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A gastrinoma is a tumor usually in the pancreas or duodenum (the first segment of the small intestine) that produces excessive levels of the hormone gastrin, which stimulates the stomach to secrete acid and enzymes, causing peptic ulcers.
Gastrinomas are a type of pancreatic endocrine tumor. Most people with gastrinomas have several tumors clustered in or near the pancreas or the duodenum. About half of the tumors are cancerous. Sometimes a gastrinoma occurs as part of multiple endocrine neoplasia, a hereditary disorder in which tumors arise from the cells of various endocrine glands, such as the insulin -producing cells of the pancreas.
The excess gastrin secreted by the gastrinoma causes Zollinger-Ellison syndrome , in which a person suffers the symptoms of aggressive peptic ulcers in the stomach, duodenum, and elsewhere in the intestine. However, as many as 25% of people with Zollinger-Ellison syndrome may not have an ulcer when the diagnosis is made. Rupture, bleeding, and obstruction of the intestine can occur and are life threatening. For more than half of the people with a gastrinoma, symptoms are no worse than those experienced by people with ordinary peptic ulcer disease. In 25 to 40% of people, diarrhea is the first symptom.
A doctor suspects a gastrinoma when a person has frequent peptic ulcers or several peptic ulcers that do not respond to the usual ulcer treatments. Blood tests to detect abnormally high levels of gastrin are the most reliable diagnostic tests.
Once blood tests diagnose gastrinoma, doctors use several imaging techniques, such as computed tomography (CT) of the abdomen, scintigraphy (a type of radionuclide scanning), endoscopic ultrasonography, positron emission tomography (PET) scans, and arteriography (an x-ray taken after a radiopaque dye is injected into an artery), to locate tumors. These tumors may be difficult to find, however, because usually they are small.
High doses of proton pump inhibitors (see Acid-reducing drugs and see Table: Drugs Used to Treat Peptic Ulcer Disease) may be effective for reducing acid levels and relieving symptoms temporarily. If these drugs are not effective enough, injections of octreotide may help. If there is only one tumor and the person does not have multiple endocrine neoplasia, doctors usually do surgery to remove the gastrinoma. In such cases, surgical removal cures about 20% of people.
If these treatments do not work, an operation to remove the stomach completely (total gastrectomy) may be necessary. This operation does not remove the tumor, but the gastrin can no longer create ulcers after the acid-producing stomach is removed. If the stomach is removed, daily iron and calcium supplements taken by mouth and monthly injections of vitamin B12 are needed, because absorption of these nutrients is impaired when stomach juices that prepare these nutrients for absorption are no longer available.
If cancerous tumors have spread to other parts of the body, chemotherapy may help reduce the number of tumor cells and the levels of gastrin in the blood. However, such therapy does not cure the cancer, which is ultimately fatal.
In Zollinger-Ellison syndrome, the stomach produces far too much acid, which causes people to develop many peptic ulcers. In this syndrome, the excess acid is produced because a tumor called a gastrinoma produces gastrin. Gastrin is a hormone that stimulates the stomach to produce acid.
The gastrinoma tumor is usually found in the duodenum, pancreas, or adjacent structures. About half of the tumors are cancerous (malignant). People with Zollinger-Ellison syndrome frequently develop many peptic ulcers that recur despite treatment to control ulcer disease. They may also develop diarrhea that is difficult to control and/or symptoms of acid reflux ( gastroesophageal reflux or GERD).
People with this disease typically have an elevated level of gastrin in their blood, which can be measured to make the diagnosis.
Sometimes, testing involves giving the person a hormone called secretin. In people with Zollinger-Ellison syndrome, gastrin levels in the bloodstream greatly increase when secretin is injected into a vein. In addition, testing can reveal increased production of stomach acid.
A number of tests can be done in an attempt to find the tumor's location, including computed tomography (CT) scanning, endoscopic ultrasonography, arteriography (an x-ray taken after a radiopaque dye is injected into an artery), and radionuclide scanning.
Other tests are done to look for Helicobacter pylori infection.
Proton pump inhibitors help control the excess production of stomach acid. People who are not helped by proton pump inhibitors may be given injections of octreotide.
Surgery to remove the tumor can be curative. Even when not curative, surgery can reduce the tumor size, which in turn reduces the amount of acid produced by the stomach and prevents local complications, such as blockage of the intestine.
Chemotherapy may be helpful in people whose cancer has spread. Although chemotherapy may reduce tumor size and levels of gastrin in the blood, it is not curative.
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