Overview of Portacaval Shunt
Surgical shunts were once more commonly used in medicine, but new advancements have led to a decrease in their use. These advancements include endoscopic therapy, a medical procedure that involves inserting a long, flexible tube into the body to observe or treat an internal organ or tissue in detail, and TIPS (transjugular intrahepatic portosystemic shunt) procedures, which create a pathway in the liver to move blood more easily. However, surgical shunts are still a treatment option in certain cases, such as in patients who have hard-to-treat variceal bleeding (internal bleeding often related to increased blood pressure in the veins of the esophagus and stomach), or in patients with portal hypertension (high blood pressure in the liver).
Surgical shunts, which are categorised as selective, partial, or total, can reduce pressure in the gastroesophageal varices (swollen veins in the lower part of the esophagus) and the portal system (veins carrying blood to the liver). However, the types of shunts vary in terms of the amount of blood flow they allow to the liver.
When choosing a shunt, the surgeon considers their own familiarity with the procedure, and the specific structure of the patient’s veins. For instance, total portosystemic shunts connect the body’s circulation system with the liver’s circulation system. These shunts can stop variceal bleeding and help to control ascites (accumulation of fluid in the abdominal cavity), which is helpful for the patient. However, one downside is that these shunts may cause blood to bypass the liver, which carries out important metabolic functions. This can potentially lead to hepatic encephalopathy (a decline in brain function that occurs as a result of severe liver disease), as well as sudden liver failure.
It’s important to note that portocaval shunts (connecting the portal vein, which carries blood from the digestive organs to the liver, and the inferior vena cava, which carries blood from the lower half of the body back to the heart) are not recommended for patients who may need a liver transplant in the future. That’s because scarring can make the transplant operation more complex. In fact, portocaval shunts are associated with the development of a sclerotic portal vein (portal vein hardening), which increases the difficulty of surgery for a liver transplant.
Why do People Need Portacaval Shunt
A portacaval shunt is a surgical procedure that creates a new pathway for blood flow to your liver. It’s mainly used to control severe upper digestive system bleeding from abnormal veins (varices). These abnormal veins usually occur when blood flow to your liver is blocked, causing the blood to back up into other blood vessels like those in your esophagus. This blockage can cause these vessels to enlarge and potentially rupture, leading to life-threatening bleeding. Although there are various other treatments to control varices, like endoscopic (using a thin tube with light and camera) treatments, sometimes these are not available or not effective. In these cases, a portacaval shunt might be recommended as the preferred choice.
This procedure is particularly beneficial in cases where a patient had a spleen removal surgery (splenectomy), had a clot in the splenic vein (splenic vein thrombosis), after a splenorenal shunt (a connection between the splenic vein and the kidney), fluid accumulation in the abdomen (ascites), reversed blood flow in the portal vein, or clots in the hepatic veins.
The portacaval shunt is also used for the treatment of portal hypertension, a condition where the blood pressure within the liver is unusually high. This elevated pressure, which is more than 5 to 10 mmHg, can result from various conditions. In the US, cirrhosis, or scarring of the liver, is related to about 90% of portal hypertension cases. Other causes include the presence of blood clots, abnormal blood connections, and diseased enlargement of the spleen. The condition may also result from conditions like primary biliary cirrhosis, liver diseases, polycystic liver disease, and venous-occlusive disease. Certain other conditions like Budd-Chiari syndrome, inferior vena cava webs or thromboses, congestive heart disease, and constrictive pericarditis can also give rise to portal hypertension.
Conditions of portal hypertension often lead to varices, which can cause severe bleeding. In some situations, bleeding from these varices can account for severe disease and fatality. When these varices are not properly managed, each episode of bleeding carries a mortality risk of around 20%. Admission to ICU for monitoring, resuscitation, and ultimate treatment is critical. This is best achieved by airway protection with an oxygen tube if compromised, large vein access for blood products, antibiotic prevention for infections, and medications like octreotide to control bleeding. Also, once the initial episode of hemorrhage is controlled, preventive measures to mitigate recurrent bleeds should be initiated straight away.
An emergency esophagogastroduodenoscopy (EGD) is a critical test when suspecting an acute variceal bleeding. EGD enables the physician to identify varices or in ruling out other sources of bleeding. If left untreated, the patient is at significant risk of rebleeding. To reduce this risk, nonselective beta-blockers, propranolal and nadolol, along with endoscopic variceal band ligation, a procedure where the varices are tied off at the top, can be used. If these measures fail, surgical shunting and certain other techniques may be sought to manage the situation.
