Helicobacter Pylori Infection, Causes, Signs and Symptoms, Diagnosis and Treatment.

Helicobacter pylori, previously known as Campylobacter pylori, is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach.[5] Its helical shape (from which the genus name, helicobacter, derives) is thought to have evolved in order to penetrate the mucoid lining of the stomach and thereby establish infection.[7][8] The bacterium was first identified in 1982 by Australian doctors Barry Marshall and Robin Warren.[9][10][11] H. pylori has been associated with lymphomas of the mucosa-associated lymphoid tissue in the stomach, esophagus, colon, rectum, or tissues around the eye (termed extranodal marginal zone B-cell lymphoma of the cited organ),[12][13] and of lymphoid tissue in the stomach (termed diffuse large B-cell lymphoma).[14]

H. pylori infection usually has no symptoms but sometimes causes gastritis (stomach inflammation) or ulcers of the stomach or first part of the small intestine. The infection is also associated with the development of certain cancers occurring in less than 20% of cases.[15] Many investigators have suggested that H. pylori causes or prevents a wide range of other diseases, but many of these relationships remain controversial.[16][17][18][19]

Some studies suggest that H. pylori plays an important role in the natural stomach ecology, e.g. by influencing the type of bacteria that colonize the gastrointestinal tract.[15][18] Other studies suggest that non-pathogenic strains of H. pylori may beneficially normalize stomach acid secretion,[20] and regulate appetite.[20]

In 2015, it was estimated that over 50% of the world's population had H. pylori in their upper gastrointestinal tracts[6] with this infection (or colonization) being more common in developing countries.[4] In recent decades, however, the prevalence of H. pylori colonization of the gastrointestinal tract has declined in many countries.[21] Up to 90% of people infected with H. pylori never experience symptoms or complications.[22] However, individuals infected with H. pylori have a 10% to 20% lifetime risk of developing peptic ulcers.[23][24] Acute infection may appear as an acute gastritis with abdominal pain (stomach ache) or nausea.[3] Where this develops into chronic gastritis, the symptoms, if present, are often those of non-ulcer dyspepsia: Stomach pains, nausea, bloating, belching, and sometimes vomiting.[25][26] Pain typically occurs when the stomach is empty, between meals, and in the early morning hours, but it can also occur at other times. Less common ulcer symptoms include nausea, vomiting, and loss of appetite.

Bleeding in the stomach can also occur as evidenced by the passage of black stools; prolonged bleeding may cause anemia leading to weakness and fatigue. If bleeding is heavy, hematemesis, hematochezia, or melena may occur. Inflammation of the pyloric antrum, which connects the stomach to the duodenum, is more likely to lead to duodenal ulcers, while inflammation of the corpus (i.e. body of the stomach) is more likely to lead to gastric ulcers.[27][28] Individuals infected with H. pylori may also develop colorectal[29][30] or gastric[31] polyps, i.e. non-cancerous growths of tissue projecting from the mucous membranes of these organs. Usually, these polyps are asymptomatic but gastric polyps may be the cause of dyspepsia, heartburn, bleeding from the upper gastrointestinal tract, and, rarely, gastric outlet obstruction[31] while colorectal polyps may be the cause of rectal bleeding, anemia, constipation, diarrhea, weight loss, and abdominal pain.[32]

Individuals with chronic H. pylori infection have an increased risk of acquiring a cancer that is directly related to this infection.[12][13][23][24] These cancers are stomach adenocarcinoma, less commonly diffuse large B-cell lymphoma of the stomach,[14] or extranodal marginal zone B-cell lymphomas of the stomach,[33][34] or, more rarely, of the colon,[13][34] rectum,[35] esophagus,[36] or ocular adenexa (i.e. orbit, conjunctiva, and/or eyelids).[37][38] The signs, symptoms, pathophysiology, and diagnoses of these cancers are given in the cited linkages.