eP483 - An Unusual Case of Rectal Diverticulum with Symptomatic Prolapse

Purpose/Background: Rectal diverticula are rare, with an estimated incidence of < 0.1%. They are usually solitary, true diverticula with large size and effected by intraabdominal pressure. Various etiological factors may contribute to development, including congenital defects, constipation, heterotopic gastric mucosa, rectal trauma, or perirectal abscess. Protective factors include splaying of the tineae coli, rectal pressure gradient, and oblique angle of the vasa recta entering the rectum vs. perpendicular entry of the sigmoid colon.Methods/Interventions: We report a 50-year-old male with a remote history of hemorrhoidectomy who presented with one-year of prolapsing rectal tissue and intermittent bleeding. His physical and anoscopic exam were unremarkable. When examined straining on the toilet, he was found to have a prolapsing rectal mass. He underwent a complete colonoscopy that showed a large rectal diverticulum just above the dentate line with impacted stool (Figure 1). A pelvic MRI revealed the presence of a posterior rectal diverticulum measuring 5.0 x 4.7 x 3.3 cm (Figure 2). Excision was recommended, and he underwent exam under general anesthesia that showed a true diverticulum of the distal posterior rectum just proximal to the dentate line. A transanal diverticulectomy with full-thickness partial proctectomy was performed and hand-sewn closure of rectal defect. Pathology showed true rectal diverticulum without dysplasia. He has since been seen in follow-up with no symptoms or residual defect on rectal exam.Results/Outcomes: The presentation and diagnosis of symptomatic rectal diverticulum is exceedingly rare. Most cases are incidentally discovered, often in conjunction with sigmoid diverticulosis. This patient exhibited tissue prolapse with unremarkable anoscopy that prompted further evaluation. It is unclear if remote hemorrhoidectomy played any role, but rather a congenital anatomic predisposition and constipation as underlying etiology. MRI of the pelvis is the preferred imaging modality for characterizing these lesions. They are often benign, with an uncertain malignant potential due to rarity and limited to case reports. For benign lesions without symptoms, some authors advocate for observation. However, symptomatic cases are typically managed with surgical resection, although endoscopic diverticulectomy and rectopexy have also been reported. The choice of approach may be influenced by the location of the diverticulum. In our case, given location in the distal rectum at the level of the dentate line, a transanal approach allowed for complete excision.Conclusion/

Discussion: Rectal diverticulum are often discovered incidentally but may present with symptoms of tissue prolapse, bleeding, or obstruction. These lesions can be best characterized by endoscopy and pelvic MRI. The malignant potential of these lesions is unclear, and asymptomatic cases can consider observation. For symptomatic lesions, intervention with endoscopic or surgical management is warranted."Figure 1

Colonoscopy Findings. Flexible colonoscopy in retroflexion view of giant rectal diverticulum.
Figure 2

MRI Pelvis. Representative image of rectal-cancer protocol MRI. Ovoid structure posterior to the anorectal junction with internal signal consistent with stool arising from the posterior anorectal juction measuring 5.0 x 4.7 x 3.3 cm."