Annular Pancreas

Annular pancreas is a congenital ring of pancreatic tissue encircling the second part of the duodenum.

• Incidence 1 in 12,000 to 15,000 live births; due to abnormal migration of the ventral pancreatic bud.
• Associated anomalies: Down syndrome (trisomy 21), duodenal atresia or stenosis, malrotation, cardiac defects, tracheo oesophageal fistula, biliary anomalies, pancreas divisum.
• Neonatal presentation is with duodenal obstruction; adult presentation occurs in 50% of diagnosed cases (30 to 60 years).
• Complications: duodenal obstruction, peptic ulcer, pancreatitis, biliary obstruction, jaundice, rarely carcinoma.

• Neonates: bilious vomiting (75%), feeding intolerance, polyhydramnios prenatally, upper abdominal distension.
• Adults: postprandial fullness, nausea, vomiting, epigastric pain, weight loss, recurrent pancreatitis, peptic ulcer disease.
• Many are asymptomatic and incidentally detected.
• Jaundice if the ring involves the distal common bile duct.

• Prenatal ultrasound: polyhydramnios and "double bubble" sign.
• Neonatal abdominal radiograph: double bubble sign (gas in stomach and proximal duodenum) with reduced distal gas (complete obstruction in atresia).
• Upper gastrointestinal contrast study: duodenal narrowing with dilated proximal bowel.
• CT and MRI/MRCP: pancreatic tissue encircling the descending duodenum, ductal anatomy (the duct of the ring may join the main or accessory duct).
• Endoscopy: extrinsic compression with ulcer or stenosis in adults, ERCP for ductal anatomy.
• Screen for associated anomalies (echocardiography, karyotype).

• Neonates: nasogastric decompression, IV fluids, correct electrolytes, then surgical bypass with duodenoduodenostomy (diamond shaped anastomosis) or duodenojejunostomy. Never divide or resect the annular pancreas because of pancreatic fistula and pancreatitis risk.
• Adults with obstruction: duodenoduodenostomy or Roux-en-Y duodenojejunostomy (open or laparoscopic), with excellent outcomes; gastrojejunostomy is a less preferred alternative because of ulcer risk.
• Asymptomatic: observation.
• Pancreatitis: supportive care, treat as per cause; endoscopic sphincterotomy or ductal stenting in selected cases.
• Peptic ulcer: proton pump inhibitor and Helicobacter pylori eradication.
• Perioperative cefazolin and nutritional support.
• Follow up for anastomotic function and pancreatic complications.