Associate Professor of Radiology Tehran University of Medical Sciences, Imam Khomeini Hospital Complex, Tehran, Iran
Biliary strictures are challenging issues. The majority of them are malignant unless otherwise confirmed. But up to 30% of biliary strictures are benign. Many of these strictures remain indeterminate after laboratory and imaging workup, and even tissue sampling. About 15-24% of patients who underwent surgery for suspected malignant biliary strictures, were finally found to have benign etiology. Detailed history focusing on alarm signs and, a physical exam is mandatory in approaching biliary strictures. Obstructive jaundice and elevated bilirubin increase the likelihood of being malignant. PSC, Ig G4- related cholangitis, iatrogenic strictures, Mirrizi syndrome, and chronic pancreatitis are some of the benign causes of biliary strictures. Psc is characterized by multiple short-segment strictures in intrahepatic and extrahepatic bile ducts. PSC harbors an increased risk of cholangiocarcinoma, these patients should be followed with serial MRI-MRCP and CA- 19-9 checking. Detecting superimposed cholangiocarcinoma in PSC poses a difficult challenge in such patients. Developing a mass is a direct sign in favor of cholangiocarcinoma. Indirect signs include progressive ductal dilation, marked ductal dilation, severe ductal narrowing and luminal obliteration, and significant ductal wall thickening. IgG4-related cholangitis may mimic cholangiocarcinoma but represent a long-segment stricture with significant circumferential smooth bile duct wall thickening that shows delayed enhancement but the bile duct lumen is preserved despite severe stricture. The pancreatic portion is most commonly involved followed by the hilar region. extra biliary involvement of the pancreas, kidneys, or retroperitoneum is an ancillary finding. Imaging findings cannot differentiate benign from malignant strictures in many cases, but the presence of a mass, more prominent bile duct wall thickening of more than 2-3mm, asymmetric wall thickening, indistinct outer margin, and luminal irregularity, bile duct luminal obliteration, relative long segment strictures more than 21mm, and portal or delayed hyperenhancement relative to the liver parenchyma are described in the literature in favor of malignant strictures.