Portal Vein Bypass

Portal Vein Bypass

 

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. High pressure in the portal vein causes swelling and bleeding from blood vessels in the esophagus. This situation occurs when the liver is damaged from cirrhosis of the liver, a condition usually caused by prolonged, excessive alcohol consumption.
Massive internal bleeding caused by high pressure in the portal vein 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.

Precautions

Most patients who need portal vein bypass surgery not only have liver disease and poor liver function, but also suffer from an enlarged spleen, jaundice, and damage to the vascular system brought on by years of alcoholism. They are likely to experience serious complications during surgery. Some patients are aggressively uncooperative with medical personnel. Under these conditions, half the patients may not survive the operation.

Description

A choice of portal vein bypasses is available. Portal vein bypass is usually performed as an emergency operation in a hospital under general anesthesia. The surgeon makes an abdominal incision and finds the portal vein. In portacaval shunting, blood from the portal vein is diverted into the inferior vena cava. This is the most common bypass. In splenorenal shunting, the splenic vein (a part of the portal vein), is connected to the renal vein. A mesocaval shunt connects the superior mesenteric vein (another part of the portal vein) to the inferior vena cava.
Portal pressure can also be reduced in a procedure called transvenous intrahepatic portosystemic shunt (TIPS). A catheter is threaded into the portal vein, and an expandable balloon or wire mesh is inserted to divert blood from the portal vein to the hepatic vein. The rate of serious complications in TIPS is only 1-2%. The operation cannot be performed at all hospitals, but is becoming the preferred treatment for reducing portal pressure.

Key terms

Cirrhosis — A chronic degenerative liver disease common among alcoholics.
Inferior vena cava — A large vein that returns blood from the legs, pelvis, and abdomen to the heart.
Portal vein — Formed by a fusion of small veins that end in a network of capillaries, the portal vein delivers blood to the liver.

Preparation

Standard preoperative blood and urine tests are performed, and liver function is evaluated. The heart and arterial blood pressure are monitored both during and after the operation.

Aftercare

The patient will be 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 follow a diet and medication schedule designed to reduce the risks of re-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. 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.

Normal results

The survival rate is directly related to the amount of liver damage patients have. The less damage, the more likely the patient is to recover. Cooperation with restrictions on alcohol and diet affect long-term survival.

Resources

Books

McPhee, Stephen, et al., editors. Current Medical Diagnosis and Treatment, 1998. 37th ed. Stamford: Appleton & Lange, 1997.