Another aspect of managing an actively bleeding patient is ensuring the patient’s blood levels are managed effectively. This could mean administering certain medications into the vein or through a specialized artery infusion. It is also important to clear the digestive tract of any old blood which might complicate exposure and increase the risk of ammonia poisoning, achieved by administering nonabsorbable antibiotics and restoring blood volume with blood products, albumin, and lactated Ringer solution.
A transjugular intrahepatic portacaval shunt (TIPS) is another treatment option. This is when a tract is created between the portal vein and hepatic vein and kept open with a metal stent. This helps to alleviate pressure in the liver. Indications for side-to-side portacaval shunts can then be identified after substantial bleeding has been controlled.
When a Person Should Avoid Portacaval Shunt
If a patient is going through a procedure called portacaval shunt, this means their liver’s function at the time of the procedure is essential. In simple terms, a portacaval shunt is a surgical connection made between the large vein going in the liver and a vein taking blood to the heart. A golden rule doctors follow is to boost a patient’s nutrition and liver’s condition before surgery. This may involve a few weeks of managing their diet, increasing their physical activity, and even using medicine to decrease the amount of water in the body, called diuretics.
Assessing the liver’s functionality is a crucial step, which usually involves a combination of physical check-ups and lab tests. The decision to undergo the shunt procedure is typically based on the openness of the portal and splenic veins (that is, whether blood can flow freely), liver function tests, and other clinical factors.
The best candidates for shunting are usually under 60 years old with no signs of serious liver disease. This disease can show up as mental confusion, fluid buildup in the belly, yellowish skin and eyes, or significant weight loss due to muscle wasting. If someone has a history of these symptoms, their surgical risk is higher. Normal levels of platelets (which help clot the blood) and PTT (a test that measures how long it takes blood to clot) are also important. If these values are outside their normal range, doctors will try to correct them through transfusion of blood, fresh frozen plasma (which contains clotting factors), albumin (a protein made by the liver) or vitamin K.
If the patient’s fluid buildup in the belly is severe, they might need to take diuretics. Furthermore, any electrolyte (substances like sodium, potassium that help your body function) and acid-base imbalances should be managed, especially if the patient has low levels of potassium and a condition called alkalosis. Any clotting issues not related to the protein prothrombin, which helps blood clot, can usually be corrected using fresh frozen plasma and platelet concentrate.
Before surgery, the patient will be typed (determine their blood type) and screened, and there should be 10 to 12 units of whole blood ready for the surgeon. The levels of albumin, a liver-made protein, should be above 3 g/dL when assessing the patient’s nutritional status. Sodium sulfobromophthalein is a compound used in diagnosing liver functionality and should be below 30% in the 30 minutes test.
All these specific criteria are essential, and any deviations from them could increase the patient’s risk during surgery since such changes often indicate the worsening of the liver’s function. In certain circumstances, a liver transplant might be necessary.
There are three different types of shunts used to manage high blood pressure in the portal vein – the large vein going to the liver; namely portocaval, splenorenal, and mesocaval shunts.
The patient’s evaluation might also include endoscopies (procedures that provide a view of the digestive tract’s inner side), barium studies (imaging tests using a barium-based contrast material to visualize the digestive tract), and imaging studies to assess the liver’s blood flow. A radionucleotide scan can provide an idea of the total blood flow towards the liver. Hepatic vein catheterization – a procedure where a needle and a thin tube, the catheter, are used to access the liver’s veins – can determine the amount of blood flow and the pressure in the portal vein.
The best source of estimating the portal vein’s pressure is a test known as splenoportography, a procedure that uses x-rays to visualize the spleen’s veins. To safely carry out this study, the patient’s prothrombin time needs to be within normal limits, and there should be an operating room immediately available, just in case any severe bleeding develops. This procedure can reveal the extent of the high pressure in the portal vein and the severity of the compromised blood flow to the liver. The results from all these studies will guide the surgeon on the choice of shunt to be performed.
Preparing for Portacaval Shunt
A portacaval shunt surgery requires general anesthesia. This means you’ll be completely asleep and unaware of the procedure. Some risks come with anesthesia, such as low oxygen levels (hypoxia) and low blood pressure (hypotension). In some cases, if your liver isn’t working properly, the doctors can’t use certain types of anesthesia because they could make your condition worse. But other common anesthetics and muscle relaxants don’t typically cause any problems for the liver. The surgical team will also ensure that they have fluids and blood products at the ready in case they need to be given quickly during surgery.
In preparing for the surgery, the surgical team will position you on your right side and lift it to a 30-degree angle. This specific position expands the right side of your rib cage into the flank area (side and back area between the ribs and hips), providing better surgical access. The surgical bench will be adjusted to provide more space between the right hip and the lower edge of the ribcage. This is done so the doctors can perform the surgery via a long incision in the right lower rib area. If the doctors haven’t decided if a portocaval shunt or a splenorenal shunt (another kind of bypass surgery) will be performed, you might be placed on your back so that the initial incision can be expanded in the correct direction once the decision is made.
