Overview
In Zollinger-Ellison syndrome (ZES), a tumour called a gastrinoma produces too much of a hormone called gastrin. Gastrin tells the stomach to make acid, so the stomach produces far more acid than normal. The excess acid injures the lining of the stomach, the duodenum (first part of the small bowel) and sometimes the esophagus, leading to ulcers, reflux and diarrhea. Gastrinomas are a type of neuroendocrine tumour, usually small, and most often found in the duodenum or pancreas. Some are slow growing, but some can spread, so careful assessment is needed.
Symptoms
Burning upper belly pain, like a peptic ulcer, that may be severe and persistent
Heartburn and acid reflux
Diarrhea, sometimes fatty, caused by too much acid in the bowel
Nausea, vomiting and poor appetite
Weight loss
Bleeding from an ulcer, causing black stool or tiredness from anemia
Self-Care Tips
Never stop acid-lowering medicine suddenly; carry a list of your medicines when travelling.
Make sure all your doctors know the diagnosis.
Support from your specialist team and family helps with the worry of a rare diagnosis.
When to See a Doctor
Seek medical care promptly if you notice: Vomiting blood or black, tar-like stool; Sudden severe belly pain with a rigid belly; Repeated vomiting and inability to eat or drink; Severe or watery diarrhea with dizziness or muscle cramps; Ulcers that keep returning despite treatment, or unintended weight loss.
Why it happens
Most gastrinomas occur by chance. A minority are part of an inherited condition called multiple endocrine neoplasia type 1 (MEN1), which can affect the parathyroid glands, pituitary gland and pancreas. Your doctor may ask about your family history and check calcium levels and other hormones.
How common it is
It is rare and is often missed or diagnosed late because its symptoms look like common ulcer or reflux disease. It should be suspected when ulcers are severe, come back, or are in unusual places, or when reflux with chronic diarrhea does not settle.
How it is diagnosed
Testing begins with a blood test for fasting gastrin level. Because many common medicines (especially acid-lowering medicines called proton pump inhibitors) raise gastrin, interpretation can be difficult. Your specialist may check stomach acid levels or perform a secretin stimulation test. Upper endoscopy shows ulcers and thickened folds. Imaging such as CT, MRI, endoscopic ultrasound and specialised scans are used to find the tumour and see whether it has spread. Do not stop acid-lowering medicine before testing unless your doctor tells you to, because stopping suddenly can be dangerous.
Lifestyle and daily habits
Taking acid control seriously and staying in regular follow-up protects you from complications.
• Take acid-lowering medicine exactly as prescribed; do not skip or stop it, as a rebound of acid can cause bleeding ulcers.
• Stop smoking, which worsens ulcers.
• Avoid NSAID painkillers unless your doctor agrees.
• Attend regular tests and scans to monitor the tumour.
• Tell family members about the diagnosis if MEN1 is suspected so they can be advised about screening.
Diet
Diet does not cure the condition, but eating well helps recovery from diarrhea and weight loss.
• Eat regular balanced meals with enough protein and calories.
• Limit foods or drinks that clearly make your symptoms worse.
• Drink enough fluids, especially if you have diarrhea.
• Long-term acid suppression can lower absorption of vitamin B12, iron, calcium and magnesium; ask your doctor about monitoring.
Medicines
Medicines to control stomach acid are the backbone of treatment. Doses are often higher than usual and are set by your specialist.
• Proton pump inhibitors (PPIs) are the main medicines and usually control the acid and heal ulcers.
• Take your medicine at the times advised; your doctor may adjust it based on symptoms and tests.
• Medicines for the tumour itself (for example somatostatin-type injections or other cancer treatments) may be used if it has spread; the specialist team decides.
• Report side effects such as persistent diarrhea, bone pain or tingling.
Procedures and surgery
If the tumour can be found and is in a place where it can be removed, surgery offers a chance of cure.
• Endoscopy and endoscopic ultrasound help find and sample the tumour.
• Surgery to remove the tumour is considered when suitable, often by experienced pancreatic or endocrine surgeons.
• Other procedures may be used for tumours that have spread to the liver.
• Endoscopy may treat bleeding ulcers when they occur.
Latest science
Modern acid-suppressing medicines control symptoms and ulcers very well, so the main long-term concern is the tumour itself. Specialist teams now use advanced imaging to find small tumours and decide whether surgery can cure the disease. Treatment of tumours that have spread is individualised.
Outlook
Acid control is usually very effective, and many people live with good symptom control. The long-term outlook depends on the tumour: whether it can be removed, whether it has spread, and whether MEN1 is present. Regular follow-up is important.
Questions to ask your doctor
• How certain is the diagnosis, and what further tests do I need?
• Where is the tumour and can it be removed?
• Do I need genetic testing or screening for MEN1?
• How long will I need acid-lowering medicine?
• What follow-up and scans will I need?
Source and review
This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.
Frequently Asked Questions
What is Zollinger-Ellison Syndrome?
How is Zollinger-Ellison Syndrome diagnosed?
What is the outlook for Zollinger-Ellison Syndrome?
When should I see a doctor about Zollinger-Ellison Syndrome?
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