Imaging of ascariasis.

Ascaris lumbricoides is one of the most common parasitic infestations of the gastrointestinal tract worldwide. During the intestinal phase of the disease, the adult worms usually remain clinically silent, sometimes causing a variety of non-specific abdominal symptoms. When present in large numbers, the worms may get intertwined into a bolus, causing intestinal obstruction, volvulus or even perforation. Occasionally, the adult Ascaris worm may migrate into the Vater's ampulla and enter the bile duct, gall bladder or pancreatic duct, leading to a variety of complications such as biliary colic, gallstone formation, cholecystitis, pyogenic cholangitis, liver abscess and pancreatitis. Imaging plays a significant role in showing the presence of worms and possible complications in intestinal as well as hepatobiliary ascariasis. This pictorial essay aims to illustrate various imaging features of ascariasis and its associated complications.