EUS has clearly emerged as the most accurate test for imaging pancreatic disease. Techniques to image the pancreas have been described [20]. If the entire pancreas and other retroperitoneal structures are to be visualized, the echoendoscope must be inserted to the horizontal duodenum. Frequently, to achieve optimal scanning of the pancreas and the surrounding vessels, the transducer must be anchored in the duodenal bulb by inflating the balloon surrounding the transducer with water. Then, by withdrawing the scope, the pylorus will be pulled back and the lesser curve of the stomach shortened. This "withdrawn wedged" position improves control of the angle of scanning of the pancreas [20] (Figs 7,8,9).

Conventional initial evaluation of a patient with a suspected pancreatic carcinoma usually consists of transcutaneous US, CT scan, or both. A direct relationship exists between mass size and the sensitivity and specificity of these tests for detection, staging, and assessment of resectability. For patients with small lesions, for whom resection is generally considered to be the best palliation and may offer the best chance of improved survival, preoperative evaluation is most difficult.

EUS can identify localized pancreatic, biliary, or peri- ampullary neoplasm and differentiate it from disease with regional lymph nodes, metastatic spread, or, most importantly, extrapancreatic extension into blood vessels [79,80]. The retrospective study by Yasuda and col leagues [81] reports on the detection rate of pancreatic tumors by EUS, CT scans, standard US, angiography, and ERCP. An important aspect of the study concerns the size of the tumor. For lesions that were larger than 3 cm, all tests were quite good at detecting tumors: EUS detected 100%; the other tests detected 82 to 97%. How ever, for tumors that were less than 3 cm, the difference in detection rate between EUS and other tests increases dramatically: 100% compared with 24, 57, 29, and 14%, respectively.

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