Diagnosis

Evidence suggests that, in most cases, the diagnosis of ZES is not immediately considered. In most series, there is a mean period of 6 years from presentation of symptoms to diagnosis.2 In general, ZES can be accurately diagnosed in all patients by measurement of an elevated fasting serum level of gastrin in association with an increase in basal acid output (BAO). The diagnosis can be confirmed by addition of a provocative secretin stimulation test. Measurement of the fasting serum level of gastrin is the initial study to diagnose ZES. Patients should be off antisecretory medications for 3 to 7 days prior to the determination because histamine2 (H2) blockers or omeprazole cause an artificial elevation of serum gastrin levels. All patients with ZES will have a fasting serum gastrin level of > 100 pg/mL. Fasting serum gastrin levels in individuals with renal failure, pernicious anemia, or atrophic gastritis may sometimes exceed 1,000 pg/mL; therefore, concomitant measurement of BAO is necessary to confirm the diagnosis of ZES. In this case, a BAO of >15 mEq/hour in most patients and > 5 mEq/hour in patients with prior operations to decrease gastric acid secretion unequivocally confirms the diagnosis. Confirmatory provocative testing may also be necessary to confirm the diagnosis. An increase of 200 pg/mL in the gastrin level, following secretin administration, is consistent with a diagnosis of ZES (Figure 14-15). This test has a sensitivity of 85% or greater17 and may be of particular utility in patients who have undergone prior operations to reduce acid output because these patients may have a minimally or moderately elevated gastrin level and BAO.

Figure 14-12. Intraoperative ultrasonographic image of a pancreatic gastrinoma (white arrows) approximating the common bile duct (BD). Optimally, tumors should be imaged in at least two cross-sections to clearly identify it as a mass lesion.

essary. With the introduction of H2 receptor antagonists and proton pump inhibitors (PPIs), all patients can experience control of acid hypersecretion and

Figure 14-12. Intraoperative ultrasonographic image of a pancreatic gastrinoma (white arrows) approximating the common bile duct (BD). Optimally, tumors should be imaged in at least two cross-sections to clearly identify it as a mass lesion.

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