peritoneovenous shunt: Definition from Answers.com Mobile

Peritoneovenous Shunt

Key Terms: Abdomen, Circulatory system, Esophagus, Jugular veins, Lymph, Lymphatic system, Peritoneum, Peritonitis.

Definition

A peritoneovenous shunt (PVS) is a device that is inserted surgically into the body to create a passage between the peritoneum (abdominal cavity) and the jugular vein to treat refractory cases of peritoneal ascites. Ascites is a condition in which an excessive amount of fluid builds up within the abdominal cavity.

Purpose

The abnormal build-up of fluid in the spaces found between the tissues and organs of the abdominal cavity is a common symptom of liver disease such as cirrhosis of the liver, but approximately 10% of the diagnosed cases occur as a side effect of several types of cancers, such as ovarian, gastric, exocrine pancreatic, and colorectal cancers, and lymphoma. This condition is known as ascites and it causes pain and discomfort in patients. When doctors can not treat advanced ascites with medication, they recommend an operation such as the PVS procedure as a means to empty the abdomen of the accumulated fluid.

The ascites that results from cancer contains high levels of proteins. It occurs because of functional imbalances in the cells of the organs affected by the cancer and because the walls of the capillaries containing the normal abdominal fluid start leaking. Depending on the type of cancer, there may also be a decrease in the ability of the lymphatic system of the body to absorb fluids.

Precautions

The PVS procedure is restricted to patients with livers that function normally. Additionally, the required veins must be healthy so as to allow the insertion of the shunt device. The PVS insertion is not performed in the following cases:

patients having undergone previous extensive abdominal surgery
patients diagnosed with bacterial peritonitis
patients with diseased veins in the esophagus
patients with heart disease
patients with a diseased major organ

In cases of ascites due to cancer (malignant ascites), there is a concern that the use of a PVS could enhance the spread of the cancer. In evaluating a cancer patient as a candidate for a PVS, the risk of cancer spread must be balanced against pain/discomfort relief, quality of life issues, and the expected survival period.

Questions to Ask the Doctor

What are the benefits of PVS for my condition?
Why is medication not possible?
What complications are possible?
What happens if the PVS device gets blocked?
How experienced is the surgeon with PVS surgery?

Description

The most common PVS device is the LeVeen shunt, used since the 1970s to relieve ascites due to liver disease and since the 1980s for cancer-related ascites. It consists of a plastic or silicon rubber tube fitted with a pressure-activated one-way polypropylene valve that connects the peritoneal space where the fluid is collecting to a large vein located in the neck called the jugular vein. The tube enters the jugular vein and terminates in another large vein called the superior vena cava that returns blood to the heart. Thus, the fluid goes from the abdominal cavity to the venous blood circulatory system and is then eliminated by the kidneys. The function of the one-way valve is to prevent blood from flowing back into the peritoneal space.

The PVS is inserted under the skin of the chest under local or general anesthesia, depending on the general health condition of the patient.

An alternative option to treat ascites due to cirrhosis is to use a transjugular intrahepatic portosystemic shunt (TIPS). This is also a tube that is passed through the skin of the neck and into the jugular vein but it is pushed all the way through the liver and into the portal vein, which drains into the liver. It thus creates a shunt of blood across the liver in an attempt to reduce pressure and fluid formation.

Preparation

Abdominal computed tomography (CT) scans are used to determine the extent of the ascites. Lab tests are usually performed to determine if the excess abdominal fluid is infected and other imaging studies such as ultrasound may be performed to assess the general condition of the veins selected for insertion of the PVS tube. For the operation, the patient is usually injected with a mild sedative and local anesthetic. The surgeon uses a puncture needle to create the opening required for insertion of the PVS device so as to avoid surgical incisions which take longer to heal.

Aftercare

Antibiotics are usually prescribed for approximately four days after surgery. Any fever or chills that the patient experiences should be reported to the doctor without delay.

Risks

Complications following PVS insertion are very common and include infection, leakage of fluid, fluid build-up in the lungs, problems with blood coagulation, heart failure and blockage of the PVS device.

Normal Results

The PVS insertion is considered successful when the abdominal fluid build-up gradually disappears after the operation.

Abnormal Results

The most common complication resulting from PVS insertion is obstruction of the valve or tube, which can be due to a blood clot or to scar tissue forming around the shunt and eventually blocking it. This complication occurs in approximately 60% of cases during the first year of follow-up.

Resources

Books

Grannis, F. W, et al. "Fluid Complications." In Cancer Management: A Multidisciplinary Approach. Melville, NY: Publisher Research & Representation, Inc., 2000.

—Monique Laberge, Ph.D.