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Vol. 4. Núm. 3.
(Julio - Septiembre 2021)
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Vol. 4. Núm. 3.
(Julio - Septiembre 2021)
Images in medicine
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Asymptomatic anisakiasis invading ascending colon after eating mackerel-sushi
Anisakiasis asintomática que invade el colon ascendente después de comer caballa-sushi
Koichi Soga
Omihachiman Community Medical Center, Department of Gastroenterology, 1379 Tsuchida-cho, Omihachiman, Shiga 523-0082, Japan
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Clinical presentation

A 69-year-old, Japanese man underwent a scheduled screening colonoscopy, following a positive stool occult blood test. Colonoscopy revealed a mobile foreign object, which appeared whitish in white light (Fig. 1A). The object was showed extremely strong adherence to the mucosa of the ascending colon. The 20-mm long nematode was extracted using forceps (Fig. 1B) and identified as Anisakis spp. (Fig. 1C). Although the patient had consumed mackerel-sushi 3 days ago, there were no symptoms. Upper endoscopy screening performed on the same day did not show any anisakiasis-related changes or Anisakis itself.

Fig. 1.

Colonoscopy revealed a mobile whitish object among the folds, with extremely strong adherence to the mucosa of the ascending colon (A). The nematode was extracted using forceps (B) and identified as a 20-mm long Anisakis spp. (C).


Anisakis is globally prevalent and frequently infects consumers of raw or barely cooked fish. Although gastric anisakiasis is common in Japan, colonic anisakiasis is rarely reported. Furthermore, asymptomatic colonic anisakiasis is very rare. To our knowledge, there exist only 6 cases (including our case) in the English literature globally. Anisakis was found in the ascending colon in 3 cases and in the descending colon, sigmoid, and rectum in 1 case each. Three cases were caused by mackerel and one each by bonito, anchovy, and an unknown source. As no anthelmintic agents are available for this nematode, endoscopic removal of the Anisakis is required in acute cases.

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Not commissioned; externally peer reviewed.


The authors have not received any grant for this research from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interests

None declared.

Copyright © 2021. The Author
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