Peritoneovenous shunt

Definition

A peritoneovenous shunt refers to the surgical insertion of a shunting tube to achieve the continuous emptying of ascitic fluid into the venous system.

Purpose

Ascites is a serious medical disorder characterized by the pathological accumulation of fluid in the peritoneal cavity, the smooth membrane that lines the cavity of the abdomen and surrounds the organs. Ascites is usually related to acute and chronic liver disease (cirrhosis) and to a lesser degree, to malignant tumors arising in the ovary, colon, or breast. Ascites may also be associated with chronic kidney disease and congestive heart failure. The formation of ascitic fluid results from the interplay of three factors: abnormally high pressure within the liver or the veins draining into the liver (portal hypertension); abnormally low amounts of albumin in the blood (hypoalbuminemia); and changes in sodium and water excretion by the kidneys.

When medical therapy fails, peritoneovenous shunts help manage chronic ascites.

Demographics

Cirrhosis is the seventh leading cause of death by disease in the United States, killing over 25,000 people each year. Fifty percent of patients with cirrhosis will develop ascites over a period of 10 years. Cirrhosis—regardless of its cause—greatly increases the risk for liver cancer. Few studies have been conducted on the risk for liver cancer in patients with primary biliary cirrhosis; however, one study reported an incidence of 2.3%. Approximately 4% of patients with cirrhosis caused by hepatitis C develop liver cancer. In Asia, about 15% of people who have chronic hepatitis B develop liver cancer, but this high rate is not seen in other parts of the world. One Italian study that followed a group of hepatitis B patients for 11 years found no liver cancer over that period of time.

Description

A variety of shunts have been designed for peritoneovenous shunting, including the Hyde shunt (1966-1974), LaVeen shunt (1974-1980), and Denver shunt. The latter predates the LaVeen shunt, but is more popular as of 2003. All designs work about equally well.

For the peritoneovenous shunt insertion procedure, the patient only requires a local anesthetic and a sedative. A long needle is inserted into the jugular vein in the neck, and is passed down through the superior vena cava, the large vein that delivers blood from the head, neck, and upper limbs back to the heart. This serves to widen the vein. The surgeon makes an incision and inserts a tube traversing the subcutaneous tissue of the chest wall. The tube connects the peritoneal cavity to the neck, where it enters the widened jugular vein. There the surgeon attaches a pressure-sensitive one-way valve to prevent backflow.

Diagnosis/Preparation

Ascites may go unnoticed for quite some time until the patient notices a slight increase in waistline. Severe ascites with marked abdominal distension becomes very disabling, especially when associated with swelling of the legs, pleural effusions (fluid around the lungs), and shortness of breath.

Diagnosis can be established by examination of the ascitic fluid, which allows the physician to differentiate between cirrhosis and tumor-induced ascites. The fluid is taken from the peritoneal cavity in a procedure called a paracentesis . Ascitic fluid analysis includes a total polymorph count, protein and albumin concentrations, and placement of at least 10 ml of ascitic fluid each into blood culture bottles for processing. If a measurement called the serum-ascitic fluid albumin gradient is greater than 11 g/L, cirrhosis, not cancer, is suspected.

Aftercare

After surgery, the patient's vital signs are monitored in a recovery room . Pain medication and antibiotics are administered as needed. Once released from the hospital, the patient is expected to abstain from alcohol, and follow a low-salt diet and medication regime designed to control ascites.

Patients also require training in shunt maintenance. To keep the fluid moving out of the abdomen, the shunt has to be properly pumped on a daily basis. Twice a day—once at bedtime and again prior to rising in the morning—the shunt is pumped about 20 times. This is essential to limit the accumulation of fibrin and other debris within the shunt, and to avoid the formation of an occlusive fibrin sheath at the venous tip.

Risks

Complications following peritoneovenous shunt insertion are common and include infection, leakage of ascitic fluid, accumulation of abnormally large amounts of fluid in the intercellular tissue spaces of the body (edema), deregulation of the blood clotting mechanism (coagulopathy), and shunt blockage. Clogging of the shunt with debris is the most common complication. Some patients develop further complications from the ascitic fluid entering directly into their bloodstream. Often, scar tissue develops, making future liver transplants difficult.

Normal results

In spite of the complications associated with the procedure, many patients obtain useful relief from ascites following peritoneovenous shunt insertion.

Morbidity and mortality rates

The most recent guidelines from the American Association for the Study of Liver Diseases recommend peritoneovenous shunting only under these conditions:

• Patient is diuretic-resistant, and is not a transplant candidate.
• Patient is not a candidate for serial therapeutic paracentesis because of multiple abdominal surgical scars.
• A physician is unavailable to perform serial paracentesis.

Cirrhosis is irreversible, but the rate of progression can be very slow depending on its cause and other factors. Five-year survival rates are about 85% in the Unites States and can be lower or higher depending on severity.

