Benign Diseases

On EUS, the normal pancreas has a homogeneous, fine, granular, echogenic pattern and a smooth border (see Fig 7). The pancreatic duct is smooth and less than 2 mm in diameter. The ventral pancreas tends to be less echogenic than the dorsal pancreas in many patients. Compared with EUS, a successful ERCP will provide superior imaging of the common bile duct and pancreatic duct. However, even when ERCP does not visualize a part of the pancreatic duct or common bile duct, this area will usually be seen well on EUS.

EUS can detect chronic pancreatitis in patients in whom other tests have not shown diagnostic findings. EUS findings in chronic pancreatitis have been reported [97,99]. These studies describe many duct and parenchymal findings such as increased duct size, duct irregularity, increased duct wall echogenicity, side branch visualization or dilation, strictures with dilation of the main pancreatic duct, intraluminal echoes due to calculi and protein plugs, and disruption of the duct with cyst formation. Parenchymal changes include enlargement of the gland, focal areas of reduced echogenicity, strongly echogenic foci, accentuation of lobular architecture, and cavities. Although these changes might not be picked up when EUS is used prospectively [15, 100], Lees [ 101] concluded that some of these EUS findings are characteristic only of chronic pancreatitis. If other imaging techniques fail to provide a diagnosis, EUS may add the critical information to diagnose chronic pancreatitis. When chronic pancreatitis has been diagnosed by other methods, however, EUS is currently unable to reliably differentiate focal chronic pancreatitis from carcinomas. Although EUS is at times very helpful, this is still a diagnostic problem that requires several imaging tests and even laparotomy. In known calcific pancreatitis, shadowing makes EUS image interpretation complex.

EUS can assist in diagnosis and management of pancreatitis by differentiating pancreas divisum from a cut- off, or by documenting a small cyst that is not apparent on other imaging studies. EUS has also been used to improve the safety of endoscopic drainage of pseudocyst through the gastric wall [102]. Studies on benign tumors, strictures, and anomalous connections of the biliary sys tent are limited [21].

As mentioned previously, EUS is very accurate in detecting common bile duct stones; however, ERCP is as accurate. Because stones can be removed easily after endoscopic sphincterotomy, EUS will have a limited role in detecting common bile duct stones unless ERCP is contraindicated.

Currently, EUS has no role in diagnosis of acute pancreatitis. In relapsing pancreatitis, EUS may find a cause such as a small tumor, stone, or anomaly, that was no evident on other imaging studies.

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