As part of the preparation for the operation, the surgical team will clean the skin from above the nipples to well below the pubic bone. Particular attention will be paid to the left side of your chest, as sometimes the surgical cut may need to be extended into the chest area.
How is Portacaval Shunt performed
The doctor will make a cut on the right side just below the ribs that extends out towards the side of your abdomen. There can also be a cut right in the middle of the stomach reaching up to the bone at the bottom of your sternum. Once inside your abdomen, the doctor will thoroughly examine everything. They will then need to confirm if the blood pressure in the portal vein (the large vein that carries blood from your intestines and spleen to your liver) is high. High blood pressure in the portal vein is a sign of a condition called ‘portal hypertension’. They can do this by placing a small tube in a vein near the stomach and measure the pressure.
If a scan done before the surgery has identified a suitable portal vein, they begin the next part of the surgery. If not, the doctor will first isolate the portal vein and will do a type of X-ray called a portal venogram to carefully examine it before moving on. Once in your abdomen, they will place devices that help to keep the abdomen open and allow a clear view of the work area. Then, they make a careful cut to open the lining covering a large vein (inferior vena cava) near the back of your abdomen. Any tissue covering the vein will be carefully removed and the vein will be isolated by gently, yet precisely, cutting away from the kidneys where it lies at the back. This process will include managing other veins such as adrenal, lumbar and hepatic veins from the liver using fine silk bands.
The doctor will also need to deal carefully with an area at the back where veins might be enlarged due to increased pressure. The inferior vena cava will then be fully exposed for the doctor to work on. If necessary, they can remove some of the liver to give them more room to work. Any bleeding is controlled with fine silk stitches before and after making the cut in the liver.
With great care, the doctor will observe and identify the portal vein within an area of your liver. A useful method during this part of the surgery can be to wrap a tape or rubber tissue drain around the common bile duct (a tube that carries bile from your liver to the small intestine). This will help to clearly see the portal vein. During this stage, they should protect nearby tributaries to the pancreas and ensure that the vessels are clear enough for them to bring the portal vein closer to the inferior vena cava.
The inferior vena cava needs to be completely free and mobile so it can move upwards towards the portal vein. If the doctor is not able to do so, the procedure may not be successful as the gap between the two vessels might be too large. A similar mobility is also required for the portal vein and the doctor might need to carry out more dissection to get it right. If the two veins are comfortably brought together without much tension, the doctor may proceed to the next stage.
In the final stage, the doctor will carefully proceed to divide some tissues and tie off some tributaries to the portal vein. They will also make sure that the vein is properly cleared for the next step of the procedure. The doctor will then check the pressure in the portal vein and the inferior vena cava. High pressure in these vessels indicates portal hypertension. Finally, non-crushing clamps will be applied to the portal vein to prepare it for the next part of the surgery.
Possible Complications of Portacaval Shunt
After surgery, it’s very important to make sure the patient gets enough oxygen. Usually, doctors will give oxygen for the first 24 to 48 hours after the operation. They will also regularly check the patient’s blood count and pressure to make sure they have enough blood volume. This is particularly important in surgeries involving connections between the portal and caval veins (portocaval shunts), which have a high risk of causing a condition called hepatic coma. To lower this risk, it is important to keep protein breakdown in the body as low as possible after the surgery.
During the recovery phase, there’s a period when the patient can’t eat or drink anything (NPO). During this time, they need at least 200 grams of carbs each day to avoid unnecessary breakdown of protein. When the patient can start eating again, their protein intake should be started at low levels, around 30 grams a day. If they handle this well, the amount of protein can be gradually increased every two days until they’re eating 50 to 75 grams of protein per day. Keeping an eye on blood ammonia levels can help check if the body is handling the increased protein. If signs of decreased liver function appear, the protein intake should be reduced and the patient might need to take antibiotics that act in the intestine. Their ability to form blood clots can be checked with a test called prothrombin activity, and sometimes vitamin K might be given.
Vitamins can also be beneficial after surgery, but a percentage of patients develop a condition called ascites. This condition, which results in a fluid build-up in the belly, can cause problems if not managed. To prevent or lessen this condition, doctors will monitor and possibly limit the amount of fluid and sodium the patient takes in. If ascites does occur, it can be managed by strictly limiting sodium and also by giving medicines that help the body get rid of extra fluid (diuretics). Peptic ulcers, which are sores in the lining of the stomach, are more common after a portacaval shunt procedure, so heartburn medicine such as low-sodium antacid therapy and medicines that lessen stomach acid (proton pump inhibitors) may be given.
