Oct. 17 (HealthDay News) -- Eating raw or undercooked seafood -- such as sushi and sashimi -- increases the risk of infection by parasitic worm larvae. And such infection can cause severe stomach and intestinal problems such as diarrhea, cramping, and vomiting that warrant a visit to a hospital emergency department, say two cases studies by Japanese researchers.

Raw or undercooked seafood can contain larvae of a parasitic worm called Anisakis. While the worm itself can't survive in humans, the larvae can attach to the tissues lining the stomach and intestines, resulting in severe abdominal symptoms, the researchers said.

In most cases, the larvae eventually die, and the symptoms usually resolve on their own. However, some patients may experience small bowel obstruction.

Anisakiasis in the stomach can easily be diagnosed by endoscopy, but anisakiasis of the small intestine is more difficult to diagnose, the study authors said.

In these case studies, abdominal X-rays showed air-fluid levels suggesting a small intestinal obstruction in both patients. Doctors used multidetector-row computed tomography (MDCT) to obtain high-quality images of the small bowel and found that both patients had an intestinal blockage caused by the presence of Anisakis larvae. Fluid replacement and rest relieved their symptoms.

Anisakiasis symptoms can be similar to those of other gastrointestinal problems and may be misdiagnosed as appendicitis, stomach ulcers, or peritonitis, the researchers noted. They said anisakiasis should be considered in the differential diagnosis of small intestinal obstruction.

The studies were expected to be presented Oct. 15 at the American College of Gastroenterology annual meeting, in Philadelphia.

SOURCE: American College of Gastroenterology, news release, Oct. 15, 2007