Heterotopic pancreas causing duodenal obstruction in a patient previously treated for choledochal cyst.

A 9-year-old boy presented with duodenal pancreatic rest causing obstruction and required surgical intervention. He had been treated at the age of 4 months for a choledochal cyst. Both choledochal cyst and heterotopic pancreas are entities that are commonly encountered in children, but the incidental presence of both the entities in the same child, albeit presenting metachronously, is extremely rare.

INTRODUCTION

The presence of pancreatic tissue outside its normal localization and without anatomic and vascular continuity with the normal pancreas is termed heterotopic pancreas (HP); pancreatic rests, ectopic, aberrant, or accessory pancreas are the other terms to describe the entity. HP may occur throughout the gastrointestinal tract, but has a propensity to affect the stomach, duodenum, jejunum, Meckel's diverticulum, and ileum. Less frequently, it is observed in the liver, gallbladder, bile duct system, and papilla of Vater.[1] HP is known to be associated with various associated anomalies like malrotation, small intestinal atresias, biliary atresias, congenital diaphragmatic hernias, Meckel's diverticuli, annular pancreas and esophageal atresias.[23] There have been isolated case reports of the presence of HP within the choledochal cyst (CC).[45] Association of jejunal HP with CC has also been reported once.[6]

CASE REPORT

A 9-year-old boy presented with features of gastric outlet obstruction for 1 month. He was operated for CC type 1 at the age of 4 months at the same center; complete excision of cyst with Roux-en-Y hepaticojejunostomy was done. Magnetic resonance cholangio-pancreaticography (MRCP) done prior to first surgery had shown pancreaticobiliary malunion (PBMU), CC and dilated pancreatic duct, suggestive of chronic pancreatitis [Figure 1]. No annular pancreas or obvious pancreatic rests were noted at the MRCP or subsequent surgery. Abdominal examination revealed fullness in epigastric region; reverse gastric peristalsis was noted. Upper gastrointestinal (GI) contrast study revealed partial obstruction of the first part of duodenum [Figure 2]. Upper GI endoscopy revealed the lumen of first part of the duodenum completely obliterated by a large polypoidal mass; the endoscope could not be negotiated beyond the first part of duodenum.

Figure 1

Magnetic resonance cholangio-pancreaticography showing pancreaticobiliary malunion, type I CC and dilated pancreatic duct

Figure 2

Upper gastrointestinal contrast study showing near-total obstruction of first part of duodenum

On exploration, the first part of duodenum was found to be severely inflamed and thickened with near complete obliteration of its lumen. The Roux-en-Y loop of the previous hepaticojejunostomy was 5 cm away from the duodenal lesion. Excision of 2.5 cm of distal stomach, pylorus and first part of duodenum with gastroduodenostomy akin to Billroth I procedure was done. Histopathologic examination of the entire excised specimen revealed transmural acute on chronic inflammation and diffuse fibrosis. There were submucosal heterotopic pancreatic rests in the excised duodenum, though there were no abnormal cells in the excised pylorus and the stomach [Figure 3]. The postoperative period was uneventful. The child is doing well at 10 months follow-up.

Figure 3

Heterotopic pancreatic rests in the submucosa of the duodenal partition (H and E, × 40)

DISCUSSION

The etiology of HP is unknown.[7] The proposed theory is that during rotation of foregut in a fetus and fusion of dorsal and ventral parts of pancreas, small islands of pancreatic rests are carried away and continue to develop at this aberrant location.[8] HP is seen in 1–2% of patients as autopsy findings and 1 in 500 of upper abdominal surgeries.[9] Macroscopically, it may appear as 1–4 cm yellow nodular structures. Our case was considered to be a type 2 ectopic pancreas, based on Heinrich classification.[10] Majority of the patients with HP are asymptomatic. However, they may present with obstruction, lump, GI bleeding, etc., depending on the size and location of HP.

Correct preoperative diagnosis is usually not possible and the eventual diagnosis is made on surgical exploration and pathological examination. Clinically significant lesions are greater than 1.5 cm in maximum diameter and are adjacent to or directly involve the mucosa.[11] Ulceration may give a crater-like or volcanic appearance on endoscopy.[7] Pancreatitis, malignant transformation and pseudocyst are amongst the less common but documented complications.[12] Upper GI obstruction as seen in our patient is common with HP. But most of the cases of HP causing gastric outlet syndrome have been described in adults. Such an occurrence has been occasionally reported in children and rarely reported in infants and neonates too.[1314]

Radiological investigations like computed tomogram (CT) scans, endoscopic ultrasonograms and nuclear scan studies assist in preoperative diagnosis, but with difficulty.[15] Upper GI endoscopy, though helpful in certain patients presenting with submucosal nodules, was not helpful in the preoperative diagnosis in our case. Hence, the diagnosis is prominently intraoperative or based on histology.[15] Therefore, surgery is frequently needed to make a definitive diagnosis and plan further management and also because differential diagnosis includes leiomyomas, lymphomas, carcinoid tumors, gastrointestinal stromal tumors (GIST) and other malignancies. On review of available literature on HP, we found that all the pathologies known to affect the pancreas can also be seen in HP. Pre-operative diagnosis of the exact cause can also be extremely difficult. Hence, we feel that whenever HP is encountered incidentally or because of complication, it warrants excision. Keeping this in mind, we performed the excision of the lesion rather than a simple bypass such as posterior gastrojejunostomy.