Asymptomatic heterotopic pancreas in Meckel’s diverticulum: a case report and review of the literature

The aetiology of HP, otherwise known as “aberrant”, “ectopic”, or “accessory” pancreas, is still unclear, but it is believed to arise embryonically during rotation of the foregut and fusion of the dorsal and ventral pancreatic buds. Some tissue separates from the pancreas and develops into HP in any portion of the alimentary system. Another best known theory is based on the pancreatic metaplasia of endodermal tissue [4,5]. Because of the proximity of the embryonic pancreatic primordial buds and the foregut during development, it is not surprising that 70 to 90% of ectopic pancreas occurs in the upper gastrointestinal system [9]. MD is the second most common site of heterotopic tissue; the stomach is the most common site (50 to 60% of cases) while 5 to 16% of cases occur in the pancreas [9]. Surgical excision is the first and best choice of treatment because medical treatment is not effective [5]. However, the treatment of HP depends on the patient. Asymptomatic patients with a positive diagnosis must remain under medical supervision and be reviewed periodically. Symptomatic patients without complications should have their lesions excised, preferably by local resection. In sites accessible by fibrescope, endoscopic removal may be performed. HP found during surgical procedures motivated by other diseases, as in our case, should be excised and submitted for a frozen section study whenever necessary, thus avoiding possible complications and the need for reoperation. In cases of lesions associated with bleeding, obstruction or suspicion of malignancy, an appropriate surgical approach is undertaken [9]. HP can be eliminated by simple excision, as multiple lesions are unusual [11]. The preoperative diagnosis of HP in the small intestine is difficult. Symptoms depend on the size of lesion and involvement of mucosa. On clinical examination, significant lesions are greater than 1.5cm [7,9]. Most cases represent HP in a MD with gastrointestinal bleeding (Table 1), but in our case it was asymptomatic. Because HP can be found submucosally and the most common submucosal tumour is gastrointestinal stroma tumour (GIST), HP can frequently be mistaken as GIST or leiomyoma at endoscopy, ultrasonography or CT scanning [12]. In our case, HP was mistaken for metastasis of the caecal tumour. The definitive diagnosis is confirmed by pathological examination after the resection (Table 2). However, endoscopic ultrasound findings are often associated with these lesions: a diameter larger than 4cm, poorly defined margins, cystic spaces and internal echogenic foci, and adjacent lymphadenopathy and rapid growth [13]. Although, pathological examination is the most accurate diagnostic method for diagnosis of ectopic pancreas, most biopsies are inconclusive, because it is difficult to take adequate tissue samples. MD can be diagnosed with ^99mtechnetium pertechnetate scintigraphy, which detects ectopic gastric mucosa in MD. However, the diagnostic accuracy of this method is 46% in adults. Abdominal ultrasound, X-ray and CT usually give nonspecific findings. MD can be detected by capsule endoscopy or double-balloon enteroscopy. The diagnosis of MD with HP is difficult [6,14]. Management of incidentally found MD is controversial. Some authors suggest that indications for diverticulectomy should be based on intraoperative findings. Wide-mouthed, thin-walled diverticula without bands could be left undisturbed, whereas thickened, narrow-based diverticula should be resected. However, there are no definite anatomic criteria to predict the probability of future complications. According to the literature, the benefits of incidental diverticulectomy outweigh its attending morbidity and mortality [15]. In our case, MD was resected because ectopy of the pancreatic tissue was considered a metastasis of the caecal tumour.