Overview of Peritoneovenous Shunt
A peritoneovenous shunt (PVS) is a medical device that creates a passage from space surrounding your organs (the peritoneal cavity) to a large vein in your body, usually in your neck or upper chest. It consists of a tube placed beneath the skin with a one-way valve that ensures fluid only flows in one direction. This device helps drain excess fluid from the area around your organs into your bloodstream.
This technology was first brought forth by a man named Harry H Leveen and his team back in 1974. Since then, various versions of the device have been used in hospitals to help manage a health condition called chronic refractive ascites.
Ascites refers to the buildup of more fluid than normal in the peritoneal cavity, a symptom that can occur due to the body producing too much fluid or not being able to drain enough fluid. The PVS device works thanks to a pressure difference between the peritoneal cavity (which has high pressure due to the accumulated fluid) and the central veins of the body (which have lower pressure). When the pressure difference reaches about 30 to 50 millimeters of water (a unit of pressure), fluid can flow through the shunt from the peritoneal cavity to the vein. If the pressure drops below 30 millimeters of water, the one-way valve closes, stopping any blood from flowing back into the vein end of the tube.
Why do People Need Peritoneovenous Shunt
Peritoneovenous shunts (PVS) are helpful for draining excess fluid in the belly, typically for people with a specific prolonged condition known as chronic refractory ascites. It involves the collection of fluid in the belly that doesn’t improve with normal treatment. PVS is usually used for patients who have serious liver problems that result in unmanageable ascites.
There are many reasons why someone might end up with chronic ascites that can’t be treated with normal medications. Diseases that we know can cause this issue are both acute and chronic liver problems, like cirrhosis. Other causes can be malignant ascites, which is caused by specific types of cancers including those of the breast, ovary, or colon. Other health conditions that can lead to this are congestive heart failure, long-term kidney disease, and portal vein thrombosis, which is a blood clot in the liver’s primary vein.
PVS has several uses and are typically the best choice for treatment in the following situations:
- People with malignant or cirrhotic ascites that haven’t responded to usual treatments or large volume paracentesis. This is a procedure to remove the fluid buildup in the belly.
- People with chylous ascites, a rare condition where fat from the digestive system becomes present in the ascitic fluid.
PVS is also considered for patients with a few more specific conditions. For example, if the patient doesn’t respond to water pills (diuretics), is not suitable for a liver transplant, or cannot have frequent fluid removal due to multiple abdominal surgical scars. PVS is also an option if the patient has an expected lifespan of more than three months, has no medical reasons for not having PVS, or if doctors are not available to perform frequent removal of the ascitic fluid.
When a Person Should Avoid Peritoneovenous Shunt
Generally, a patient should not undergo a procedure known as PVS if they experience a few specific health conditions. These include:
If a person’s kidneys have stopped working properly and they are on a treatment called dialysis, PVS could be too risky for them. The same applies if a person has a serious blood infection known as septicemia. If a person has a blood disorder that makes it hard to stop bleeding, called uncorrectable coagulopathy, PVS could also be too dangerous. The procedure might not be an option for people who are very overweight or people who have had an infection or surgery in the past that has caused partitions to form in the large cavity in their abdomen.
There are absolute reasons to avoid placing a type of device called a Denver shunt, which is used to move fluid from the abdomen to other parts of the body in certain conditions. These reasons include bloody ascites, which is a condition where the abdomen fills up with bloody fluid, kidney failure, a history of certain types of veins bleeding, severe esophageal veins, congestive heart failure, pulmonary edema which happens when too much fluid collects in the lungs, liver failure that results in high bilirubin level (a substance the liver makes), blood clotting disorders, a history of peritonitis (which is an infection of the lining of the abdomen), poor physical health, low serum albumin level which is a protein made by the liver, and evidence of non-sterile ascites which is a condition where the abdomen fills up with fluid.
There are relative contraindications i.e., reasons to be cautious about the placement of a Denver shunt in patients with controlled congestive heart failure, loculated ascites which is a condition where pockets of fluid form in the abdomen, disease of the peritoneum which is the lining of the abdomen, massive pleural effusion which is an abnormal amount of fluid around the lung, non-bleeding varices which are enlarged veins, portal hypertension which is high blood pressure in the vein that carries blood from the intestines to the liver, and simultaneous gastrointestinal surgery.
Equipment used for Peritoneovenous Shunt
There have been many changes over time to the original design of the devices used for a procedure called Peritoneovenous shunting. Key variations include the Hyde shunt, Laveen shunt, and most commonly used, the Denver shunt. This device includes two flexible silicone tubes connected by way of a compressible pump.
Different sizes of the device, 11.5 French (F) and 15.5F, are available. The pump can either have a single valve or double valves, which open when there’s a pressure change of more than 3 cm of water from one end of the shunt to the other.
