MRCP of a 28-year-old woman with recurrent cholangitis shows multiple saccular dilatations of the intrahepatic bile ducts. On contrast-enhanced CT, tiny strongly enhancing dots are seen centrally within these dilated ducts. This 'central dot sign' represents:

• A Intraluminal calculi within the cystic ducts
• B Mucosal hyperplasia within congenital biliary cysts
• C Portal vein branches surrounded by dilated bile ducts ✓
• D Hepatic artery branches feeding inflamed duct walls

Explanation

The central dot sign is characteristic of Caroli disease, a type V choledochal cyst defined by segmental saccular dilatation of intrahepatic bile ducts. The enhancing central dots are portal radicles that appear to project into the lumen because the surrounding bile ducts are massively dilated around them. Calculi may coexist in Caroli disease but do not enhance, and mucosal proliferation is a feature of adenomyomatosis of the gallbladder, not of intrahepatic ducts.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.