Alternatives

Alternative treatments for ascites include:

• Diuretics . Diuretics are medications that promote the excretion of urine and help eliminate excess fluids. The treatment of ascites always involves restricting dietary salt and taking diuretic pills to increase the output of salt in the urine. This treatment is effective, at least in the short-term, in 90% of patients.
• Repeated large-volume paracentesis. This approach, also called serial paracentesis, features repeated surgical puncture of the abdominal cavity and aspiration of the ascitic fluid.
• Transjugular portosystemic shunt. A shunting procedure designed to relieve portal hypertension.
• Portocaval shunt. Another shunting procedure designed to relieve portal hypertension.
• Liver transplantation . Replacement of the patient's liver by one obtained from a donor. Liver transplantation is the only definitive treatment for ascites, and the only treatment that has been clearly shown to improve survival.

There is no satisfactory treatment for refractory ascites in patients with cirrhosis. Both peritoneovenous shunts and paracentesis have been used, but there is uncertainty about their relative merits.

See also Portal vein bypass.

Resources

books

Arroyo, V., P. Gines, J. Rodes. and R. W. Schrier, eds. Ascites and Renal Dysfunction in Liver Disease: Pathogenesis, Diagnosis, and Treatment. Oxford, UK: Blackwell Science Inc, 1999.

Moore, W. S. ed. Vascular Surgery: A Comprehensive Review. Philadelphia: W. B. Saunders Co., 2001.

periodicals

Gines, P., and V. Arroyo. "Hepatorenal Syndrome." Journal of the American Society of Nephrology 10 (1999): 1833-9.

Hu, R. H. and P. H. Lee. "Salvaging Procedures for Dysfunctional Peritoneovenous Shunt." Hepatogastroenterology 48 (May-June 2001): 794-7.

Koike, T., S. Araki, H. Minakami, S. Ogawa, M. Sayama, H. Shibahara, and I. Sato. "Clinical Efficacy of Peritoneovenous Shunting for the Treatment of Severe Ovarian Hyperstimulation Syndrome." Human Reproduction 15 (2000): 113-17.

Orsi, F., R.F. Grasso, G. Bonomo, C. Monti, I. Marinucci and M. Bellomi. "Percutaneous Peritoneovenous Shunt Positioning: Technique and Preliminary Results." European Radiology 12 (May 2002): 1188-92.

Wagayama, H., T. Tanaka, M. Shimomura, K. Ogura, and K. Shiraki. "Pancreatic Cancer with Chylous Ascites Demonstrated by Lymphoscintigraphy: Successful Treatment with Peritoneovenous Shunting." Digestive Disturbance Science 10 (August 2002): 1836-8.

organizations

American Gastroenterological Association. 4930 Del Ray Avenue, Bethesda, MD 20814. (301) 654-2055. <www.gastro.org>.

Society for Vascular Surgery. 900 Cummings Center, Beverly, MA 01915-1314. (978) 927-8330. <svs.vasculaweb.org>.

other

"Ascites." Family Practice Notebook. <www.fpnotebook.com/GI35.htm>.

Monique Laberge, Ph.D.

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

Peritoneovenous shunt insertion is performed in a hospital by a surgeon specialized in gastroenterology or hepatology.

QUESTIONS TO ASK THE DOCTOR

• Is there any other treatment available for ascites?
• What are the risks associated with peritoneovenous shunting?
• How long will it take to recover from the surgery?
• How does the shunting mechanism work?
• How many peritoneovenous shunt procedures does the surgeon perform each year?
• Will further surgery be required?
• What happens if the shunt becomes blocked?

Peritoneovenous shunt

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.

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 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

Drake, J. M., and C. Sainte-Rose. Shunt Book. New York: Blackwell Science Publishers, 1995.

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

PERIODICALS

Bechstein, W. O., et al. "Peritoneovenous Shunting for the Treatment of Massive Ascites". New England Journal of Medicine 322 (1990): 1750-1756.

LeVeen, H. H. "The LeVeen Shunt." Annual Reviews of Medi cine 36 (1985): 453-469.

Lee, C. W., G. Boclek, and W. Faught. "A Survey of Practice in Management of Malignant Ascites." Journal of Pain and Symptom Management 16 (1998): 96-101.

Runyon, B. A. "Care of Patients with Ascites." New England Journal of Medicine 330 (1994): 337-342.

Monique Laberge, PhD

KEY TERMS

Abdomen

—The part of the body which lies between the diaphragm and the rim of the pelvis.

Circulatory system

—The circulatory system consists of the heart and blood vessels. It serves as the body's transportation system.

Esophagus

—The part of the digestive tract that brings food from the mouth to the stomach.

Jugular veins

—Large veins returning the blood from the head to the heart into two branches (external and internal) located on each side of the neck.

Lymph

—Colorless liquid that carries the white blood cells in the lymphatic vessels.

Lymphatic system

—A subsystem of the circulatory system, it consists of lymphatic fluid, lymphatic vessels, and lymphatic tissues (lymph nodes, tonsils, spleen, and thymus). It returns excess fluid to the blood and defends the body against disease.

Peritoneum

—Smooth membrane which lines the cavity of the abdomen and which surrounds the viscera (large interior organs) forming a nearly closed bag.

Peritonitis

—Inflammation of the peritoneum.

Vena cava

—Very large veins. There are two vena cava in the body. The superior vena cava returns blood from the upper limbs, head, and neck to the heart and the inferior vena cava returns blood from the lower limbs to the heart.

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?