Portal Hypertension Overview

Portal hypertension is a condition caused by liver disease. It's a type of high blood pressure (hypertension), but instead of affecting the entire body, it mostly affects the portal veins leading from the intestines to the liver. It's a significant complication of alcoholic hepatitis and liver cirrhosis and can cause swelling and bleeding.

Blood Flow Through the Liver: How It Works

The liver receives blood from two sources. Fresh blood, coming from the heart, supplies the needs of the liver itself. Also, because the liver filters toxins and processes nutrients, blood from the intestines and other organs of the digestive system comes in via the portal vein. The blood in the portal vein flows directly into the liver and is able to interact with the hepatocytes (liver cells). The blood continues through the liver and returns to the heart and lungs through a different set of vessels, the hepatic veins.

If the pathway to the liver from the intestines is blocked or slowed because of some obstruction, then the pressure increases in the portal venous system. This has been explained to me by imagining the portal venous system as a garden hose and the obstruction as a kink in the hose. You know from experience that pressure increases in the water. The same thing can happen in our bodies, except that, unlike the water hose, our veins can leak when pressure builds. This "leaking" is what contributes to ascitic fluid and is the cause of ascites, or fluid build-up.

What Causes the Obstruction

Liver cirrhosis can cause extensive fibrosis. Fibrosis is the most common cause of portal hypertension, though there are several other causes (such as schistosomiasis, sarcoidosis, portal vein thrombosis, toxicity from vinyl chloride or medications, cancer occluding the intrahepatic portal vein, sarcoidosis, and miliary tuberculosis). The intensive scarring of fibrosis obstructs the passage of fluids through the liver. Using our analogy above, the fibrosis is the "kink in the hose." The fibrosis surrounds the vessels within the liver which makes it more difficult for the blood to flow. As the blood and fluids try to filter through the obstructed liver, the pressure builds in the portal system, leading to further problems.

Problems Caused by Portal Hypertension

The most significant problems associated with portal hypertension are ascites (the accumulation of excess fluid in the tissues lining the organs and the abdominal wall) and varices (engorged veins along the esophagus, stomach or intestines caused by backed-up blood flow).

Varices are directly caused by portal hypertension. When the blood flow in the liver is obstructed, the blood can become backed up into the intersections of the portal venous system (the system of veins transporting blood between the digestive system and liver) and the systemic venous system (the system of veins that returns blood to the heart). The intersections of these two systems are small, fragile blood vessels called capillaries. These vessels are not able to withstand the increased blood pressure and become engorged or dilated. Such vessels can be seen along the surface of the esophagus or stomach during a procedure known as an endoscopy. They are fragile and at risk for bleeding.

Dangers

Yes, because portal hypertension can cause bleeding. In many cases, these bleeding episodes are considered medical emergencies. The mortality rate of a first time bleed is around 40%; 70% of people will re-bleed within a year with about a 30% mortality with subsequent bleeds. Esophageal varices are very common in people with advanced cirrhosis and it is estimated that one out of every three people with varices will develop bleeding.

Diagnosis

Anyone with advanced cirrhosis will be monitored closely for developing portal hypertension, which is usually diagnosed by the presence of one or more of the following:

• Thrombocytopenia
• Splenomegaly (enlarged spleen)
• Encephalopathy
• Having one of the complications of portal hypertension (ascites and esophageal varices)