35-year-old south east Asian female patient came with complaints of right iliac fossa pain for the past 2 days.
On ultrasound imaging of the abdomen the intestinal lumen contains tube-like echogenic structures which on cross sections appear as round echogenic wall (Fig. 1, 2, 3). Eccentrically placed linear hyperechoic structure and central hypoechoic structure noted. These structures representing the roundworms are noted in the ileal lumen.
Ascaris lumbricoides is a roundworm and can grow to a length of 49 cm. Ascaris lumbricoides infection or ascariasis can present with abdominal or respiratory symptoms. Infection occurs when the ingested fertilised egg develops into a larva which penetrates intestinal wall and reaches the vessels. The migrating larva during this stage can cause peritonitis. Then it enters the pulmonary circulation after passing through the liver and heart via the blood stream. Within the lung it could manifest as Loefflers syndrome.
In 3 weeks duration, the larva matures and re-enters the small intestine through coughing and swallowing and finally matures to an adult worm. When multiple adult worms are within the intestinal lumen they can cause intestinal obstruction. The adult worm can travel retrograde within the small bowel and can pass through the ampulla of Vater to enter into the biliary tree and to cause acute biliary obstruction.
The worms measures 2 to 6 mm in diameter and 15 to 49 cm in length. The female worms are longer and wider in comparison with the male and can lay 200, 000 eggs per day. 
When visualized in ultrasound, the worm appears tube-like with parallel echogenic lines within the intestinal lumen or within the bile ducts and on cross sectional view appears round with echogenic wall. When noted within the bile duct it can give a target appearance and appears similar to the biliary stent .
Ascariasis is treated with antihelminthic drugs. Ascaris lumbricoides reinfection occurs rapidly even after treatment . Being a soil-transmitted helminth parasite, to reduce the ascariasis infection in highly endemic countries prioritization of improved sanitation together with preventive chemotherapy and health education would be required to interrupt transmission .
Differential Diagnosis List