What are the common diseases causing hematemesis and melena?

Common diseases causing hematemesis (vomiting blood) and hematochezia (blood in stool) mainly include: 1. Common causes of hematemesis: - Peptic ulcer: Ulceration of the gastrointestinal mucosa caused by gastric acid or pepsin. Hematemesis may occur when there is significant bleeding. - Cirrhosis of the liver: Hematemesis due to rupture of esophageal or gastric varices caused by excessive portal venous pressure. - Gastric cancer: Hematemesis resulting from cancer cells eroding gastric wall blood vessels and causing vessel rupture. 2. Common causes of hematochezia: - Hemorrhoids: Excessive straining during defecation leads to rupture and bleeding of hemorrhoidal nodules. - Anal fissure: Tears in the anal skin caused by hard stools and constipation, resulting in bleeding during bowel movements. - Colorectal polyps: Abnormal overgrowth of intestinal tissue, with bleeding occurring after polyps are irritated.