The most accurate diagnostic test for Zollinger-Ellison syndrome (ZES) is:a. Fasting serum gastrin
All patients with gastrinoma have an elevated gastrin level, and hypergastrinemia in the presence of elevated basal acid output (BAO) strongly suggests gastrinoma. Patients with gastrinoma usually have a BAO >15 mEq/h or >5 mEq/h if they have had a previous procedure for peptic ulcer. Acid secretory medications should be held for several days before gastrin measurement, because acid suppression may falsely elevate gastrin levels. Causes of hypergastrinemia can be divided into those associated with hyperacidity and those associated with hypoacidity (Fig. below). The diagnosis of ZollingerEllison syndrome (ZES) is confirmed by the secretin stimulation test. An intravenous (IV) bolus of secretin (2 U/kg) is given and gastrin levels are checked before and after injection. An increase in serum gastrin of 200 pg/mL or greater suggests the presence of gastrinoma. Patients with gastrinoma should have serum calcium and parathyroid hormone levels determined to rule out multiple endocrine neoplasia type 1 (MENl) and, if present, parathyroidectomy should be considered before resection of gastrinoma.
Algorithm for diagnosis and management of hypergastrinemia:
B 1 = Billroth I; B 2 = Billroth II; BAO = basal acid output; Bx = biopsy; ECL = enterochromaffin-like; EGO = esophagogastroduodenoscopy; GJ = gastrojejunostomy; H2RA = histamine 2 receptor antagonist; insuff = insufficiency; MEN 1 = multiple endocrine neoplasia type 1; PPI = proton pump inhibitor; R/0 = rule out; SB = small bowel; S/P = status post; TV = truncal vagotomy; TV and A= truncal vagotomy and antrectomy.