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Annular pancreas is a rare congenital anomaly in which pancreatic tissue encircles the duodenum to varying degrees, potentially causing luminal narrowing and functional obstruction. The condition results from abnormal rotation of the ventral pancreatic bud during embryogenesis and may remain unrecognized in many individuals. Some patients experience abdominal pain, postprandial vomiting, or pancreatitis, particularly when duodenal compression becomes clinically significant. Modern diagnostic tools, including cross-sectional imaging and endoscopic retrograde cholangiopancreatography, enhance visualization of the encircling tissue, though diagnostic challenges may persist when symptoms fluctuate. Management depends on the severity of obstruction and associated complications, with surgical bypass procedures serving as the primary intervention for patients requiring definitive treatment. Early recognition and thoughtful evaluation support preservation of long-term gastrointestinal function. The educational activity strengthens participants’ understanding of embryology, pathophysiology, and the clinical presentation of annular pancreas. Learners acquire skills to select appropriate imaging modalities, differentiate asymptomatic from symptomatic cases, and identify complications such as duodenal obstruction or pancreatitis. Collaboration among clinicians, radiologists, gastroenterologists, surgeons, nutrition specialists, and nursing staff is highlighted, thereby enhancing diagnostic accuracy, informing procedural planning, and promoting patient safety. Objectives: Create individualized, evidence-based management strategies that incorporate symptom severity, anatomic findings, and long-term gastrointestinal function goals. Determine the appropriate diagnostic evaluation approach for a patient with annular pancreas. Implement the currently available treatment options in the management of annular pancreas. Collaborate with the interprofessional team on strategies for improving care coordination to improve outcomes in patients diagnosed with annular pancreas. Access free multiple choice questions on this topic.

Annular pancreas is a rare congenital anomaly that is present in less than 1% of the population and is characterized by partial or complete circumferential encasement of the second part of the duodenum by a band of pancreatic tissue during embryogenesis.[1][2] This band is usually located above the papilla of Vater in approximately 85% of diagnosed cases.[3] Results from older studies have reported a prevalence of annular pancreas of 3 of 20,000 autopsies and 3 of 24,519 surgical cases.[4][5] With the advent of newer, more advanced diagnostic modalities, this condition is increasingly recognized. Many individuals with this anomaly remain asymptomatic throughout their lifetime and are often diagnosed incidentally on imaging or during autopsies. However, a subset of patients with annular pancreas may present with clinical manifestations early in life or in adulthood, typically between 20 and 50 years of age.[6][7][8] Based on the morphologic distribution of pancreatic tissue, annular pancreas has been classified into a complete or incomplete type. Complete type annular pancreas shows pancreatic parenchyma or annular duct completely encircling the second part of the duodenum, confirmed by macroscopic inspection, and incomplete type annular pancreas demonstrates partial circumferential encasement of the duodenum by pancreatic tissue, confirmed by endoscopic retrograde cholangiopancreatography (ERCP) or surgical evaluation.[9] The annular pancreatic duct (APD) commonly drains into the central pancreatic duct (MPD). Still, it can communicate with the intrapancreatic common bile duct (CBD), the duct of Santorini, or the duct of Wirsung.[10] Yogi et al classified annular pancreas into 6 subtypes, with type I demonstrating communication of APD with the duct of Wirsung and type II showing the duodenum encircled by MPD. Types I and II are the most common subtypes, with the other 4 subtypes less frequently encountered and corresponding to the APD communicating with the duct of Santorini or the CBD.[11]

Given the rarity of this congenital condition, the precise etiology of annular pancreas development is not well defined, but it is considered an embryopathy.[6] During the first 4 to 8 weeks of embryonic development, the pancreas normally develops following rotation and fusion of the dorsal and ventral pancreatic buds as a result of the expansion of the duodenum. The ventral bud develops into the inferior part of the head and the uncinate process of the pancreas, while the dorsal bud develops into the body and tail of the pancreas.[9][12] The development of annular pancreas is proposed to be a migration anomaly resulting from the failure of the ventral bud to rotate and extend to encase the second portion of the duodenum either partially or completely.[9][12] Several theories, some dating back to the 1900s, have been proposed to explain the formation of an annular pancreas, but none have gained predominance. However, immunohistochemistry studies have shown that the annular pancreas arises from the ventral pancreatic anlage.[8] Although not well studied, the role of genetic factors in this anomaly has been linked to isolated case reports of familial annular pancreas and to overexpression of the ventral-specific gene transmembrane 4 superfamily member 3 (tm4sf3).[13]

The true prevalence of annular pancreas is currently unknown owing to the rarity and infrequent reporting of this congenital anomaly. Before the availability of contemporary imaging, this anomaly was noted incidentally in 3 of 20,000 autopsies and in 3 of 24,519 individuals who underwent abdominal surgeries.[4][5] With the availability of novel imaging modalities, the prevalence of annular pancreas has increased marginally to approximately 1 in 1000 cases.[14][15][16] Annular pancreas affects both sexes with a slight male preponderance, which has been a contentious issue.[17][18] Annular pancreas accounts for 30% of congenital duodenal obstructions in newborns.[19]

