Peptic Ulcer Disease

Many studies have demonstrated a link between H. pylori infection and gastric cancers (3-7). In 1994, the International Agency for Research on Cancer (IARC) classified H. pylori as a carcinogen, or cancer-causing agent, despite conflicting results at the time.

Since then, colonization of the stomach with H. pylori has been increasingly accepted as an important risk factor for gastric cancers. However, this association varies by region of the stomach. In 2001, a combined analysis of 12 H. pylori and gastric cancer studies estimated that the risk of non-cardia gastric cancer was nearly six times higher for H. pylori-infected people than for uninfected people (3). Data show that infection with H. pylori plays an important role in the development of non-cardia gastric cancer, but its association with gastric cardia cancer is less clear.

stric cancer, or cancer of the stomach, was once considered a single entity. Now, epidemiologists divide this cancer into two main classes: gastric cardia cancer (which is cancer of the top inch of the stomach, where it meets the esophagus) and non-cardia gastric cancer (cancer in all other areas of the stomach). This classification was adopted because these two types of stomach cancer have different risk factors and different patterns of occurrence. For example, H. pylori has been established as a strong risk factor for non-cardia gastric cancer, whereas its association with gastric cardia cancer is controversial.

Peptic ulcers are holes in the lining of the stomach or upper small intestine (duodenum) that extend deep into the muscular layers of these organs. An ulcer forms when surface cells become inflamed, die, and are shed. The damage can be caused by mechanical abrasion, infection, or inflammation, which results from an overreaction of immune cells.

Peptic ulcer disease (PUD) is responsible for over three million visits to the doctor per year in the United States. Stomach pain similar to heartburn or indigestion is the most prevalent symptom of a stomach ulcer. Other symptoms may include loss of appetite, weight loss, vomiting, blood in the stool, or anemia.

Human infection with H. pylori is common; the Centers for Disease Control and Prevention estimate that approximately two-thirds of the world's population harbors the bacterium, with infection rates much higher in developing nations than in Europe and North America.

H. pylori is thought to be spread either through contaminated food and water or through direct mouth-to-mouth contact. In most populations, the bacterium is first acquired during childhood. Children living in crowded conditions and with a lower socioeconomic status are more likely to become infected.

In the 1980s, scientists began to notice the presence of curved bacteria, which later became known as H. pylori, in tissue samples taken from patients with ulcers of the stomach and upper small intestine. Believing that no bacteria could survive the harsh stomach environment, most scientists thought these mysterious bacteria were either due to contamination of tissue samples or just another harmless species of bacteria like many found in the gut.

Helicobacter pylori, or H. pylori, is a spiral-shaped bacterium that is able to grow in the human stomach. Normally, the acidic stomach environment prevents the survival of viruses, bacteria, and other microorganisms. However, H. pylori has evolved to be uniquely suited to thrive in the harsh stomach environment. H. pylori bacteria secrete urease, a special enzyme that converts urea to ammonia. Ammonia reduces the acidity of the stomach, making it a more hospitable home for H. pylori.