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PubMed This is a summary of 19 peer-reviewed journal articles Updated
Gastroenterology · Zollinger-Ellison Syndrome

Beyond Heartburn: Recognizing the Symptoms of ZES

At a Glance

Zollinger-Ellison syndrome occurs when a gastrinoma continuously releases gastrin, causing excessive stomach acid. Hard-to-heal ulcers, chronic watery or oily diarrhea, and weight loss are warning signs, and PPI changes must be supervised to avoid dangerous acid rebound.

Because its symptoms—heartburn, stomach pain, and diarrhea—are so common, Zollinger-Ellison Syndrome (ZES) is frequently mistaken for everyday digestive issues [1]. However, the underlying cause is unique: a tumor (gastrinoma) that floods your system with gastrin, a hormone that tells your stomach to produce massive amounts of acid [2]. This profound acid environment doesn’t just cause pain; it physically changes how your body digests food.

Why the Symptoms Occur: Excess Stomach Acid

In a healthy body, gastrin is released in small amounts to help digest a meal. In ZES, the gastrinoma pumps out gastrin constantly, leading to hyperchlorhydria (profoundly high stomach acid) [1].

This excess acid causes three main problems:

  • Severe Ulcers: The acid injures the protective lining of the stomach and small intestine. Unlike standard ulcers, ZES ulcers are often refractory (meaning they don’t heal after 8–12 weeks of normal treatment) and may appear in unusual places like the distal duodenum or the jejunum (deeper parts of the small intestine) [3][4].
  • Chronic Diarrhea: The sheer volume of acid and fluid entering the intestines overwhelms their ability to absorb water, leading to watery stools [5].
  • Malabsorption and Steatorrhea: High acid levels lower the pH in your small intestine so much that it inactivates pancreatic lipase—the enzyme your body needs to break down fat [6]. This causes steatorrhea (oily, foul-smelling stools that float) and can lead to unintended weight loss because your body isn’t getting the nutrients it needs [7][8].

Look-Alike Conditions

Because ZES is rare, doctors often first look for more common “look-alike” conditions. Distinguishing ZES from these requires specialized testing:

Condition How it looks like ZES How it is different
Typical GERD Causes severe heartburn and acid reflux [1]. Does not usually cause inappropriate acid hypersecretion. Note: taking PPIs for GERD can elevate gastrin, making tests confusing [9].
H. pylori Ulcers Causes stomach ulcers and pain [10]. These ulcers typically heal once the bacteria are treated with antibiotics [4].
IBS (Irritable Bowel Syndrome) Causes chronic diarrhea and abdominal pain [11]. IBS does not cause physical ulcers, GI bleeding, or malabsorption/steatorrhea [11][12].
Atrophic Gastritis Can cause very high gastrin levels in the blood [13]. This is the opposite of ZES: the body makes gastrin because there is not enough acid, rather than too much [14].
VIPoma Causes severe, watery diarrhea [15]. This tumor secretes “Vasoactive Intestinal Peptide” (VIP) instead of gastrin and does not typically cause ulcers [15].

The “PPI Mask”: Why Diagnosis Takes So Long

Proton pump inhibitors (PPIs) like omeprazole are the standard treatment for reflux. Because they are so effective at blocking acid, they often suppress ZES symptoms for years [16]. A patient might feel much better on a PPI, leading the doctor to believe they simply have bad reflux [9]. It is important to note that PPIs do not cause the tumor to grow, but they do create a “catch-22” for diagnosis:

  1. They skew test results: Taking a PPI naturally raises your gastrin levels because the body is trying to compensate for the lack of acid. This makes it hard to tell if high gastrin is from the medication or a tumor [13][17].
  2. Stopping them must be supervised: If a person with ZES stops their PPI abruptly for a test, they can experience a massive “rebound” of acid that leads to emergency complications like a perforated ulcer [1][18].

Patient Safety Rule: Never stop or change a PPI independently. Diagnostic testing for ZES must be carefully supervised by a specialist who can “bridge” your medications or perform specialized tests like a secretin stimulation test while managing your treatment safely [19][17].

Common questions in this guide

What symptoms make Zollinger-Ellison syndrome different from ordinary heartburn?
Zollinger-Ellison syndrome is more concerning when ulcers are severe, recur, fail to heal after 8 to 12 weeks of usual treatment, or occur in unusual parts of the small intestine. Chronic watery diarrhea, oily floating stools, poor nutrient absorption, and unintentional weight loss can also point beyond routine reflux.
How does a gastrinoma cause diarrhea and oily stools?
A gastrinoma releases gastrin continuously, which makes the stomach produce very large amounts of acid. The acid can overwhelm water absorption in the intestine and inactivate pancreatic lipase, an enzyme that digests fat, leading to watery diarrhea and oily, floating stools.
Can a PPI hide Zollinger-Ellison syndrome?
Yes. PPIs such as omeprazole can suppress acid and make symptoms improve, while also raising blood gastrin levels and making results harder to interpret. PPIs do not make the tumor grow, but stopping one suddenly can cause a dangerous acid rebound, so never change it without clinician guidance.
What tests are used to diagnose Zollinger-Ellison syndrome?
Clinicians may measure fasting gastrin and stomach acidity, often called gastric pH, and may use a secretin stimulation test. Because PPIs and conditions such as atrophic gastritis can also raise gastrin, results should be interpreted by a specialist with medication changes managed safely.
Why do ulcers in the jejunum or lower duodenum raise concern for ZES?
ZES ulcers may occur beyond the usual stomach or first part of the duodenum, including the distal duodenum or jejunum, and may not heal with standard treatment. An unusual location or multiple hard-to-heal ulcers is a reason to ask whether excess gastrin and acid are involved.
Could my oily, floating diarrhea be caused by a gastrinoma?
It can be. Excess acid from ZES can inactivate pancreatic lipase, so fat is not digested properly and may appear as oily, foul-smelling, floating stool; this is called steatorrhea. A clinician can decide whether stool-fat or other testing is appropriate and evaluate other causes.
What other conditions can look like Zollinger-Ellison syndrome?
GERD, H. pylori ulcers, IBS, atrophic gastritis, and VIPoma can cause some similar symptoms or test results. They differ in important ways: H. pylori ulcers may heal after antibiotic treatment, IBS does not cause ulcers or poor fat absorption, and atrophic gastritis causes high gastrin because acid is low rather than high. A clinician may need targeted testing to distinguish them.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Since my ulcers didn't heal after 8 to 12 weeks of treatment, what specific tests (like gastrin or gastric pH) should we do next?
  2. 2.Are my ulcers located in the 'typical' spot, or are they further down in the duodenum or jejunum?
  3. 3.How can we safely test my gastrin levels without causing a dangerous 'rebound' of acid if I stop my PPI?
  4. 4.Could my chronic diarrhea be caused by the acid inactivating my digestive enzymes, and should we test for fat in my stool (steatorrhea)?
  5. 5.If my gastrin is high, how do we rule out other causes like H. pylori, kidney issues, or 'atrophic gastritis'?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

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This page is for informational purposes only and does not constitute medical advice. Do not stop or change a proton pump inhibitor on your own; suspected Zollinger-Ellison syndrome requires supervised evaluation to avoid dangerous acid rebound.

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