Introduction: Heterotopic gastric mucosa (HGM) is the most reported epithelial heterotopia and refers to morphologically normal tissue displaced in a foreign anatomical site distinctly demarcated from the surrounding mucosa and entirely separated from its organ of origin. HGM is typically identified endoscopically as a polyp, diverticula or ulcer and can be seen anywhere in the gastrointestinal tract. HGM is usually a benign condition. It may present asymptomatically or with painless rectal bleeding.
Case Description/Methods: 45-year-old gentleman with a medical history of hypertension, presented to the outpatient clinic for a screening colonoscopy. He reported symptoms of rectal pressure and occasional loose bowel movements. The patient underwent routine colonoscopy which was significant for multiple adenomatous polyps, none of which had evidence of high-grade dysplasia. A 12mm umbilicated subepithelial rectal mass was found in the rectum, and biopsies revealed heterotopic gastric mucosa. Subsequently, a pelvic MRI was done which reported a 1.2 x 1.9cm polypoid lesion in the left lower rectum, approximately 7cm above the anal verge, without invasion through the rectal wall and with intact muscularis propria. Endoscopic ultrasound (EUS) showed a subepithelial lesion in the rectum that measured up to 7mm in thickness and 19mm in diameter. An intact interface was seen between the lesion and the muscularis propria suggesting a lack of invasion. He underwent EMR which was complicated by rectal perforation. To repair the perforation, an over-the-scope clip was successfully placed and there were no further complications. Pathology of the resected rectal mass confirmed gastric heterotopia, without evidence of atypia or malignancy.
Discussion: Heterotopic gastric mucosa of the rectum is a rare clinical entity that may present asymptomatically or with painless rectal bleeding. Although still disputed HGM in the rectum most probably occurs as a result of erroneous differentiation of pluripotent endodermal stem cells. Malignancy from HGM lesions is poorly understood and uncommon, although malignancy has been reported. Histopathological examination is the gold standard for diagnosis, even so the use of EUS-FNA to observe histological features can be utilized to confirm the diagnosis. There are no current treatment guidelines, but common treatment practices include a proton pump inhibitor or H2 receptor blocker for gastric acid secretion suppression and resection of the HGM lesion.
Figure: Heterotopic gastric mucosa found in the rectum on screening colonoscopy. A - A 12 mm polypoid lesion was found in the rectum. The lesion was umbilicated and in the center multi-lobulated. This was biopsied with a cold forcep for histology. B - An oval intramural (subepithelial) lesion was found in the rectum. The lesion was encountered at 5 cm (from the anal verge). The lesion was non-circumferential and located predominantly at the posterior rectal wall. The lesion was hypoechoic and homogenous. Sonographically, the origin appeared to be within the submucosa (Layer 3). The lesion also involved the following additional wall layers: luminal interface/superficial mucosa (Layer 1) and deep mucosa (Layer 2). The lesion measured up to 7 mm in thickness, and 19 mm in diameter. The endosonographic borders were well-defined. An intact interface was seen between the lesion and the muscularis propria (Layer 4), adjacent structures, internal and external anal sphincter muscles, urinary bladder, prostate and seminal vesicles bilaterally suggesting a lack of invasion. C - Colon, rectum polyp, biopsy: Polypoid colonic and minute squamous mucosa (anorectal junctional mucosa) showing gastric type mucosa with foveolar epithelium metaplasia. Negative for malignancy. Findings are consistent with heterotopic gastric mucosa.
Ethan Chambers indicated no relevant financial relationships.
Sarah Zubair indicated no relevant financial relationships.
Neeraj Anand indicated no relevant financial relationships.
Naveen Anand indicated no relevant financial relationships.
Deborah August indicated no relevant financial relationships.
Ethan Chambers, MD1, Sarah Zubair, MD2, Neeraj Anand, MD2, Naveen Anand, MD2, Deborah August, MD2. P1631 - Hypertrophic Gastric Mucosa: A Rare Finding on Screening Colonoscopy, ACG 2023 Annual Scientific Meeting Abstracts. Vancouver, BC, Canada: American College of Gastroenterology.