Most Common Site of Zollinger-Ellison Syndrome (ZES) Gastrinoma
The majority of gastrinomas causing Zollinger-Ellison syndrome are located in the duodenum, with the remainder typically found in the pancreas. 1
Anatomical Distribution of Gastrinomas
- Gastrinomas are most commonly found within the "gastrinoma triangle," which involves parts of the duodenum, pancreas, and extra-hepatic biliary system 2
- The duodenum is the predominant site for gastrinomas, followed by the pancreas 1, 2
- In patients with Multiple Endocrine Neoplasia type 1 (MEN1), gastrinomas are also predominantly found in the duodenum 3
Diagnostic Approach for Gastrinomas
- Diagnosis begins with measurement of fasting serum gastrin levels (>100 pg/mL is suspicious, >1000 pg/mL with gastric pH <2 is diagnostic) 2
- Proton pump inhibitors should be discontinued for at least one week and H2 receptor antagonists for 48 hours before testing 2
- The secretin stimulation test helps differentiate ZES from other causes of hypergastrinemia 2, 4
- Basal acid output (BAO) measurement is useful in confirming the diagnosis 4
Imaging for Localization
- Endoscopic ultrasound has high sensitivity (up to 83%) for pancreatic gastrinomas but lower detection rates for duodenal lesions 2
- Gallium-68 radiotracers with positron emission tomography are currently the standard for tumor localization 2
- Somatostatin receptor scintigraphy is useful for initial evaluation of suspected gastrinomas 5
- CT and MRI scans should be multiphase for optimal detection 5
Management Considerations
- Proton pump inhibitors are the cornerstone of symptomatic treatment 2
- Surgery is routinely performed in localized sporadic ZES, even with negative imaging results 2, 4
- For patients with MEN1 and ZES, surgical approach is more controversial, with some advocating surgery only for tumors larger than 2 cm 4
- All patients with ZES should be evaluated for MEN1 syndrome 1
Clinical Pitfalls to Avoid
- Failure to discontinue acid-suppressing medications before diagnostic testing can lead to false-negative results 2
- Missing the diagnosis of MEN1 in ZES patients (occurs in approximately 20% of cases) 6
- Overlooking duodenal gastrinomas during surgical exploration, which are often small and can be missed without careful examination including duodenotomy 4
- Assuming gastrinomas are primarily pancreatic when they are more commonly duodenal 1, 2
Understanding the predominant duodenal location of gastrinomas is crucial for proper surgical planning and optimal outcomes in patients with Zollinger-Ellison syndrome.