, they are typically hypervascular and less commonly hypovascular. Chemical shift and diffusion-weighted imaging can aid in the diagnosis of these metastases.

Revascularization of the left anterior descending artery with drug-eluting stents: comparison with arterial off-pump surgery.

BACKGROUND: This study compared early results of left anterior descending artery (LAD) stenting using drug-eluting stents (Cypher) with off-pump bilateral internal thoracic arterial (BITA) grafting. METHODS: From June 2002 to June 2003, 200 consecutive patients underwent myocardial revascularization of the LAD territory, 100 by Cypher and 100 by BITA. The 2 groups were similar; however, left main disease and triple-vessel disease (20% and 75% versus 2% and 28%), age >70 (36% versus 17%) and intraaortic balloon pump (7% versus 0%) were more prevalent in the BITA group, and prior percutaneous coronary angiogplasty to the LAD was more prevalent in the Cypher group (28% versus 16%). RESULTS: The number of coronary vessels treated per patient in the BITA group was higher (2.7 versus 1.45, P < .01). Thirty-day mortality was 1% in the BITA group and 0% in the Cypher group. Mean follow-up was 12 months. There was 1 late death in each group. Angina returned in 32% of the Cypher group and in 1% of the BITA group. There were 9 reinterventions in the Cypher group: 7 coronary angioplasties (including 2 to the LAD) and 2 surgical interventions. There was neither recurrent angina nor reintervention in the surgical group. CONCLUSIONS: Despite a higher risk profile of patients treated with BITA, their clinical outcome is better. A longer and more complete angiographic follow-up is required to determine the role of drug-eluting stents in LAD revascularization.

Revascularization of left anterior descending artery with drug-eluting stents: comparison with off-pump surgery.

BACKGROUND: This study compares early results of left anterior descending coronary artery stenting using drug-eluting stents (Cypher) with off-pump coronary artery bypass grafting (OPCAB). METHODS: From June 2002 to June 2003, 386 consecutive patients underwent myocardial revascularization of the left anterior descending coronary artery territory, 130 by Cypher and 256 by OPCAB. After matching for age, sex, and extent of coronary artery disease, two groups (each with 94 patients) were used to compare the two revascularization modalities. The two groups were similar; however, old myocardial infarction and intraaortic balloon pump were more prevalent in the OPCAB group, and prior percutaneous transluminal coronary angioplasty was more prevalent in the Cypher group. RESULTS: The number of coronary vessels treated per patient in the two groups was similar (1.54 versus 1.34, OPCAB and Cypher, respectively; not significant). Mean follow-up was 18 months. Thirty-day mortality was 1% in the OPCAB group and 0% in the Cypher group. There was one late death in each group. Angina returned in 31% of the Cypher group and in 11% of the OPCAB group (p = 0.001). There were nine reinterventions in the Cypher group: seven coronary angioplasties (including two to the left anterior descending coronary artery) and two surgical interventions. There were two reinterventions (percutaneous transluminal coronary angioplasty) in the surgical group (p = 0.042). CONCLUSIONS: Despite the higher risk profile of patients treated with OPCAB, their clinical outcome is better. A longer and more complete angiographic follow-up is required to determine the role of drug-eluting stents in left anterior descending coronary artery revascularization.