Gastritis can be classified in several ways:
No classification scheme matches perfectly with the pathophysiology; a large degree of overlap exists. Some forms of gastritis involve acid peptic disease and H. pylori disease (see also Overview of Acid Secretion). Additionally, the term is often loosely applied to nonspecific (and often undiagnosed) abdominal discomfort and gastroenteritis.
Acute gastritis is characterized by polymorphonuclear leukocyte infiltration of the mucosa of the antrum and body.
Chronic gastritis implies some degree of atrophy (with loss of function of the mucosa) or metaplasia. It predominantly involves the antrum (with subsequent loss of G cells and decreased gastrin secretion) or the corpus (with loss of oxyntic glands, leading to reduced acid, pepsin, and intrinsic factor).