Complete agenesis of the dorsal pancreas

A 28-year-old male, presented with complaints of right lower abdominal pain associated with an episode of vomiting. There were no other associated symptoms. He does not have any other associated symptoms or history of any relevant illness in the past. Physical examination and routine laboratory examination was unremarkable.

Ultrasound examination with the curvilinear probe placed in the epigastrium showed the normal head of pancreas with absent neck, body and tail of pancreas. Contrast-enhanced computed tomography (CECT) of the abdomen and Curved axial multiplanar reformatted (curved MPR) images showed normal head and uncinate process of the pancreas, with completely absent neck, body and tail of the pancreas. The proximal small bowel loops were visualized in pancreatic bed anterior to splenic vein described as dependent intestine sign. No evidence of any surgical clips in pancreatic bed.  Oblique coronal minimum intensity projection (MinIP) images showed normal course of intrapancreatic portion of distal common bile duct (CBD) with absent dorsal duct. No evidence of any pancreatic parenchymal masses, calcification, duct calculus. No imaging features of pancreatic or peripancreatic inflammation.

Agenesis of dorsal pancreas is an anomaly in development of the pancreas, however, the complete agenesis of dorsal pancreas is an extremely rare anomaly. The human pancreas develop from foregut, it begins with a dorsal bud followed by two ventral buds. The left ventral bud regresses, while the right ventral bud starts to migrate posterior upon gut rotation and finally fuses with the dorsal pancreatic bud. The dorsal pancreatic duct forms the upper part of the head, body and tail of the pancreas and drains through the duct of Santorini. The ventral bud gives rise to the major part of the head and uncinate process which drains through the duct of Wirsung [1].

Complete agenesis of pancreas and agenesis of ventral pancreas are not compatible with life. Dorsal pancreatic agenesis can be of two types, partial or complete. In partial agenesis the minor papilla is present with a remnant of the accessory pancreatic duct with variable degree of agenesis of the dorsal pancreas. In compete agenesis there is no minor papilla, accessory pancreatic duct and the complete absence of neck, body and tail of pancreas [2].

The clinical presentation can range from complete absence of symptoms to non specific abdominal pain, diabetes mellitus, pancreatitis and sometimes exocrine insufficiency. The most common clinical presentation is epigastric pain and has been assumed to be due to pancreatitis, sphincter of Oddi dysfunction or autonomic neuropathy. The reported associated anomalies include polysplenia, replaced hepatic artery and bicornuate uterus [3].

The ultrasound examination has limited role due to pancreatic bed obscured by the air in small intestine and stomach. The CT and Magnetic Resonance Imaging are useful modalities with the diagnosis of agenesis of the dorsal pancreas confirmed by demonstration of the absence of dorsal pancreatic duct either with Magnetic resonance cholangiopancreatography or endoscopic retrograde pancreatography. Imaging modalities(CT and MRI) show absent dorsal pancreas, with pancreatic bed anterior to splenic vein filled with stomach and bowel loops described as dependent stomach and dependent intestine sign respectively on CT. Discrete lobulation of head of pancreas have been described in these patients and classified into 3 types, according to their relation to the gastroduodenal artery or anterior superior pancreaticoduodenal artery [2,4].

To conclude the diagnosis of the dorsal agenesis of the pancreas is inconclusive without the demonstration of the dorsal duct and should be differentiated from pseudoagenesis  and distal pancreatic lipomatosis.