We present the case of a 28-year-old female referred via the 2-week-wait colorectal cancer pathway for urgent colonoscopy following episodes of significant rectal bleeding with passage of large blood clots. She described fluctuating bowel habits with a baseline tendency toward constipation, intermittent watery stools, and tenesmus associated with bleeding episodes. Additional symptoms included bloating, fatigue, and nausea. She denied urgency, mucus discharge, weight loss, or systemic symptoms. Her past medical history was unremarkable; she was a non-smoker, took no medications, and had a WHO performance status of 0. Routine blood tests, including haemoglobin and iron studies, were normal, and no FIT test had been performed.

Colonoscopy demonstrated a solitary 15 mm Paris IIa flat-elevated lesion in the rectum, exhibiting a JNET type 1 and Kudo type I pit pattern. En bloc resection was performed using submucosal lift and hot snare polypectomy. The remainder of the colonoscopy was unremarkable. Histopathological analysis of the resected specimen demonstrated gastric heterotopia composed of fully differentiated gastric mucosa without dysplasia or features of neoplasia.

Gastric heterotopia is defined as the presence of mature gastric mucosa outside its normal anatomical location. It is most commonly found in the upper gastrointestinal tract, and its occurrence in the colon, particularly in the rectum, is exceedingly rare¹. Although often asymptomatic, gastric heterotopia can be clinically significant due to local acid secretion, which may lead to ulceration, bleeding, mucosal irritation, and, in rare cases, stricture formation².

Rare complications reported in the literature include chronic inflammation, polyp formation, and although extremely uncommon, dysplastic change. Although rare, dysplasia has been identified in around 4–5% of rectal gastric heterotopia cases in the literature, highlighting the importance of thorough evaluation and definitive resection³. Endoscopic resection is considered the treatment of choice, offering both definitive diagnosis and resolution of symptoms. In this case, complete resection was achieved, thereby eliminating the risk of further bleeding and avoiding the need for additional therapy.

This case emphasizes the importance of maintaining a broad differential diagnosis in young patients presenting with alarming lower gastrointestinal symptoms, as uncommon benign conditions such as gastric heterotopia may mimic more serious pathology. Accurate endoscopic assessment combined with histological confirmation remains central to appropriate management.