Purpose: To illustrate the CT findings of gastrointestinal anisakiasis.
Subjects and methods: The Institutional Review Board approving this retrospective study waived the requirement for informed consent. Review of our emergency department's clinical records from September 2008 to January 2012 identified 41 consecutive patients who were diagnosed with gastrointestinal anisakiasis. 20 patients were diagnosed with gastric anisakiasis with endoscopically proven Anisakis larvae, and 21 patients were diagnosed with intestinal anisakiasis with positive test results for anti-anisakidae antibody and the presence of intestinal lesions on CT. Two radiologists retrospectively assessed the CT findings.
Results: The mean time delay from raw fish ingestion to symptom onset was 5.2 h (range 0.5-24 h) in gastric anisakiasis and 39 h (range 12-120 h) in intestinal anisakiasis. Gastric anisakiasis showed marked submucosal edema of the gastric wall (20/20 patients, 100%), increased attenuation of adjacent fat (19/20, 95%), and ascites (14/20, 70%) on CT. Intestinal anisakiasis showed marked submucosal edema of the intestine (21/21 patients, 100%) without showing complete intraluminal occlusion, ascites (21/21, 100%), increased attenuation of adjacent fat (19/21, 90%), and fluid collection in the distal segment of the constricted small intestine (13/21, 62%) on CT.
Conclusion: Severe submucosal edema with ascites is a characteristic finding of gastrointestinal anisakiasis when compared with other forms of gastroenteritis. When CT shows the typical findings of gastrointestinal anisakiasis, radiologists may suggest the possibility of clinically undiagnosed anisakiasis, especially in intestinal anisakiasis as the diagnosis is sometimes difficult due to the long interval between food intake and symptom onset.