Portal Vein Bypass Health Article

Definition

Portal vein bypass surgery diverts blood from the portal vein into another vein. It is performed when pressure in the portal vein is so high that it causes internal bleeding from blood vessels in the esophagus.

Purpose

The portal vein carries blood from the stomach and abdominal organs to the liver. It is a major vein that splits into many branches. In people with liver failure and cirrhosis, a chronic degenerative liver disease causing irreversible scarring of the liver, the liver is incapable of processing blood from the bowels. As a result, an abnormally high pressure develops in the veins that drain blood from the bowels as the body tries to form other channels for the blood to empty into the main circulation. These channels consist of fragile veins that surround the esophagus, stomach, or other areas of the digestive tract. Because of the fragility of these veins, they are prone to rupturing, which can result in massive amounts of bleeding. The abnormally high pressure within the veins draining into the liver, called portal hypertension, can also result in the formation of fluid seeping from the surface of the liver and collecting in large quantities in the abdominal cavity, a condition known as ascites.

Massive internal bleeding caused by portal hypertension occurs in about 40% of patients with cirrhosis. It is initially fatal in at least half of these patients. Patients who survive are likely to experience bleeding recurrence. Portal vein bypass, also called portacaval shunting, is performed on these surviving patients to control bleeding.

The purpose of portal vein bypass surgery is to lower portal hypertension by shunting blood away from the portal venous system and into the main venous system.

Demographics

Cirrhosis of the liver is caused by chronic liver disease. Common causes of chronic liver disease in the United States include hepatitis C infection and long-term alcohol abuse. Men and women are equally affected, but onset is earlier in men.

Description

Different portal vein bypass procedures are available. The surgery is usually performed under general anesthesia. The surgeon makes an abdominal incision and locates the portal vein. In portacaval shunting, blood from the portal vein is diverted into the inferior vena cava (one of the main veins leading back to the heart). This is the most common type of bypass. In splenorenal shunting, the splenic vein (a part of the portal vein) is connected to the renal (kidney) vein. A mesocaval shunt connects the superior mesenteric vein (another part of the portal vein) to the inferior vena cava.

Another procedure, called transvenous intrahepatic portosystemic shunt (TIPS), has become the favored surgical approach. A TIPS is performed through a small nick in the skin, working through specialized instruments that are passed through the body using an x ray camera for guidance. The TIPS procedure creates a shunt within the liver itself, by linking the portal vein with a vein draining away from the liver together with a device called a stent, which acts as a scaffold to support the connection between these two veins inside the liver.

Diagnosis/Preparation

A radiologist assesses patients for bypass surgery based on their medical history, physical examination, blood work, and liver imaging studies performed using computed tomagraphy (CT) scans, ultrasounds, or magnetic resonance imaging (MRI) scans, and in consultation with the treating gastroenterologist, hepatologist, or surgeon.

Standard preoperative blood and urine tests are also performed. The heart and arterial blood pressure are monitored both during and after the operation.

Aftercare

The patient is connected to a heart monitor and fed through a nasogastric tube. Vital functions are monitored through blood and urine tests. Patients receive pain medication and antibiotics. Once released from the hospital, patients are expected to abstain from alcohol and to follow a diet and medication schedule designed to reduce the risks of bleeding.

Risks

Portal vein bypass surgery is high risk because it is performed on patients who are generally in poor health. Only half the patients survive, although the chances of survival are greater with TIPS surgery. The rate of serious complications in TIPS is only 1–2%. Those patients who survive the operation still face the risk of heart failure, brain disease due to a decrease in the liver's conversion of waste products (liver encephalopathy), hemorrhage, lung complications, infection, coma, and death.