The pathophysiology of annular pancreas is explained by the direct impact of the migratory defect during embryogenesis. Duodenal obstruction is secondary to a mechanical defect, which can be extrinsic from the encasement of the duodenum or intrinsic from scarring, stenosis, or the presence of duodenal webs. The pathogenesis of pancreatitis in annular pancreas is unclear. Pancreatitis, when it occurs, is usually confined to the annulus and the adjoining pancreatic head, sparing the body and tail of the gland, which is likely secondary to fibrosis that prevents pancreatic secretions from passing through the annular duct and increases the intrinsic susceptibility of the annular pancreatic tissue to damage.[20][21][22] Peptic ulcer disease may be related to gastric stasis and antral overdistension with resulting hypergastrinemia.[8][23] Biliary ductal dilation is likely due to the progression of chronic pancreatitis, leading to fibrosis or ductal compression by the annular gland.[9]

Microscopic examination of the annular pancreatic tissue demonstrates the presence of many pancreatic polypeptide cells of the ventral pancreatic anlage arranged in irregularly shaped islets.[24] Histologically, annular pancreas has been classified into 2 types: intramural and extramural, on the basis of pancreatic tissue within the duodenal wall. The extramural type exhibits the presence of a ventral pancreatic duct encircling the duodenum, and the intramural type reveals the presence of pancreatic tissue woven into the duodenal wall with evidence of small ducts draining into the duodenum.[23]

Clinical manifestations of annular pancreas can occur at any age, from infancy to adulthood, and, given its bimodal age distribution, the age of presentation and the degree of duodenal constriction are key factors.[9] Infants with annular pancreas associated with significant duodenal constriction present with nonbilious vomiting, bloating, and feeding intolerance. Other infants with minimal constriction or nonexistent constriction can remain asymptomatic lifelong, and a small fraction can become symptomatic, usually between the third and sixth decade of life, presenting with symptoms of abdominal pain, duodenal obstruction, and pancreatitis, as evidenced by the review of a large case series cohort by SJS Nagpal et al.[1] The other, less common manifestations of annular pancreas in adulthood are peptic ulcer disease and biliary obstruction.[25][26] The association of chromosomal abnormalities in annular pancreas is well known, with trisomy 21 being the most frequently detected anomaly.[27] Many infants with annular pancreas also have various other associated congenital anomalies, including malrotation, tracheoesophageal fistula, esophageal atresia, duodenal atresia, renal anomalies, duodenal diverticulum, pancreas divisum, biliary atresia, anorectal malformations, and congenital heart disease.[6][26][27] In adults with annular pancreas, the most common associated anomalies were pancreatic divisum, malrotation, duodenal webs, and Schatzki ring.[27]

No biochemical or genetic test is available specifically for annular pancreas. The diagnosis of annular pancreas is radiologic and usually made incidentally or on the evaluation of clinical manifestations of annular pancreas. The diagnosis of annular pancreas can be made prenatally, preoperatively, or intraoperatively using a range of noninvasive and invasive diagnostic techniques. Prenatally, an annular pancreas can be diagnosed by prenatal ultrasonography.[27][28] In infants presenting with signs of intestinal obstruction, the diagnosis can be made by ultrasonography or plain abdominal radiographs, which demonstrate the classic “double bubble sign.” However, this is nonspecific for annular pancreas.[29][30] Newer ultrasonographic techniques incorporating upper gastrointestinal saline contrast have been used to improve the accuracy of diagnosing this rare congenital anomaly.[31][32] In adults, the diagnosis is usually made by computerized tomography (CT) imaging or magnetic resonance imaging. A large retrospective case series by SJS Nagpal et al showed that a significant number of patients were diagnosed solely by CT imaging.[1] Other imaging techniques that aid in diagnosing annular pancreas include magnetic resonance cholangiopancreatography, ERCP, and endoscopic ultrasonography.[33][34] Sandrasegaran et al showed that complete encasement of the duodenum by pancreatic tissue is not essential for diagnosing annular pancreas.[9] Newer imaging techniques, including positron emission tomography/CT with the radiotracers C-11 choline and F-18 fluciclovine, have demonstrated the diagnosis of annular pancreas.[35] Despite many advances in diagnostic techniques, the gold standard test for diagnosing annular pancreas remains laparotomy with a thorough gross examination of the duodenum and the head of the pancreas.[27]

