Rectal anisakiasis removed during colonoscopy for ascending colon intussusception: A case report

An 84-year-old man presented with abdominal pain and diarrhea. Contrast-enhanced computed tomography revealed a target sign in the ascending colon, leading to the diagnosis of intussusception. An emergent colonoscopy was performed to evaluate the etiology and attempt reduction. Although mild mucosal edema was observed in the ascending colon, no persistent intussusception or tumorous lesions were identified. An Anisakis larva penetrating the mucosa of the lower rectum was detected and removed using biopsy forceps. The patient resumed oral intake and was discharged home. Although no Anisakis larva was identified in the ascending colon, transient intussusception triggered by anisakiasis was suspected. While intussusception in adults is most commonly associated with tumorous lesions, anisakiasis should be included in the differential diagnosis. Prompt endoscopic evaluation, careful dietary history taking, and close collaboration with surgeons assist in accurate diagnosis and appropriate management.