A case of solitary rectal diverticulum presenting with a retrorectal mass

Abstract

Colonic diverticula are common whereas but rectal diverticula are very rare, with only sporadic reports in the literature since 1911. Most patients with rectal diverticula are diagnosed incidentally, inflammatory processes may have developed at the time of the diagnosis. We report the case of a 42-year-old woman presenting with a retrorectal mass that was detected incidentally. She was suspected of having a rectal diverticulum by transrectal ultrasonography and magnetic resonance imaging. However, the colonoscopic findings were unremarkable. A rectal diverticulum was confirmed intraoperatively, and a transanal diverticulectomy was performed.

Keywords: Magnetic resonance imaging; Rectal diverticum; Retrorectal mass; Transrectal ultrasonography.

Fig. 1

Transrectal ultrasonography (TRUS) and magnetic resonance imaging (MRI). (A) An out-pouching of the rectal lumen was revealed on TRUS (arrowhead). (B) MRI revealed a posterior cystic lesion with a small opening tract (arrow) to the rectal lumen in the lower rectum (T1-weighted).

Fig. 2

Colonoscopy. (A) Forward colonoscopy did not reveal a luminal defect or mucosal elevation in the rectum. A previous hemorrhoidectomy scar was identified at the level of the puborectalis ring. (B) Colonoscopic retroflexion also revealed no remarkable findings.

Fig. 3

Surgical specimen and histologic findings. (A) A 2-cm diverticulectomy specimen is shown (arrowhead, mucosa; arrow, rectal muscle). (B) Histologic examination revealing the entire rectal layer with the mucosa, submucosa, and proper muscle (H&E stain, ×40).