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Stomach polyps are rare, occurring in less than 1 percent of people undergoing upper gastrointestinal endoscopy — a procedure in which the lining of the stomach is examined. Stomach polyps usually don't cause symptoms. As a result, doctors often discover stomach polyps only while they're examining you for other reasons.

The three most common types of stomach polyps are:

• Hyperplastic stomach polyps. Hyperplastic stomach polyps account for more than half of all diagnosed stomach polyps. Hyperplastic polyps are usually less than a centimeter in size, but may grow much larger. These polyps develop into cancer in less than 3 percent of cases. The risk of cancer is highest in polyps greater than 2 centimeters in size. Hyperplastic polyps are associated with a condition called gastritis, which is inflammation of the stomach lining.
• Fundic gland stomach polyps. Doctors recognize that these polyps, found in the top portion of the stomach (fundus), are more common than once thought. They were previously often misidentified or simply overlooked. Fundic gland stomach polyps are less of a concern because they don't turn into cancer, except rarely in people with familial adenomatous polyposis (FAP) syndrome. Fundic gland polyps have also been associated with long-term use of the drug omeprazole (Prilosec) — which is used to treat ulcers, gastroesophageal reflux disease (GERD) and infections of Helicobacter pylori (H. pylori) bacteria in the stomach.
• Adenomas. These growths arise from the stomach's glandular tissue and account for only about 10 percent of stomach polyps, but they present a greatest health concern. These polyps can become cancerous, especially when they grow larger than 2 centimeters. These polyps are also more common in people with stomach inflammation (gastritis). Adenomas need to be removed. Removal is usually done by endoscopy, although surgery is sometimes necessary.

Small polyps usually don't cause any symptoms. However, as stomach polyps grow larger, ulcers may develop on their surface, or, rarely, the polyp may block the opening between your stomach and your small intestine.

Complications of stomach polyps may include:

• Abdominal pain, or tenderness when you press your abdomen
• Bleeding
• Nausea and vomiting
• A sense of fullness too quickly while you're eating

Signs and symptoms of inflammation of the stomach (gastritis), which may contribute to hyperplastic polyps and adenomas, also include abdominal pain, as well as belching, bloating, nausea and bleeding signaled by blood in the vomit or black stools.

People with familial adenomatous polyposis, which is associated with fundic gland polyps, may also develop hundreds of colorectal polyps at a young age. Signs and symptoms of colorectal polyps include bleeding and fatigue.

Experts aren't sure why fundic gland polyps develop. However, several problems can cause the gastritis that contributes to hyperplastic polyps and adenomas.

The most common cause of chronic gastritis is infection by H. pylori bacteria, which can also cause ulcers. About 35 percent of American adults carry these bacteria in their stomachs. Although H. pylori doesn't always cause problems, it can infect and inflame the stomach lining. The resulting damage can set the stage for polyps. One study found H. pylori in 45 percent of people diagnosed with hyperplastic polyps.

Another cause of chronic gastritis is an autoimmune reaction, in which your body forms antibodies that attack cells in the stomach and a protein needed for absorbing vitamin B-12. This process may cause vitamin B-12 deficiency anemia in many people with stomach polyps. Anemia is a condition in which you don't have enough healthy red blood cells to carry adequate oxygen to your tissues.

Factors that increase your chances of developing stomach polyps are:

• Age. Most people with hyperplastic polyps and adenomas are in their 60s or older.
• H. pylori infection. This is a common cause of the gastritis that contributes to hyperplastic polyps and adenomas. Experts aren't sure how people become infected with these bacteria, but H. pylori may be carried in food and water. H. pylori infection is also more common in older people.
• Familial adenomatous polyposis. This condition is hereditary and is caused by genetic mutations that occur in about one in 30,000 people.
• Medication use. Long-term use of proton pump inhibitors (PPIs) such as omeprazole (Prilosec) — which is used to treat ulcers, gastroesophageal reflux disease (GERD) and H. pylori infection — has been linked to fundic gland polyps.

If you have any signs or symptoms of problems that could indicate stomach polyps or the conditions leading up to them, including bleeding or persistent pain or discomfort, talk to your doctor.

If you have a stomach polyp, odds are good that your doctor detected it while looking at your stomach to seek out other problems — not necessarily polyps — that may have been causing symptoms. Imaging procedures — such as X-ray and computerized tomography — are used to diagnose polyps. More commonly, polyps are found by an upper gastrointestinal endoscopy.

An upper gastrointestinal endoscopy is a procedure in which a flexible, lighted tube is used to allow your doctor to view your esophagus, stomach, and the first part of your small intestine. The device also inflates your stomach with air, allowing the doctor to look at the stomach's folds. This procedure will reveal growths, red spots, bleeding and inflammation in the stomach.

You should avoid eating or drinking for at least six hours before endoscopy. Before putting the endoscope down your esophagus, your doctor will spray your throat with a numbing medicine or give you a sedative to relax you. The procedure should take 20 to 30 minutes, and shouldn't cause more than mild discomfort.

If your doctor finds polyps during the endoscopy, he or she may take samples (biopsy) or remove the entire growth, using special tools inserted through the endoscope. These include a small cutting device or a wire loop that burns tissue then snares it. A doctor can determine which type of polyp you have by examining its cells under a microscope.

Possible side effects from endoscopy include bleeding from the biopsy site, a sore throat, and bloating, which results from the air put into your stomach.

Depending on the type of polyp you have, your doctor may recommend a follow-up endoscopy in a year or two to see if more polyps have developed.

The most common treatment for polyps is to remove them endoscopically. When undergoing an endoscopy, polyps found are automtically removed and biopsied.

If you have gastritis caused by H. pylori bacteria in your stomach, eradicating the bacteria with antibiotics can reduce the likelihood that your polyps will return. Your doctor can determine whether you have H. pylori through a blood test. Another test requires you to drink a special liquid, then a machine analyzes your breath for signs that the bacteria are present in your stomach.

Your doctor will prescribe antibiotics — probably more than one type — for you to take for several weeks to kill the H. pylori bacteria.