Itʼs Not Always the Diverticula: A Rare Case of Obscure Overt Lower Gastrointestinal Bleed Resulting From a Fistulous Tract Between Rectum and Seminal Vesicle Secondary to Metastatic Prostate Adenocarcinoma

Abstract

Diverticula and hemorrhoids are the most common etiology of lower gastrointestinal bleed (LGIB) with other causes including angioectasias, malignancy, colitis (ischemic, infectious, and inflammatory), post procedural, and disorders of the anorectal region. In rare instances of surgical prostatic manipulation, LGIB has occurred. We present a rare case of fistulous tract formation resulting in ongoing obscure, overt LGIB secondary to metastatic adenocarcinoma of the prostate. We present a case of a 74 year old male with a past medical history of hypertension, paroxysmal atrial fibrillation not on anticoagulation, hemorrhoids, benign prostatic hypertrophy, and diverticulosis, who presented to his urologist with complaints of urinary retention Computed tomography (CT) of the abdomen and pelvis revealed enlarged prostate and seminal vesicle mass thought likely to be a cyst which led to a transrectal biopsy. Approximately 1 month later, patient developed acute lower gastrointestinal bleeding and underwent colonoscopy that revealed pan mild diverticulosis and hemorrhoids. The patient continued to have intermittent lower gastrointestinal bleeding requiring multiple hospitalizations and blood transfusions. Multitude of testing including EGD, multiple colonoscopies, tagged red blood cell scans and computed tomography angiography failed to localize the bleeding and patient underwent sigmoidectomy. He continued to bleed flexible sigmoidoscopy noted a brief jet of bright red blood coming from the anus near the dentate line that stopped spontaneously.. Patient underwent surgical exploration with colorectal and urology and tumor, confirmed as adenocarcinoma of the prostate, was found to be replacing the space between the rectum and the seminal vesicle likely stemming from the seminal vesicles and a noted defect in the left anterior rectum which was identified as the site of the fistula approximately 2 centimeters in size. The defect was closed during surgery. Following these procedures there was resolution of the hematochezia Although rare, metastatic adenocarcinoma of the prostate can lead to the development of a rectal-seminal vesicle fistula causing LGIB. Brief review of the literature did not return any reported cases of rectal-seminal vesicle fistula caused by tumor involvement. A thorough evaluation of the entire patient including all comorbities should be completed when evaluating etiology of recurrent lower gastrointestinal bleeding.