Ultrasonographic appearance of Ascaris lumbricoides in the small bowel.

Roundworm infestation, one of the most common helminthic diseases worldwide, is caused by Ascaris lumbricoides, one of the largest parasites that infests the human bowel. A lumbricoides is virtually universal at some stage of childhood in semitropical and tropical regions. This study describes our experience with the ultrasonographic appearance of intestinal ascariasis in 84 patients, 2.5 to 42 years of age, examined over 2 years beginning October 1997. The patients' conditions ranged from acute intestinal obstruction to no clinical features pertaining to obstruction. Ultrasonographic examination was performed with an Echocee power Doppler real-time unit with a variable-frequency 3.7-MHz convex, 7.5-MHz linear probe. In longitudinal section the Ascaris worm presented as a linear intraluminal mass with 3 or 4 linear echogenic interfaces; in the cross section, it was round, sometimes appearing as a "target" sign. Some worms also showed serpentine movements. Sonographic examination of the patients in the left lateral decubitus position after ingestion of water improved detection and visualization of the worms in some cases. It is concluded that A lumbricoides in the small bowel has a sonographic appearance that can be recognized by the wary observer.