What is Portal Vein Obstruction?
Portal vein obstruction is a health complication often linked to certain metabolic and autoimmune diseases. It usually happens due to a blood clot in the portal vein, which is a major vein supplying blood to the liver. However, it can also occur because of cancerous growths. Given the wide variety of diseases that can cause portal vein obstruction, it’s crucial to understand the common causes, how these diseases affect the body, and relevant treatment options to help patients suffering from this condition.
Most cases of portal vein obstruction are due to a condition called portal vein thrombosis, which is essentially a blood clot in the portal vein. Some cases are related to cancer. This summary will mainly focus on portal vein obstruction caused by portal vein thrombosis, not the ones caused by cancerous growths.
What Causes Portal Vein Obstruction?
The causes of portal vein thrombosis, or a blood clot in a major vein in the liver, can be grouped into two categories: inherited and acquired.
Inherited causes are conditions that you are born with. These include:
* Factor V Leiden mutation, a blood clotting disorder.
* Prothrombin gene mutation, another blood clotting disorder.
* Anti-thrombin III deficiency, when your body lacks a protein that prevents excessive clotting.
* Protein C and S deficiency, when your body lacks other proteins that keep blood clotting in check.
Acquired causes are conditions that develop during your lifetime. These include:
* Lupus anticoagulant syndrome, an immune disorder that increases the risk of blood clots.
* Liver disease.
* Medical procedures or treatments.
* Disseminated intravascular coagulation, a condition where blood clots form throughout the body’s small blood vessels.
* Burns.
* Sepsis, a severe body-wide infection.
* Cancer.
* Disorders of the bone marrow that affect blood cell production.
* Conditions related to childbirth.
* Oral contraceptives.
* Inflammatory states, or conditions that cause your body’s immune system to overreact.
Uncommon causes related to medical procedures can include bariatric surgery for weight loss, radiofrequency ablation for liver cancer, or fine-needle aspiration of pancreatic cancer.
In children, an infection in the abdomen is the most common cause of this blood clot in the liver. A common cause is also the placement of a tube into the belly button in newborns. Other causes can be abnormalities in the vein system of the liver that a child is born with.
In adults, most cases are caused by cirrhosis, or liver scarring. This is followed by cancers. Tumors can squish or grow into the vein or make the blood more likely to clot, leading to portal vein thrombosis. About 10% of cases occur for unknown reasons.
Risk Factors and Frequency for Portal Vein Obstruction
Portal vein occlusion, a health condition affecting the liver, has different rates of occurrence depending on certain health factors and population groups. For instance, it has been seen to affect between 1.6% and 15.8% of individuals with liver conditions such as cirrhosis or portal hypertension. There’s a higher rate of portal vein occlusion in individuals where the liver cirrhosis is specifically caused by alcohol misuse or Hepatitis B infection. However, for those with a milder form of liver cirrhosis, the rates can be as low as 1%, while it can reach up to 25% in patients waiting for a liver transplant. This high rate in liver transplant patients can be due to severely progressed liver disease, reduced mobility caused by severe fluid buildup in the abdomen (ascites), and an unusually high imbalance in blood clotting factors.
Signs and Symptoms of Portal Vein Obstruction
Portal vein thrombosis (PVT) often results in conditions linked to high blood pressure in the portal vein. The way this health issue presents can vary a lot from patient to patient, depending on the root cause. Some common signs include:
- Abdominal pain (found in 91% of cases)
- Fever (found in 53% of cases)
- Ascites, or a buildup of fluid in the abdomen (found in 38% of cases)
Depending on how serious the disease is, around 75 to 100% of patients will also have an enlarged spleen. For those patients where liver cirrhosis is triggering the trouble, further signs might include spiderlike blood vessels on the skin and red palms. Over time, complications like varicose veins around the belly button, hemorrhoids, or bleeding from swollen veins in the esophagus might occur. Ascites is also not uncommon in patients with a blockage in the portal vein.
If cancer is the primary cause of the PVT, whether from a blood clot or from cancer invading the portal vein, obvious symptoms of the cancer could be present. For example, patients with pancreatic cancer often feel extremely tired and have a yellow tinge to their skin and eyes (jaundice). Jaundice is also common in liver cancer and bile duct cancer, and it often comes along with itching.
Treatment decisions for PVT depend on whether the PVT is a new (acute) or old (chronic) problem. Chronic PVT limits the treatment options and might benefit more from either surgery to create a new pathway for blood flow or approaches that aim to improve the quality of life without curing the disease. The reasoning behind this is:
- Extensive duration blood clots are less likely to respond to attempts to break them up, either mechanically or with medicine.
- There’s a lesser chance of restoring normal blood flow if the vein scars from the blood clot and/or if new veins have formed around it.
- Performing a technique called a transjugular intrahepatic portosystemic shunt, or TIPS, might be less successful if a blood clot is making it harder to see the portal vein and more difficult to navigate the anatomy.
Physicians consider a PVT to be ‘chronic’ if the blood clot has been present for at least 4 weeks based on imaging or a consistent symptom history or if there are visible collateral veins on imaging. Some medical centers might not offer TIPS to patients with chronic PVT, and some places also do not offer this procedure for mild PVT, such as when the portal vein is estimated to be blocked less than 25%.
