Endoscopic ultrasound in the evaluation and treatment of chronic pancreatitis.

Endoscopic ultrasound (EUS) was developed in the 1970s specifically for the purpose of improved imaging of the pancreas. The close proximity of the pancreas to the gastric and duodenal lumen allows EUS to obtain high-resolution images, unobstructed by overlying bowel gas. EUS has fewer complications than endoscopic retrograde cholangiopancreatography (ERCP) and can detect features of chronic pancreatitis (CP) in the pancreatic parenchyma and duct that are not visible to any other imaging modality. Because of this high sensitivity, questions have arisen whether EUS is oversensitive, especially to ''early" CP. Without a definitive gold standard against which to measure EUS (or ERCP and function testing), it is currently not possible to know the true accuracy of these modalities for early CP. There is now an extensive body of literature suggesting that these early changes detected by EUS correlate with histologic changes of CP, and may predict response to pancreatic therapy. EUS is uniquely suited to performing endoscopic cyst drainage for pancreatic pseudocysts and for controlling the pain of CP by EUS-directed celiac plexus block. For endoscopic cystenterostomy, EUS allows the endoscopist to localize the cyst, determine if the cyst is drainable, and guide a needle and stent into the cyst in a single step. Several major questions remain. Can EUS features of CP guide other forms of therapy for CP such as enzyme replacement, sphincter of Oddi therapy, and stent therapy? Can the detection of early CP by EUS, and subsequent therapy, delay or prevent the onset of more severe CP? Can EUS detect early forms for dysplasia and malignancy in patients who are at high risk for pancreatic carcinoma? Do changes of "early" CP detected by EUS progress to more classic changes (calicification) over time?