Zollinger-Ellison Syndrome Workup

Updated: Jan 04, 2019
  • Author: Praveen K Roy, MD, MSc; Chief Editor: Philip O Katz, MD, FACP, FACG  more...
  • Print

Laboratory Studies

Diagnostic laboratory studies include measurement of gastric pH and levels of fasting gastrin and chromogranin A, as well as secretin stimulation. [1, 3]

Fasting serum gastrin levels

Fasting serum gastrin is the best single screening test for Zollinger-Ellison syndrome (ZES). Preferably, patients should not be taking gastric antisecretory medications at the time of the test, but this is not essential for the initial screen.

Because fasting gastrin levels can fluctuate from day to day and can appear to be normal, serial measurements on different days should be performed.

Normal levels of serum gastrin in untreated ZES are extremely rare (< 1%).

Serum calcium levels

Elevated serum calcium levels should prompt a search for multiple endocrine neoplasia-type 1 (MEN 1) syndrome.

Gastric acid secretory tests

Basal acid output (BAO) greater than 15 mEq/h or greater than 5 mEq/h in patients with a prior vagotomy and partial gastrectomy is suggestive of ZES.

Basal gastric secretory volume greater than 140 mL in patients with no prior gastric acid–reducing surgery has a high sensitivity and specificity.

Gastric pH less than 2.0 in the presence of a large gastric volume (>140 mL over 1 h in patients without prior gastric acid–reducing surgery) is highly suggestive of ZES.

Currently, maximal acid output measurement is rarely performed.

Provocative tests

Various provocative diagnostic tests for ZES have been proposed, including the secretin stimulation test, calcium stimulation test, secretin-plus-calcium stimulation tests, bombesin test, and protein meal test.

The secretin stimulation test is the provocative test of choice because of its higher sensitivity. In this test, a 2-U/kg bolus of secretin is administered intravenously after an overnight fast, and serum levels of gastrin are determined at 0, 2, 5, 10, and 15 minutes. An increase in serum gastrin of greater than 200 pg/mL is diagnostic.

Potential algorithm for suspected gastrinoma

A suggested algorithm for the evaluation of a patient with suspected gastrinoma is as follows:

  • Step 1: Check the fasting gastrin level. Measure at least 3 fasting levels of gastrin on different days.

  • Step 2: Perform gastric acid secretory studies. A BAO value of greater than 15 mEq/h or a gastric volume of greater than 140 mL and pH of less than 2.0 are highly suggestive of gastrinoma.

  • Step 3: Perform a provocative test. The secretin stimulation test is the preferred test.

  • Step 4: Perform somatostatin receptor scintigraphy (SRS).

  • Step 5: Perform imaging studies to stage and localize the gastrinoma.

  • Step 6: Determine if patient is a surgical candidate for tumor resection.


Imaging Studies

Somatostatin receptor scintigraphy

Somatostatin receptor scintigraphy (SRS) is the most sensitive imaging modality for detection of primary or metastatic lesions in Zollinger-Ellison syndrome (ZES); thus, is the imaging modality of choice in ZES.

Computed tomography scanning

Computed tomography (CT) scanning can be performed to localize the tumor and is useful for evaluation for metastatic disease. However, its sensitivity for primary tumor localization is only 50%, and frequently, tumors smaller than 1 cm are missed.

Positron-emission tomography/CT scanning in conjunction with 68gallium (68Ga)-labeled somatostatin radiotracers (ie,68Ga-DOTATOC, 68Ga-DOTANOC, 68Ga-DOTATATE) yields particularly good results. [1]

Other imaging studies

Magnetic resonance imaging (MRI) and abdominal ultrasonography also can be performed. However, the sensitivity of these modalities is lower than that of CT scanning and SRS.

Endoscopic ultrasonography is one of the relatively newer methods for localizing gastrinomas. Its sensitivity is higher for pancreatic gastrinoma (40-75%) than for duodenal gastrinoma (50%). This imaging modality may be particularly useful in those with ZES and multiple endocrine neoplasia (MEN) type 1. [1]




Esophagogastroduodenoscopy should be performed to look for duodenal ulcerations and hypertrophy of gastric folds. Sensitivity for hypertrophic gastric folds is 94%. Rarely, thickened duodenal folds also may be present.