Diagnosis of Zollinger-Ellison Syndrome

Initial Diagnostic Approach

The American Gastroenterological Association recommends measuring fasting serum gastrin after discontinuing proton pump inhibitors for 1-2 weeks to avoid false elevations 1

Vasoactive intestinal peptide is used to diagnose VIPomas, not gastrinomas, which cause watery diarrhea-hypokalemia-achlorhydria syndrome, a different functional pancreatic neuroendocrine tumor 2
Renal failure is a common cause of hypergastrinemia that must be ruled out before pursuing ZES diagnosis 1

ZES should be suspected in patients presenting with severe peptic ulceration refractory to standard therapy 1
ZES should be suspected in patients presenting with chronic diarrhea, which occurs in approximately 50% at diagnosis 1
ZES should be suspected in patients presenting with gastroesophageal reflux disease refractory to standard therapy 1
ZES should be suspected in patients presenting with epigastric pain lasting years despite acid-suppressive therapy, reported in 70% at diagnosis 1