Ectopic pancreas and foveolar hyperplasia in a newborn: a unifying etiopathogenesis for gastric outlet obstruction.

Abstract

Gastric outlet obstruction in infants usually is attributable to infantile hypertrophic pyloric stenosis (IHPS). Rare causes, such as foveolar hyperplasia (FH) (1–3) or ectopic pancreas (4,5), have been reported. In this case we describe a newborn infant with gastric outlet obstruction related to coexisting ectopic pancreas and FH who was being treated with prostaglandin (PG) E1. A unifying etiopathogenesis for gastric outlet obstruction is proposed. CASE REPORT A 21-day-old male infant, born at term after an uneventful pregnancy, had persistent postprandial nonbilious vomiting. He had a high anorectal malformation that initially was treated with a diverting colostomy. He had a nonfunctioning left kidney and tetralogy of Fallot with pulmonary atresia. Physical examination and laboratory studies did not reveal the source of his vomiting. There was no peripheral eosinophilia. From the second day of life he had been treated with prostaglandin to maintain patency of the ductus arteriosus. At 14 days of life, a Blalock Taussig anastomosis was performed and prostaglandin infusion was suspended. He received a total dose of 2,799 μg of prostaglandin E1. Abdominal ultrasonography did not confirm the clinical suspicion of IHPS. An upper gastrointestinal contrast study revealed gastric outlet obstruction with no features suggestive of IHPS. Esophagogastroduodenoscopy demonstrated a prepyloric sessile umbilicated mass resembling an ectopic pancreatic rest. A transpyloric feeding tube was left in place with the expectation that obstructive symptoms would resolve; however, every attempt at oral feeding was followed by vomiting. A laparotomy and partial gastrectomy was performed on day 40 of life. The postoperative course was unremarkable. Histologic examination revealed ectopic pancreatic tissue (with endocrine, exocrine, and ductal components) and foveolar hyperplasia (Fig. 1).FIG. 1.: Prepyloric mass: (A) foveolar hyperplasia and (B) ectopic pancreatic tissue.At 10 months of age, a posterior sagittal anorectoplasty was performed, followed by colostomy closure. With 28 months of follow-up, he is symptom free and awaiting definitive repair of his cardiac lesions. DISCUSSION A rare condition in the newborn, gastric outlet obstruction has been ascribed to various causes (1–3). The coexistence of ectopic pancreas and FH in the current case, along with the reported associated abnormalities reported in the English literature, provides an opportunity to better understand the etiopathology of gastric outlet obstruction. Ectopic pancreas is defined as pancreatic tissue with no anatomic and vascular continuity with the pancreas gland itself. It occurs most commonly in the stomach, duodenum and jejunum (4,5). When found in the prepyloric location it rarely causes symptoms. Occasionally it produces complications such as obstruction, hemorrhage, inflammation, or malignant transformation (5). FH is characterized by thickening of the gastric mucosa with foveolar elongation and dilatation. It has been associated with prostaglandin infusion therapy (2,6–8), chronic inflammation (9), and allergic reactions, but some cases remain idiopathic (10). The most common symptoms produced by FH are mild vomiting, diarrhea, abdominal distension and feeding problems. Acute gastric outlet obstruction is an exceptional presentation (6). There has been increasing epidemiologic, clinical, and experimental (7,8) evidence that PGE1 infusion can induce FH in a dose dependent fashion. This very likely occurred in the current case. However, PGE1 mainly affects mucous and HCO3− secreting cells (8). Because exocrine pancreatic tissue has numerous HCO3− secreting cells that are responsive to prostaglandins (11), it seems logical thatmight have induced concurrent PGE1 changes in the prepyloric antral mucosa and in the exocrine component of ectopic pancreas in our patient, both of which contributing to gastric outlet obstruction. The current case also suggests that isolated ectopic pancreas is unlikely to cause gastric outlet obstruction and that a comorbidity should be sought in such cases. In an attempt to find a reasonable explanation for the aforementioned association, we suggest that inflammation played a primary role in the pathogenesis of gastric outlet obstruction (Fig. 2). The previously reported development of pyloric muscle hypertrophy secondary to FH and eosinophilic gastroenteropathy supports this hypothesis (2,12). Although no specific inflammatory mediator can be implicated in smooth muscle hypertrophy, it often occurs in the setting of gastric mucosal inflammation. Whatever the exact inflammatory mediator, it is interesting to observe that even idiopathic IHPS has been related to inflammation. Finally, anecdotal reports documenting pyloric muscle hypertrophy secondary to transpyloric feeding tubes (13), hyperplastic antral polyps (14), and juxta pyloric cysts (15) might be explained by local inflammatory changes induced by mechanical trauma.FIG. 2.: Proposed unifying etiopathogeny for gastric outlet obstruction.Conservative management of FH may include stopping prostaglandin therapy and inserting a nasojejunal feeding tube with the expectation of spontaneous regression. As our case illustrates, however, such an approach is not always effective. Others advocate that surgical excision may be an appropriate therapy for this condition even when it is an incidental finding, to prevent the aforementioned complications (5). In the current case, relief of obstruction was only obtained after surgical resection of the ectopic pancreatic tissue.