[Differential sonographic diagnosis. Pancreas (pseudo) cyst--choledochus cyst].

The case of a woman patient with an extended prepapillary choledochal cyst and pancreaticobiliary reflux shows that it is necessary to consider the possibility of a choledochal cyst on detecting a cystic structure in the head of the pancreas (condition after acute pancreatitis); besides this, differential diagnosis will have to consider a pancreatic pseudocyst, hydrops of the gallbladder, a retroperitoneal cyst or even vascular aneurysm. If necessary, the physician should take suitable diagnostic measures before performing any percutaneous cyst drainage which he may have planned, since this may entail the risk of biliary peritonitis.