Chapter 47 Gastritis and peptic ulcer disease
Peptic ulceration is defined as a breach in the mucosa (i.e. full-thickness loss) of the gastrointestinal tract caused by the action of acidic gastric juice. Peptic ulcers can be acute or chronic, although sometimes the term peptic ulcer is confined to the chronic variety (Fig. 3.47.1). Some types of inflammation of the stomach (gastritis) are especially associated with peptic ulcer formation, and these are discussed in this chapter.
The principal causes of acute gastritis are:
Acute gastritis is often associated with partial-thickness defects in the mucosa. Such defects are sometimes called erosions (as opposed to an ulcer, which is a full-thickness breach). These erosions often bleed and may present as gastric haemorrhage. In severe cases, the erosions deepen to become true ulcers.
Chronic gastritis can be generated by any of the causes of acute gastritis if they act for long enough. In addition, chronic gastritis can occur de novo through autoimmune mechanisms. For example, pernicious anaemia is an autoimmune condition in which damage to parietal cells causes l0ss of intrinsic factor and hence failure of vitamin B12 absorption. It is associated with inflammation and subsequent atrophy of the mucosa in the gastric body and fundus. However, the most common cause of chronic gastritis is infection with Helicobacter pylori.
Although H. pylori does not invade the tissues, it lives in the surface mucus of gastric mucosa (Fig. 3.47.2) where it secretes a number of toxins that damage surface epithelial cells and break down the mucus barrier. When first acquired, this organism produces a transient acute gastritis, but this is self-limiting and often produces no symptoms. Some individuals mount an effective defence and eliminate the organism. Many individuals do not clear the organism, however, and a chronic carrier state develops. This carrier state is associated with chronic inflammation of the mucosa driven by a Th1 immune response, the severity of the inflammation depending on the strain of the infecting organism. As a result, patients may either have abdominal symptoms or be asymptomatic. The most common serious sequela of H. pylori infection is peptic ulceration.
Fig. 3.47.2 Helicobacter pylori in the surface mucus of the stomach. Modified Giemsa stain, oil immersion lens.