Diagnosis of pancreas divisum by endoscopic ultrasonography

During pancreatobiliary imaging by endoscopic ultrasound (EUS) at the authors' institution, it is customary to attempt to obtain the "stack sign", where the bile duct and the pancreatic duct can be seen to run in parallel through the pancreatic head. We suspected that such a view may not be attainable in patients with pancreas divisum because of the short ventral pancreatic duct. The aim of the study was to investigate whether the presence of pancreas divisum could be suspected on the basis of EUS findings.

The stack sign is obtained by positioning the echo endoscope in the long scope position with the transducer in the duodenal bulb. The balloon is then inflated and advanced snugly into the apex of the bulb. From this position, the bile duct (closest to the transducer) and the pancreatic duct can be seen to run in parallel through the pancreatic head. We attempted to obtain a stack sign during EUS examinations of six patients with pancreas divisum. EUS was done in these patients to look for evidence of chronic pancreatitis and the pancreas divisum was confirmed by endoscopic retrograde pancreatography. An attempt to obtain the stack sign was also made in 30 patients who had EUS for pancreatobiliary indications but did not have pancreas divisum.

In only two out of six patients with pancreas divisum (33 %) were we able to obtain a stack sign. This was significantly different from the rate of observation of a stack sign in 83.3 % (25/30) of patients who did not have pancreas divisum (P=0.04). Of the two patients with pancreas divisum in whom a stack sign was seen, the ventral duct was markedly dilated (6.6 mm) in one, and the other patient had an unusually large ventral pancreas.

The absence of a stack sign during pancreatobiliary imaging by EUS may suggest the diagnosis of pancreas divisum.