PHYSICAL EXAMINATION

LABORATORY STUDIES

DIAGNOSIS

Peptic ulcer

PATHOPHYSIOLOGY OF KEY SYMPTOMS

Acid-base balance of the stomach and small intestine results from acid secretion in the stomach (Fig. 53-1) that is neutralized by the bicarbonate secretion of the small intestine (Fig. 53-2). The gastric and duodenal mucosa is protected from damage by the luminal pH by a layer of mucus. Damage to the mucosal layer causes pain and can cause bleeding into the intestinal lumen. The presence of blood in the stool indicates that the mucosal layer has been damaged.

FIGURE 53–1 Postulated mechanism for secretion of hydrochloric acid. (The points labeled “P” indicate active pumps, and the dashed lines represent free diffusion and osmosis.)

FIGURE 53–2 Secretion of isosmotic sodium bicarbonate solution by the pancreatic ductules and ducts.