Duodenal duplication is a rare congenital disorder and accounts for only 5% to 7% of all gastrointestinal duplications . They are mostly limited to the first or second part of the duodenum usually adjacent to the pancreatic surface sharing a common wall and blood supply with the duodenum. The common clinical presentation in children is vomiting, abdominal pain, or abdominal mass. Acute pancreatitis has been reported in a few cases as a rare complication  and hemorrhagic ascites in one case report . To the best of our knowledge, this is the first reported case of combined recurrent acute pancreatitis and hemorrhagic ascites caused by duodenal duplication in a child.
There are several possible mechanisms for pancreatitis to develop from a duplication cyst . In this case, the duodenal duplication cyst most probably caused mechanical obstruction of the pancreatic duct and subsequent acute pancreatitis, given the fact that the initial ultrasonography confirmed pancreatic duct dilatation. The non-communicating cyst may produce viscid mucous secretions and mucosal inflammation which may cause distention of the cyst and obstruction of the pancreatic duct . We do not think that gallstones contributed to acute pancreatitis in our case, because no gallstones were identified on multiple imaging studies. The sand-like stones found in the gallbladder were probably due to long-term fasting and somatostatin. Ascaris infestation is probably an incidental finding rather than a cause for acute pancreatitis, because thorough examination during surgery did not find any adult Ascaris in the pancreaticobiliary system. We speculate that hemorrhagic ascites may have been the result of mucosal inflammation, necrosis and micro-perforation of the duplication cyst. Acute necrotizing pancreatitis can cause ascites but would be an unlikely cause of the hemorrhagic ascites in our case because neither imaging studies nor exploratory laparotomy revealed a necrotic pancreas.
Multiple reports found that both CT imaging and MRI can adequately identify a duodenal duplication cyst [3, 6]. However, due to the rarity of duodenal duplication cyst and lack of clinical experiences, more common lesions such as pancreatic pseudocyst are often suspected. In fact, duodenal duplication cyst was reported to mimic pancreatic cyst in a patient with acute pancreatitis . Kawahara et al.  found 25 children with duodenal duplication presenting as pancreatitis. In 10 cases, the duodenal duplications were not in continuity with the duodenum and the locations of the duplications were variable. Six were within the pancreas: four in the pancreatic head, one in the aberrant lobe connected with the main pancreatic lobe, and one in the pancreatic tail. Of interest, a pancreatic pseudocyst was associated with the duodenal duplications in eight of the 25 reported cases. Abdominal CT and abdominal ultrasound were the most frequently used diagnostic tests in the reported cases . In our case, both CT and MRI images showed a well-delineated cystic lesion located between the descending portion of the duodenum and the head of pancreas. However, duodenal duplication was never suspected, probably due to the severity of pancreatitis and accompanying hemorrhagic ascites. The upper gastrointestinal endoscopy did not help in our case because the cyst was non-communicating with either duodenum or stomach. An abdominal ultrasonography failed to reveal any cystic lesion in our case.
The surgical intervention for duodenal duplication cyst includes complete or partial surgical resection of the cyst. The location of the cysts in relation to the duodenum, especially to the ampulla, is important to determine the treatment strategy [3, 6, 8]. Alternatively, duodenum duplication can be safely and effectively treated by different endoscopic interventions [3, 9]. Antaki et al.  reported that eight patients were treated with endoscopic incision and marsupialization for symptomatic intraluminal duodenal duplication cysts. All patients remained asymptomatic at a median follow-up of 7.3 years. Although a duodenal duplication cyst is considered a benign clinical entity, three cases with development of malignancy have been reported . Therefore, a long-term follow-up would be necessary for patients who had undergone partial resection of a duodenal duplication cyst.