The flow of bodily fluids through the device can change depending on the size of the shunt and the pump valve. The single-valve device generally has a higher flow rate for both size options. However, the 15.5F device with double valves is most often used given its likelihood to not get clogged or cause fluids to flow backward.
Who is needed to perform Peritoneovenous Shunt?
An Interventional radiologist, along with a nurse and a radiology technician, is responsible for performing the procedure. These are trained medical professionals who have taken extensive classes and training to master the process. The Interventional radiologist is a specialist doctor who uses imaging techniques such as X-rays to guide small instruments through blood vessels and other pathways to treat diseases. While the nurse and radiology technician assist throughout the procedure. Together, they make sure your procedure goes smoothly and safely.
Preparing for Peritoneovenous Shunt
Before the medical procedure, the doctor will perform several tests. These include a complete blood count, a test to check how well the blood clots, and checks on kidney function (blood urea nitrogen and creatinine) and liver function (liver function tests). Another test measures albumin, a kind of protein in your blood. The doctor also takes a small amount of the fluid in your belly (ascites) with a thin needle (paracentesis) to examine it.
The doctor looks at various elements in this fluid, including the number of certain white blood cells (polymorphs), protein and albumin levels, and if any bacteria grow when the fluid is cultured. One important measure the doctor calculates is the serum-ascitic fluid albumin gradient (SAAG). This calculation helps figure out why there is too much fluid in your belly. If the SAAG value is more than 1.1 g/dl, it means that cancer is likely not the reason for the belly fluid.
To prevent the risk of infection, the doctor will give you an antibiotic that treats a wide range of bacteria (a broad-spectrum antibiotic). This drug is usually given through a vein before the procedure and then for a week afterward. You will be sedated enough to feel relaxed and comfortable (moderate sedation) for the procedure. This is typically done in a clinic or an outpatient part of a hospital, meaning you don’t have to stay overnight in the hospital.
How is Peritoneovenous Shunt performed
The Denver shunt is commonly used for draining excess fluid from the body. This procedure starts with the doctor preparing you for the procedure by cleaning and covering the region of interest. The doctor inserts a special tube (an All-Purpose Drainage catheter) into the upper part of your abdomen to drain excess fluid. This is then replaced by the one end of the Denver shunt after filling it with warm salt solution.
Moving on, the doctor secures this part of the shunt between the right part of the liver and the ribs. The doctor then makes a second cut on the lower part of your rib cage to put in a particular pump (part of the Denver shunt). The pump needs to be positioned against a solid, stable rib to work properly. Lastly, a third cut is made so that the doctor can create a passageway for the shunt towards the neck. This is ideally done beneath the skin but can also be done through the skin.
The shunt has a ‘venous end’ which is put inside a large vein leading to your heart either through neck veins or a vein beneath your collarbone. The doctor uses a special X-ray guidance (fluoroscopy) to make sure the tip of the shunt stops near the entrance of the right upper chamber of your heart. The doctor also attaches a one-directional device called a valve to keep blood from flowing back into the shunt. This way, the shunt can perform its purpose efficiently.
Possible Complications of Peritoneovenous Shunt
After getting a procedure called PVS, many patients can face potential problems. These could include infection in the abdominal lining, uncontrolled bleeding from expansive veins, blood clots in a large vein of the heart, fluid in the lungs, or even a potentially harmful clotting disorder known as disseminated intravascular coagulation (DIC). Other issues could include scar tissue forming, the shunt (part of the PVS) breaking, being blocked or leaking, a collapsed lung, or air trapped in the abdomen.
The most commonplace issue with PVS is shunt blocking. A study found that at the two-year mark, only about 18.6% of the shunts remained open.
Roughly 9% of individuals have reported DIC, a harmful clotting situation, after having the shunt inserted. This issue could be linked to specific triggers, like something known as tissue factor (TF), which kickstarts the process of blood clot formation.
Another uncommon incident might be blood clots forming in the shunt, most commonly at the tip. Additionally, certain types of bacteria including Staphylococcal and gram-negative organisms can cause infections during the operation. These infections can potentially lead to more serious conditions, like inflammation of the abdominal lining or a full-body infection, known as sepsis.
What Else Should I Know About Peritoneovenous Shunt?
Refractory ascites is a condition that often affects people with chronic liver disease, causing fluid to build up in the stomach. A common treatment for this condition is the insertion of a device called a Peritoneovenous Shunt (PVS). This procedure is proven to be quite effective and tends to significantly improve the patient’s quality of life.
Getting a PVS shunt inserted is relatively straightforward. All parts of the shunt are placed under the skin, which makes it possible for patients to get back to activities such as swimming and bathing – something they would not be able to do if they had some other types of drainage catheters that need to remain outside the skin.
Another advantage of this shunt is that it redirects the fluid from the stomach back into the bloodstream, rather than discarding it. This is beneficial because it ensures that your body does not lose essential nutrients, helping to prevent malnutrition, which can often be a concern in people dealing with long-term illnesses.
