Why do hematemesis and melena occur when hepatic portal venous return is obstructed?

When portal venous return is obstructed, because there are no venous valves in the hepatic portal vein and its tributaries, blood can flow retrograde through anastomotic channels into the superior and inferior vena cava. In such cases, these anastomotic channels become dilated, leading to varicosities in the esophageal venous plexus and rectal venous plexus. If these enlarged veins rupture, it may result in hematemesis or melena.

Obstruction of portal venous return can cause splenic congestion and enlargement. Under normal conditions, the splenic vein from the spleen drains into the portal vein, which subsequently flows into the hepatic vein. Obstructive factors during the drainage of the portal vein into the hepatic vein—such as portal vein thrombosis, liver cirrhosis, or Budd-Chiari syndrome—can lead to increased portal pressure, resulting in splenic vein dilation and increased splenic blood flow, thereby causing splenic congestion.

Symptoms of impaired portal venous return include chest tightness, shortness of breath, and pain. The portal vein collects blood from visceral organs of the digestive system and returns it to the liver for filtration. Increased portal pressure leads to portal vein dilation, resulting in impaired venous and lymphatic return.

Patients should promptly visit a hospital for examination and treatment to identify the underlying cause and receive appropriate therapy. Treatment of the primary disease is also essential. For hepatitis B patients, entecavir or tenofovir can be administered orally; for hepatitis C and cirrhosis, antiviral therapy with sofosbuvir and velpatasvir is recommended; for Budd-Chiari syndrome, interventional therapy may be used. During treatment, patients should maintain a light diet, avoid spicy and irritating foods, and keep a relaxed mindset.