Primary sclerosing cholangitis (PSC) is a chronic progressive inflammatory disease of the bile ducts that leads to multifocal bile duct fibrosis, strictures, cholestasis, liver parenchymal changes, and ultimately cirrhosis. It more commonly occurs in young adults, with a variety of clinical and imaging manifestations. The cause of the disease is not known, but it has a strong association with inflammatory bowel disease and can overlap with other autoimmune diseases, including autoimmune hepatitis and immunoglobulin G4-related disease. Patients are predisposed to various hepatic and extrahepatic deteriorating complications, such as bile duct and gallbladder calculi, acute bacterial cholangitis, liver abscess, and portal hypertension, as well as malignancies including cholangiocarcinoma (CCA), gallbladder cancer, and colorectal carcinoma. Imaging has an essential role in diagnosis, surveillance, and detection of complications. MR cholangiopancreatography and endoscopic retrograde cholangiopancreatography have high specificity and sensitivity for detection of primary disease and assessment of disease progression. However, many patients with PSC are still diagnosed incidentally at US or CT. Novel imaging techniques such as transient elastography and MR elastography are used to survey the grade of liver fibrosis. Annual cancer surveillance is necessary in all PSC patients to screen for CCA and gallbladder cancer. Familiarity with PSC pathogenesis and imaging features across various classic imaging modalities and novel imaging techniques can aid in correct imaging diagnosis and guide appropriate management. The imaging features of the biliary system and liver parenchyma in PSC across various imaging modalities are reviewed. Imaging characteristics of the differential diagnosis of PSC, clinical associations, and complications are described. Finally, the role of imaging in evaluation of PSC progression, pre-liver transplant assessment, and post-liver transplant disease recurrence are discussed. © RSNA, 2019 • radiographics.rsna.org

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Background and purpose Performing a proper causative workup for ischemic stroke patients is essential as it guides the direction of primary and secondary preventions. We aim to investigate the etiological evaluation of these patients in university and nonuniversity hospitals. Method We enrolled subjects from the Persian Registry of Cardiovascular Disease–stroke. Stroke patients were categorized base on an etiological-based classification (Trial of Org 10172 in Acute Stroke Treatment or TOAST) into five groups. We also separated patients with ischemic stroke of undetermined etiology due to incomplete standard evaluation from ischemic stroke of undetermined etiology due to negative standard evaluation. The etiological subtypes and diagnostic evaluations were compared between the two hospital groups. Result Ischemic stroke of undetermined etiology was the most common subtype overall (43%). The prevalence of ischemic stroke of undetermined etiology (incomplete standard evaluation) was significantly higher in patients evaluated in nonuniversity hospitals versus university hospital (46.2% vs. 22.3%). Patients with ischemic stroke of undetermined etiology (negative standard evaluation) and large-artery atherosclerosis were significantly more prevalent in university hospitals (10.3% vs. 4.6% and 13.9% vs. 4.4%, respectively). All diagnostic workups were performed more significantly for university hospital patients. Patients with Ischemic stroke of undetermined etiology (negative standard evaluation). Patients were significantly younger (64.91 ± 14.44 vs. 71.42 ± 12.93) and had lower prevalence of risk factors such as hypertension (48.5% vs. 65.4%) and diabetes (19.4% vs. 33.1%) than patients in ischemic stroke of undetermined etiology (incomplete standard evaluation) subgroup. University hospital patients had better clinical outcomes in terms of mortality and degree of disability during one-year follow-up. Conclusion The high clinical burden of ischemic stroke of undetermined etiology especially in nonuniversity hospitals shows the rational for promoting ischemic stroke evaluation and providing specialized stroke centers for these hospitals in a developing country like Iran.