Portal Hypertension Pathophysiology

Portal hypertension is a condition that occurs when there’s abnormally high pressure in the portal venous system, which is a network of vessels that drain blood from the abdomen into the liver.

As a quick review, the portal vein is formed by the splenic vein merging with the superior and inferior mesenteric veins, so it receives blood from the spleen, stomach, pancreas, and small and large intestines.

This blood contains all the nutrients absorbed in the GI tract, as well as ingested medications and potential toxins.

The slow, low-pressure flow of blood provides adequate time for the liver to extract nutrients, metabolize medications, and remove toxins before they reach systemic circulation.

Once the liver processes the blood it receives, it flows through the hepatic veins to the inferior vena cava, and to the right atrium of the heart. The blood then flows through the heart and lungs, and oxygenated blood is pumped out to the rest of the body.

Now, portal hypertension is caused by any condition that obstructs blood flow in the portal venous system, and can be prehepatic, intrahepatic, or posthepatic.

Prehepatic causes are those that result in obstruction of blood flow before reaching the liver such as splenic vein thrombosis, or a clot within the splenic vein.

Intrahepatic causes are those which result in an obstruction within the liver. One of the most common causes is cirrhosis, a condition where healthy liver tissue is replaced by scar tissue resulting in increased resistance to blood flow through the liver.

Other causes include certain infections like hepatitis or schistosomiasis, a parasitic infection that can affect multiple organs, including the liver.