Diagnosis

Biliary Ascariasis

Findings

Select images from cholangiogram reveal a smooth, linear filling defect within the common hepatic and extending into the left hepatic ducts. There is no significant biliary dilatation to indicate obstruction at this time.

Discussion

Infection by the parasite Ascaris lumbricoides is thought to affect almost a quarter of the world's population. The southeastern region is the portion of United States most affected. Adult Ascaris worms may grow to a few inches in length, and tend to live within the jejunum. Following infection, the worms may stay within the small bowel, subsequently resulting in obstruction. Another possibility includes migration into the biliary system, including the gallbladder and pancreatic duct. This can result in biliary obstruction, cholecystitis or pancreatitis. Ultrasound can be utilized to diagnose Ascaris infection of the biliary true with good reliability. More importantly, it is obviously accurate in diagnosing the resultant biliary dilatation. The worms appear as thin, elongated echogenic structures, or else may demonstrate a bull's eye appearance when viewed in cross section. One of the more interesting appearances is that of a central lucency within the echogenic worm, thought to represent the digestive system. As in this case, the Ascaris worms may also be identified within the biliary system by cholangiography. They are identifiable as smooth bordered, elongated filling defects. Removal of the worms themselves may also be attempted during the ERCP procedure.

Friedman and Dachman, Radiology of the Liver, Biliary Tract and Pancreas. Mosby, Baltimore, 1994