Unenhanced CT scan showing Central dot sign is characteristically seen in:

Central dot sign is a characteristic feature of Carolis disease. On enhanced CT and MRI, central dot sign is indicated by the presence of tiny dots with strong enhancement within dilated intrahepatic ducts reflecting intraluminal poal vein radicles. Ultrasound is the best initial imaging study it shows irregular dilatation of the large intrahepatic ducts. Cholangiography shows diveiculum like sacculi of intrahepatic bile ducts of varying size, shape and distribution. Hepatic scintigraphy with Tc 99m diethyl IDA shows typical beaded appearance of dilated intrahepatic bile ducts.