The liver is one of the largest and most important organs in your body. As blood from the intestines passes through the liver, this vital organ processes and absorbs nutrients, metabolizes drugs, and removes toxins.
If your liver can’t purify intestinal blood before it moves through other organs, you can develop serious conditions. These include liver damage, hepatic encephalopathy, and bleeding.
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A portosystemic shunt (also known as a liver or hepatic shunt) is a rare medical condition in which blood from your digestive organs does not reach the liver.
The liver receives blood from two sources:
The hepatic artery delivers oxygen-rich blood from the heart
The portal vein moves blood from the spleen, stomach, pancreas, and intestines into the liver
Blood from the portal vein is rich in nutrients absorbed in the gastrointestinal tract, which the liver processes before the blood flows back into the heart through the hepatic veins.
A liver shunt is an unnatural connection that develops between the portal vein and systemic veins. The shunt causes blood to bypass the liver partially or completely, causing complications.
There are two types of liver shunts: Intrahepatic and extrahepatic.
Intrahepatic shunts occur when the connection forms inside the liver, especially in children. These are rare and display mild symptoms.
Extrahepatic shunts occur outside the liver and are more common.
Because of the liver's crucial role in metabolism, a liver shunt can cause serious health problems. In most cases, it arises with severe liver disease or cirrhosis, causing symptoms like:
Pulmonary hypertension (high blood pressure that affects blood vessels in the lungs)
Portal hypertension (high blood pressure that affects blood vessels in the liver)
Hyperglycaemia (excessive blood glucose)
Hyperammonemia (high levels of ammonia in the blood), which can be highly toxic
Hepatopulmonary syndrome (affecting oxygen absorption and blood vessels in the lungs)
Hypergalactosemia (excessive levels of galactose in the blood)
Gastrointestinal bleeding, which can cause bloody or black stools and vomiting blood
Ascites (accumulation of blood in the abdomen)
Low levels of platelets and white blood cells in the blood
In particular, liver problems can increase blood toxin levels. This can generate other issues, such as brain damage, kidney problems, and nervous system conditions.
A liver or portosystemic shunt can either be congenital (present at birth) or acquired. Congenital portosystemic shunts are extremely rare, occurring in only one of every 30,000–50,000 births.¹
Researchers believe congenital liver shunts develop due to abnormal fetal development. As the circulatory system develops, some vessels are supposed to disappear as more complex systems of veins and arteries grow. If some of these vessels fail to disappear or extra connections develop abnormally, a congenital hepatic shunt may occur.²
Congenital portosystemic shunt often occurs with other abnormalities, including heart and blood vessel defects.
On the other hand, portal hypertension may cause acquired liver shunts, which is high blood pressure in the veins carrying blood to the liver. These shunts develop to reduce pressure in the portal veins.
Spontaneous portosystemic shunts (SPSS) can occur with cirrhosis and liver failure, although portal hypertension still plays a significant role.
While shunts reduce pressure, they may cause other problems, including bleeding, thrombosis, and further liver damage.
A liver shunt causes what is often called portosystemic shunt syndrome (PSS). This syndrome can worsen as the liver function continues to deteriorate.³
Early-stage portosystemic shunt syndrome is characterized by relatively normal liver function. In this stage, you may have a few mild symptoms and likely no liver damage.
Late-stage PSS can occur after years, often leading to hepatic encephalopathy (HE). Increased toxins in the blood and nervous system cause HE, which can affect your brain and cause symptoms like confusion and mood changes.
You will also have reduced liver function during late-stage PSS and other symptoms. Due to liver damage, portal vein thrombosis may also occur at this point, further obstructing blood flow to the liver.
Terminal PSS follows if you don’t receive treatment to correct the condition. By this point, you'll experience liver failure, chronic hepatic encephalopathy, ascites, jaundice, and thrombocytopenia (low platelet count).
Liver shunt diagnosis relies on imaging technology, such as CT or MRI scans. It is especially relevant if you’re in the early stage and aren’t displaying any tell-tale symptoms.
Depending on your age, doctors may diagnose a portosystemic venous shunt using a combination of imaging, biochemical tests, and invasive tests. The diagnostic method also depends on your symptom and the possibility of treatment.
One diagnostic method is Doppler ultrasound, which can measure the volume of blood that passes through the shunt. Shunt flow that diverts more than 5% of the expected blood flow through the liver is considered significant.
Doctors can also conduct other tests to detect the various symptoms of a liver shunt and determine the severity of the condition. That includes tests for ammonia levels, galactose levels, and brain imaging. In extreme cases, invasive tests such as a liver biopsy may be necessary to check the extent of liver damage and inform the right course of treatment.
There are different types of liver shunts. Doctors prescribe treatment on a case-by-case basis, depending on the location, severity, and type of hepatic shunt. Ideally, closing the shunt should solve the problem, but the surgeon must ensure that closing the bypass vein won't cause more liver damage.
If there's an underlying problem, such as liver or heart damage, the doctor may need to address it first. This can relieve or reduce portal hypertension and encourages blood flow through the liver while minimizing the chances of the shunt reoccurring or developing complications.
Extrahepatic shunts rarely disappear on their own. One way of treating them is with a minimally invasive procedure, such as interventional radiology. In this type of procedure, x-rays and scanning technology guide the insertion of objects like small tubes inside the body.
Other methods to seal off a shunt include inserting embolization coils, vascular plugs, balloons, or chemicals to induce a blockage (embolism).
However, permanently closing off large shunts can cause portal blood pressure to increase dangerously. In these cases, doctors will conduct tests, such as occlusion tests and biopsies, to determine how the liver will react. They can also reduce shunt flow gradually before blocking it completely, giving the liver time to react.
In severe cases, surgery is the best option for hepatic shunts. That includes liver resectioning (cutting a piece of the liver away) and complete liver transplantation.
Surgical treatment of the liver shunt depends on the position and severity of the shunt. Minimally invasive procedures, such as inserting vascular plugs and coils, have the lowest risk. Liver resectioning and transplantation are major procedures, but both are often successful and safe. Shunt surgery is safe, effective, and long-lasting for people with cirrhosis and bleeding.
As liver shunt issues progress, you may experience various complications. The most common are hepatic encephalopathy, bleeding, blood clots, and liver failure.
Liver shunt in humans occurs when blood from the gastrointestinal tract drains directly into a systemic vein and back to the heart, bypassing the liver’s purification stage. This bypass occurs when an abnormal connection develops between the portal and a systemic vein.
A liver shunt can cause several complications and symptoms, including hepatic encephalopathy, liver failure, and heart failure. Diagnosis usually relies on imaging technology, particularly Doppler ultrasound, to detect blood flow.
The location and severity of the shunt determine the treatment. Options include blocking the shunt through minimally invasive procedures or liver transplantation.
Portosystemic shunt surgery involves placing a shunt from the portal vein directly into the vena cava. This surgery is usually necessary to relieve the blood pressure in the portal vein when liver complications cause severe portal hypertension.
After a surgical procedure to treat a portosystemic shunt, the doctor will want to keep you in for a while to observe possible complications. In particular, they will want to monitor portal vein pressure and blood flow through the liver to check if the procedure was successful.