Zollinger–Ellison Syndrome - Diagnosis

Diagnosis

Tests used to diagnose Zollinger-Ellison syndrome are:

• Blood tests: Blood tests show a rise in gastrin levels. However, other conditions can also result in increased gastrin levels; thus the test used alone is not diagnostic of gastrinoma.
• In a normal human being, fasting gastrin levels are less than 150 pg/mL. Gastrinoma patients usually have a gastrin level more than 150-200 pg/mL. Levels of gastrin are obtained with patients not taking H2-receptor antagonists for 24 hours or proton pump inhibitors for 6 days. These are the drugs commonly prescribed for ulcer disease.
• Gastric acid measurements

  : Gastric acid measurements may be done to check for acid hypersecretion. In case this is not possible, the basal gastric pH is measured. A basal gastric pH greater than or equal to 3 excludes gastrinomas.

• Secretin test: In the secretin test, basal gastrin concentration is first measured with a blood test. Secretin is then injected into a vein and samples at regular intervals are collected for up to a duration of 30 minutes. An increase of plasma gastrin levels of over 200 pg/mL within 2-30 minutes is seen in 85% of patients with gastrinoma.
• Imaging studies: Imaging studies are required to locate the gastrinomas and evaluate their stage. An important imaging study in this context is the somatostatin receptor scintigraphy (SRS) using ¹¹¹In-pentetreotide with single photon emission tomography (SPECT) scanning. Endoscopic ultrasound, CT scan and MRI may also be used.
• Functional studies: Functional studies that measure hormone gradients by transhepatic portal venous sampling may also be used.

References:

1. Harrison�s Principles of Internal Medicine 17^th edition.
2. Tomassetti P, et al. Treatment of Zollinger-Ellison Syndrome. World J Gastroenterol 2005;11(35):5423–5432.