Which nematode causes ileocecal infection and may obstruct the biliary tree?

• A. Ancylostoma duodenale
• B. Trichinella spiralis
• C. Ascaris lumbricoides
• D. Enterobius vermicularis

Answer: (C)

Ascaris lumbricoides is the nematode that fits this scenario because it is known for its potential to migrate from the intestinal lumen into the biliary and pancreatic ducts. After establishing in the small intestine, these worms can wander through the ampulla of Vater and obstruct the biliary tree, leading to biliary colic, cholangitis, or even pancreatitis. In heavy infections, the worm burden in the ileocecal region can also cause intestinal symptoms or obstruction.

Other nematodes listed have different clinical patterns. Hookworms like Ancylostoma duodenale mainly cause iron-deficiency anemia from blood loss in the small intestine and do not characteristically obstruct the biliary tract. Trichinella spiralis causes trichinellosis from eating undercooked meat, with larvae encysting in muscle tissue and presenting with GI symptoms followed by myositis, not biliary obstruction. Enterobius vermicularis (pinworm) typically causes perianal itching and is confined largely to the large intestine, without biliary tree involvement.