Annular Pancreas in Adults Presenting as Chronic Pancreatitis and Duodenal Obstruction: Literature Review and a Case Report

Background: Annular pancreas is a rare congenital anomaly with an estimated incidence of 3.4 per 1,00,000 live births. It is more commonly diagnosed in infants. Its occurrence in adults is exceptionally rare but clinically significant, as seen in our case, where it presented as a duodenal obstruction. Case presentation: We present a case of an adult male who presented with a 3-week history of projectile bilious vomiting associated with postprandial abdominal pain and early satiety. Imaging studies revealed a segment of the pancreas encircling the second part of the duodenum, along with pancreatolithiasis. Based on the diagnosis of annular pancreas with chronic calcific pancreatitis, the patient underwent pylorus-preserving pancreatoduodenectomy. Materials and Methods: A structured literature review was performed using PubMed and Scopus databases, covering the period from 2018 to 2024. A total of 24 case reports were analyzed. Results: The review confirms that annular pancreas remains a rare condition, often undiagnosed in asymptomatic individuals with abdominal pain (83.3%) and vomiting (41.6%) as the most common symptoms. The most common diagnostic modality is the CT scan (computed tomography), at 64.1%, and surgical procedures, such as gastrojejunostomy, are the most common treatment modality, at 46.5%. Conclusions: It is a rare congenital condition that usually remains undiagnosed in asymptomatic individuals but typically presents with abdominal pain and vomiting when symptomatic. Diagnosis relies primarily on CT imaging. Conservative management is preferred for asymptomatic cases, and surgery is for symptomatic patients. Further research is needed to develop standardized management protocols.