"Scoping-around" a sigmoidorectal intussusception: a pitfall of flexible sigmoidoscopy

A 66-year-old woman presented with 3-month history of progressive constipation and occasional bright red per-rectal bleeding. An urgent flexible sigmoidoscopy (FS) showed an abnormal lesion within the anal canal and biopsy showed tubulovillous adenoma with low-grade dysplasia. She mentioned "no" response to a preparatory enema given before FS. The patient presented 4 days after FS with absolute constipation and passing a "jelly-like" substance since the procedure. A large soft tissue lump with "currant jelly" mucus discharge was noted on per-rectal examination. An abdominal x ray was suggestive of distal large bowel obstruction and a water-soluble contrast enema suggested sigmoidorectal intussusception. The intussusception was irreducible with rigid sigmoidocopy and therefore the patient underwent sigmoid resection and Hartmann's procedure, which showed a distal sigmoid polyp as a lead point for the intussusception. Retrospectively looking into the case, the intussusception was present during FS, but was scoped-around and therefore lesion was considered to be in the anal canal.