Introduction

Ectopic gastric mucosa has been described at various locations in the body including the mouth, esophagus, duodenum, pancreas, biliary system, small bowel, mediastinum, scrotum, bladder, and spinal cord (₁). Nevertheless, gastric heterotopia of the rectum is a rare finding, with only 40 cases reported in the literature to date. We describe a case of gastric heterotopia in the rectum and review the potential manifestations, likely etiologies, and diagnostic pitfalls for this unusual biopsy finding.

Case Report

A 34-year old female presented with altered bowel habits, abdominal bloating, excessive “intestinal noise,” visible abdominal distention, and occasional nausea. She denied any rectal bleeding, and had no family history of colon cancer. The patient had undergone a colonoscopy approximately four years prior secondary to irritable bowel syndrome complaints. The colonoscopic examination was normal at that time.

Colonoscopic examination at the current presentation revealed the colonic mucosa to be normal. A single non-bleeding smooth polyp, described as salmon in color, was seen in the rectum that measured 1.5cm. The affected area was slightly raised, sessile, and well circumscribed. There appeared to be some furrowing within this “polyp”. Dyes were not originally applied, and magnification endoscopy unavailable. This polyp did not involve the anal verge and showed no stigmata of recent hemorrhage (Figure 1).

Figure 1

Figure 1: Colonoscopic view of a single large sessile polyp seen in the rectum (arrows delineate the polyp).

Multiple biopsies were obtained and sent for pathologic examination. On retroflexed view, other than the polyp, the examination was unremarkable.

Pathologic Findings

The fragmented polyp was received in formalin and measured 1.4 x 1 x 0.5 cm in aggregate. Paraffin embedded tissue was sectioned at 5 microns and multiple levels were evaluated with routine hematoxylin and eosin stain. Benign fundic-type gastric mucosa was present on microscopic examination (Figure 2).

Figure 2

Figure 2: Fundic-type gastric mucosa in a rectal biopsy (hematoxylin and eosin, 40x)

No colonic mucosa was identified. No dysplastic epithelium was identified. A Warthin-Starry stain highlighted Helicobacter-like organisms located on the surface of the gastric-type mucus cells (Figure 3).

Figure 3

Figure 3: H. pylori like organisms on surface of mucosal cells (warthin starry, 400x)

Discussion

Rarely does the histologic evaluation of a colorectal polypectomy specimen reveal heterotopic gastric mucosa. Heterotopic gastric mucosa in the rectum has only been described in 40 published reports, usually presenting as small sessile polyps. Vieth et al reported that peptic lesions or repeated mechanical manipulation may “displace” heterotopic gastric glands into the submucosa in a pseudoinvasive manner (₂). However, the clinical history of our patient was unremarkable regarding prior rectal injury.

Review of the literature through 2006 contains 40 cases of gastric heterotopia of the rectum. The first case of gastric heterotopia of the rectum was reported by Ewell and Jackson in 1939 (₃). The lesion was found to be more common in males than females, with an average age at presentation of about 21 years (₄). The most common symptom at presentation was painless rectal bleeding, with abdominal pain and diarrhea also being reported. The heterotopic tissue was frequently located in the posterolateral region of the rectum, between 5 and 8cm from the anal verge (₅). This patient did not report any bleeding per rectum, but instead presented with symptoms of irritable bowel syndrome.

Embryologic development of the esophagus and stomach occurs at approximately the fourth week of gestation. During this period, the esophagus develops as the foregut is divided into the ventral respiratory portion and the dorsal esophageal portion. Subsequently, the stomach appears as a fusiform dilatation of the foregut and its appearance changes as various regions of its wall grow at different rates. The stomach also rotates as the position of the surrounding organs is determined. Developmental errors in this formation from failure of these structures to develop correctly can be implicated in instances of gastric heterotopia in the foregut, where it is most frequently seen in the esophagus (₆).

Although there is no agreement regarding the origin of the gastric tissue found at these ectopic sites, a few theories have been postulated. It has been suggested that congenital gastric heterotopia results from an error during fetal development in the differentiation of pluripotent endodermal stem cells (₄). This theory is supported by the immunocytochemical studies of Carlei et al. who demonstrated that the metabolic and functional activity of gastric heterotopic mucosa regarding the production of acid and mucin is identical to that of the normal stomach (₁, ₇). Another theory detailing a congenital origin involves the failure of the developmental descent of the fetal foregut. In contrast, other authors suggest that gastric heterotopia is an acquired condition, similar to Barrett's esophagus, whereby abnormal regeneration of the mucosal cells after trauma or a destructive process results in metaplasia (₄).

Helicobacter pylori (H. pylori) may colonize gastric mucosa wherever it is found in the alimentary tract, and the manifestations of infection, including ulceration and bleeding, may be similar to those seen in the stomach. Dye et. al. reported a case of rectal gastric heterotopia, positive for H. pylori by histochemical stain, found to be actually colonized with organisms (₈). This finding supports the possibility that H. pylori may pass along the gastrointestinal tract in a viable form. Kestemberg et. al. felt that the findings of H. pylori organisms in a typical distribution on the surface of the gastric-type mucus cells in the rectum gives strength to the theory that the bacteria may be eliminated in the feces (₁). A warthin-starry histochemical stain of our biopsy highlighted a few rod-shaped organisms that had morphologic features consistent with H.pylori. A biopsy of the patient's gastric antrum obtained at the same time showed only scattered chronic inflammatory cells within the lamina propria and a special stain for H. pylori was negative. Despite these results, H. pylori infection cannot be ruled out as this biopsy represents only a limited area of the stomach. Given the negative pathology results, additional confirmatory testing (such as the sensitive urease breath test or H. pylori stool antigen test) was not done. Nevertheless, this finding provides additional evidence that the organisms may in fact be passed with feces and contribute to the ulceration and bleeding commonly seen in these cases.

Identification of the gastric mucosa is usually made on biopsy, as it would be difficult to identify the gastric mucosa prior to the development of a visible abnormality by direct visualization. In many of the cases cited, the symptoms had been present for many years, and the patients underwent extensive work-up prior to diagnosis (₅). Surgical excision or polypectomy is the preferred treatment modality, with complete symptomatic relief occurring in most cases following excision. Since this type of lesion can occur anywhere in the alimentary tract, long-term follow-up is recommended for all patients (₉). In this case, endoscopic mucosal resection (EMR) was not done as this was felt to be a benign condition and there is no established recommendation for removal. Instead, the patient is to be followed with periodic flexible sigmoidoscopies. Since this is such a rare case and there are no guidelines, it is uncertain whether it needs to be removed or simply just followed. Furthermore, it is unclear whether there is increased malignant potential. EMR will be discussed with the patient on a follow-up visit.