Portal hypertension is an increase in the blood pressure within a system of veins called the portal venous system. Normally, the veins come from the stomach, intestine, spleen, and pancreas which, merge into the portal vein, which then branches into smaller vessels and travels through the liver. If the vessels in the liver are blocked, it is hard for the blood to flow causing high pressure in the portal system.
When the pressure becomes too high, the blood backs up and finds other ways to flow back to the heart, where it is pumped to the lungs, where it gets rid of waste products and picks up oxygen. The blood can travel to the veins in the esophagus (esophageal varices), in the skin of the abdomen, and the veins of the rectum and anus to get around the blockages in the liver.
Portal venous system connects stomach, gut, pancreas, spleen and liver. It carries a large volume of blood and is connected to the system circulation.
In liver disease there is necrosis of liver cells and hardening of tissues. So, the large volume of blood cannot pass through easily. It therefore passes into the systemic circulation, by-passing the liver. Thus any toxins or microbes present will reach the general circulation. The hardened liver tissues create resistance, preventing the blood from flowing easily and thus raise the pressure. The increased pressure also causes enlargement of connected blood vessels especially in the esophagus leading to the formation of esophageal varices which are prone to rupture and bleeding.
Ascitis or accumulation of fluids in the abdomen is another clinical feature of cirrhosis.
In cirrhosis, albumin synthesis by liver is decreased, leading to a lowering of serum albumin and therefore of plasma pressure. This increases portal hypertension leads to vasodilation and sodium retention causing ascitis. As fluid accumulates in the abdomen, the blood volume decreases and the blood flow to the kidney decreases. This stimulates the secretion of ADH and Aldosterone leading to further sodium and water retention.
Cirrhosis leads to increased energy expenditure, peritonitis and sometimes to Hepato renal syndrome.
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