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Erosion = lesion superficial to muscularis mucosae
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Superficial lesions which do not penetrate the muscularis mucosae are called erosions. Acute erosive gastritis is rarely an important cause of upper gastrointestinal bleeding because the larger arterioles are deeper in the submucosa.
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Ulcer = lesion deep to muscularis mucosa
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Deeper lesions are formed when erosions enlarge and extend below the muscularis mucosa into the submucosa. These lesions may cause severe bleeding, or may perforate the gastric wall. Severely ill patients, often with multi-organ failure can be burdened further with acute gastric or duodenal ulcers whose underlying pathogenesis is ischemia of the gut wall. If the patient survives, acute ulcers usually heal. Some scarring occurs, but, in a few weeks, the site of an acute ulcer may be difficult or impossible to find.
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Etiology of acute erosive gastritis: idiopathic, NSAIDs, severe stress, infectious agents
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Gastritis can occur for no apparent cause. Some cases are associated with ingestion of anti-inflammatory drugs such as aspirin or with acute infections with Helicobacter pylori. Erosions and acute ulcers may accompany the severe stress of burns, sepsis, trauma, shock, or respiratory failure. Underlying mechanisms which lead to acute disruption of gastric mucosa are poorly understood. Perhaps the initial injury is chemical, ischemic, or bacterial. Alterations in mucosal blood flow may lead to areas of microinfarction. Further evolution after the initial injury may depend on acid-peptic digestion.
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Next Section (I): Chronic Disruptions of Gastric Mucosa »
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