Best-practice guidelines for the management of annular pancreas are lacking, and treatment is tailored to each patient's symptoms and complications.[30] Asymptomatic individuals without signs or symptoms of annular pancreas can be observed closely without intervention.[6] Patients presenting with symptoms of acute pancreatitis should be managed with supportive care. Recurrent disabling attacks of acute-on-chronic pancreatitis can be considered for a pylorus-preserving Whipple procedure on a case-by-case basis.[1] Division of the pancreatic annulus is not advised due to the increased incidence of postoperative complications such as pancreatitis, pancreatic fistulas, and duodenal stenosis.[30] Management of symptomatic cases with duodenal obstruction secondary to annular pancreas is purely surgical, with surgical bypass procedures such as gastrojejunostomy, duodenoduodenostomy, or duodenojejunostomy in adults and children.[18][30] In contrast to children undergoing duodenal bypass procedures, Zyromski et al highlighted the complex pancreaticobiliary pathology associated with annular pancreas in the adult population by describing that 20% of adults in their study group requiring surgical intervention underwent complex pancreaticobiliary surgical procedures, which included pancreaticoduodenectomy, lateral pancreatojejunostomy, biliary/pancreatic sphincteroplasty, and bypass of the biliary system.[27]

As the clinical manifestations of annular pancreas exhibit a bimodal age distribution, presenting either early during infancy or adulthood, the differential diagnosis of this anomaly is also based on the age of presentation. Infants commonly present with duodenal obstruction and the classic "double bubble sign" on imaging; the differential diagnosis can be classified into intrinsic or extrinsic causes.[29][36] Intrinsic Causes Duodenal atresia Duodenal stenosis Paraduodenal hernias Meckel diverticulum Duodenal webs (critical intrinsic causes that need to be considered) Extrinsic Causes Malrotation of the gut Midgut volvulus Miscellaneous Causes Peptic ulcer disease Pancreatic divisum Primary duodenal Pancreatic malignancies [37] Gastroduodenal tuberculosis This should be considered in patients from geographical areas endemic for tuberculosis.[38]

The prognosis of annular pancreas in children is excellent, with increased overall survival rates, despite the presence of associated congenital malformations and chromosomal anomalies.[39] This has been attributed to improved neonatal care, nutritional management, early detection, and management of associated anomalies.[26] The prognosis of annular pancreas in adults is favorable if it is not complicated by underlying malignancy.

Complications of annular pancreas are secondary to the mechanical migratory effect of the pancreatic anlage and include: Acute and chronic pancreatitis Common bile duct obstruction Gastric outlet obstruction Peptic ulcer disease Cholecystolithiasis Gastric diverticulum Pyloric stenosis [40][41][42][43]

Deterrence in annular pancreas focuses on early recognition rather than actual prevention, as this congenital anomaly results from incomplete rotation of the ventral pancreatic bud and cannot be avoided through behavioral or environmental modifications. Annular pancreas involves a ring of pancreatic tissue encasing the duodenum and was historically identified during surgery or autopsy, but modern imaging has led to more frequent diagnosis. Although many patients remain asymptomatic, infants may present with duodenal obstruction—manifesting as bilious vomiting or feeding intolerance—while adults may develop abdominal pain, peptic ulcer disease, or pancreatitis. The condition is also associated with chromosomal abnormalities, most commonly trisomy 21. Prompt recognition of these presentations allows early imaging, surgical evaluation, and intervention before complications such as dehydration, malnutrition, or recurrent pancreatitis progress. Patient and family education is central to improving outcomes, reducing anxiety, and supporting timely care. Families should receive clear explanations of the anatomy, associated conditions, and the rationale for surgical management—typically duodenal bypass procedures such as gastrojejunostomy, duodenoduodenostomy, or duodenojejunostomy in children and adults. Education should also address postoperative expectations, including changes in feeding, monitoring for vomiting, abdominal distention, or weight loss, and recognizing signs of obstruction or infection. Adults benefit from guidance on symptom monitoring, dietary strategies during pancreatitis episodes, and when to seek urgent care. Involving surgeons, pediatricians, nutritionists, and genetic counselors when indicated enhances communication, sets realistic expectations, and supports safe recovery and long-term outcomes.

Annular pancreas is a rare congenital anomaly characterized by partial or complete encasement of the duodenum by pancreatic tissue. Although traditionally viewed as a disorder of infancy, evidence shows it occurs with nearly equal frequency in adults and children. Symptoms vary depending on the degree of duodenal constriction and may include duodenal obstruction, abdominal pain, and pancreatitis. Because standardized management guidelines are lacking, care must be individualized based on symptom severity and associated complications.[30] Early detection through advanced imaging and awareness of concurrent anomalies is essential to reduce morbidity and mortality. Optimal management requires a coordinated interprofessional approach involving neonatologists, gastroenterologists, surgeons, radiologists, nurses, dietitians, and pharmacists.[27][44] Effective communication ensures timely diagnosis, nutritional optimization, and surgical planning, particularly when chromosomal or structural anomalies are present. Clinicians must develop diagnostic skills using imaging modalities such as computed tomography and magnetic resonance imaging, apply evidence-based interventions, and coordinate follow-up to monitor adults at risk for neoplasia. This collaborative, patient-centered strategy enhances safety, outcomes, and overall team performance.[27]