Radiological Diagnosis

The characteristic features of intestinal anisakiasis on small bowel barium study include marked edematous changes involving the bowel wall with thickening and blunting of the valvulae conniventes, at times presenting a "picket fence" appearance (Figs. 11.7 and 11.8). There is irregular narrowing of the bowel lumen with segments of stenosis, which may be 20 to rarely 80 cm long, usually present in the ileum but occasionally in the jejunum and the right colon. As a result of the luminal narrowing, there is dilatation of the more proximal small bowel, which can be manifest on plain films as an ileus of varying severity, often with air-fluid levels (Fig. 11.7C). Thus, the radiographic findings are compatible with the pathological features of anisakiasis, namely, a phlegmonous reaction of the intestine manifest by edematous thickening of the bowel wall with marked eosinophilic and other cellular infiltrate involving the submucosa and, at times, other layers. The overall radiological appearance will suggest regional enteritis (Crohn's disease) or perhaps tuberculosis or submucosal hemorrhage, and will thus erroneously agree with the probable clinical and subsequent surgical impression.

In two of the 12 patients with intestinal anisakiasis reported by Matsui et al, a thread-like filling defect suggesting an Anisakis worm was visualized on the small bowel barium study (Fig. 11.7F). Infestation in the colon and rectum is unusual , but in a report by Matsumoto et al (1992), air contrast barium enemas performed 2 to 4 days after acute onset of symptoms were beneficial since Anisakis worms could be demonstrated radiologically in 4 of 6 patients, whereas colonoscopy performed 1 to 7 days after onset of symptoms failed to detect any worms. The right colon was involved with edema, causing luminal narrowing and thumbprinting on barium enema and colonoscopy.

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Fig. 11.7 Intestinal anisakiasis in four different Japanese patients, all of whom developed epigastric or lower abdominal pain within 24 hours after eating raw or pickled mackerel. (A) Severe edema has caused narrowing of the hepatic flexure of the colon as shown by air-contrast barium enema in a 62 year-old woman. (B) Follow-through small bowel study shows coarse thickening and edema of the mucosal folds in the ileum and dilatation of the more proximal bowel in a 26 year-old man. (C) Plain abdominal radiograph reveals multiple fluid levels in the small bowel in a 59 year-old man. Intestinal anisakiasis in different Japanese patients, all of whom developed epigastric or lower abdominal pain within 24 hours after eating raw or pickled mackerel. (D) His small bowel barium study shows multiple dilated jejunal loops filled with fluid and undigested food, felt to be secondary to partial bowel obstruction from anisakiasis, which was diagnosed immunologically. His symptoms stopped on the fourth hospital day. (E) Double-contrast barium study of the ileum reveals edematous valvulae conniventes without ulceration in a 39 year-old man. (F) Close-up view of (E) shows a thread-like filling defect in the edematous segment of ileum, felt to represent an Anisakis worm. (Reprinted from Matsui et al: Intestinal anisakiasis. Radiology 157:299-302, 1985.

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Fig. 11.8 Intestinal anisakiasis in two different Japanese patients who developed abdominal discomfort after eating infected raw fish. (A) Compression radiograph from a small bowel series shows irregular "picket fence" mucosal thickening of the bowel. (B) Small bowel barium study shows a long edematous loop with widened Kerckring folds. The usual length of involved bowel in intestinal anisakiasis is 20 cm or less, but edematous, narrowed segments as long as 80 cm can be seen at times. (Courtesy of Dr. T. Matsui and Radiology, 1985).