Testing for Portal Vein Obstruction
When doctors suspect that there might be a blockage in your portal vein (the main vein that carries blood from your digestive organs to your liver), they’ll use a variety of methods to figure out if this is really the case. The first thing they’re likely to do is perform a Doppler ultrasound, a simple, non-invasive test that can show how blood is flowing in your veins. Sometimes, they may use a special, “contrast-enhanced” ultrasound, which can give them a better look at the possible obstruction.
At the same time, your doctor might run a number of blood tests, including a liver functioning test to see if there’s any disease affecting your liver. Plus, they’ll probably want to test for a number of factors in your blood that could make it more likely for you to have a blood clot – these include things like antiphospholipid syndrome, and testing the levels of protein C, S, antithrombin III, and something called factor V Leiden mutation.
There’s a specific procedure, known as a TIPS formation, that can help improve the blood flow in your portal vein. But it can be risky, and the older or sicker the person, the higher the chance that it could lead to death. So, many hospitals won’t offer this procedure to people who fall above a certain level of health risk (measured using scores called MELD and Child-Pugh).
Besides ultrasound, your doctor may use CT and MRI scans for more detailed information. These imaging techniques can reveal the extent of any blood clot, signs of damage to your intestines, and the health of organs near the portal vein. MRI scans are particularly good at spotting portal vein blood clots with almost perfect accuracy. They’re also very useful for tracking any cancers that involve the portal vein, and checking up on you after you’ve undergone treatment.
Lastly, a procedure known as endoscopy (which involves running a flexible tube with a camera down your throat to see your digestive system) can be very helpful. This is particularly the case if you’re showing signs of bleeding in your stomach or problems like gastritis. It can also spot swollen veins in your esophagus, which are fairly common in people with chronic portal vein blockages. If these swollen veins are caught quickly, they can be treated with cautery or clips, thereby preventing a potentially serious bleeding episode.
Treatment Options for Portal Vein Obstruction
Treating blood clots in patients with cirrhosis, a liver disease, can be tricky because doctors have to balance the use of blood-thinning medicines with the risk of bleeding. Experts recommend that patients with cirrhosis and a specific type of blood clot known as portal vein thrombosis undergo a procedure called endoscopic screening of esophageal varices. If this procedure indicates the presence of abnormal veins, a banding treatment should be done before starting a specific blood thinner known as low molecular weight heparin (LMWH).
Choosing the right blood thinner can be challenging, as each one has unique benefits and risks. Cirrhosis patients have a naturally high INR value, a measurement of how fast your blood clots. This can make it difficult to monitor the effects of warfarin, a common blood thinner. Despite these challenges, LMWH and vitamin K antagonists, another group of blood thinners, have been used successfully. Current guidelines suggest treating acute portal vein thrombosis for at least 3 months with LMWH, then switching to an oral blood thinner after the patient’s condition has stabilized. One study has shown successful outcomes in up to 60% of cirrhosis patients treated early with LMWH or vitamin K antagonists.
The use of vitamin K antagonists, such as warfarin, has been studied, but no definitive perfect INR value has been established at this time. Another form of blood thinner, LMWH, which does not require monitoring, might be the best choice for some patients.
There’s a risk of the blood clot coming back even after successful treatment. Data from different studies note a recurrence rate between 27-38%.
Some newer blood thinners, known as direct oral anticoagulants (DOACs), have generated interest but currently lack sufficient research evidence to be widely recommended.
If the blood clot is so large that it blocks the view of important structures, making a procedure called TIPS (transjugular intrahepatic portosystemic shunt insertion) likely to fail, the clot should be treated with blood thinners first, if possible.
If the blood clot is caused by local invasion, treating the underlying cancer might be helpful. In patients with blockages due to pancreatic cancer, chemotherapy has led to treatment success and improved survival.
Non-surgical procedures can be used to treat some forms of portal vein thrombosis. However, precise guidelines handing down these treatments do not exist, nor have any of these procedures been proven more beneficial over medical therapy in specific groups of patients.
If a patient with portal vein thrombosis can’t have blood thinners and does not have serious symptoms or anatomical consequences of high pressure in the portal vein, then a procedure known as transhepatic thrombectomy can be considered. This procedure involves the insertion of a device through the abdominal wall into the liver to break down the clot. There are potential dangers, and this use is not approved by the FDA.
When severe symptoms of portal vein hypertension are evident, a procedure called TIPS can be a preferred choice to treat both the blood clot and other associated problems at the same time. From one study, partial and complete elimination of the clot were found in 57% and 30% of patients, respectively.
However, the TIPS procedure doesn’t improve survival in patients with portal vein thrombosis. With a considerable risk for complications, including the potential for worsening liver-related brain dysfunction (known as hepatic encephalopathy), the risks may surpass the benefits of this treatment. Long-term monitoring is also required.
Other surgical techniques, like shunt surgery and the Sugiura procedure, may also be utilized in cases of life-threatening bleeding due to portal vein blockages. However, these should only be considered under specific circumstances due to their potentially significant risks.
Shunt surgery’s role isn’t agreed upon, and endoscopic treatment and certain beta-blockers like propranolol are recommended as first-line therapies in patients with recurrent bleeding. If shunt surgery is done, a specific type called a distal splenorenal shunt is preferred. In patients with cirrhosis, the chance of patient death after shunt surgery is very high.
Finally, liver transplant is an option for a tiny proportion of patients, but it can have serious complications.
What else can Portal Vein Obstruction be?
Portal vein obstruction is usually spotted through medical imaging instead of patient symptoms, so it’s often not suspected unless there’s enough clear evidence. However, it can be mistaken for other conditions because they tend to share similar symptoms or causes. Here are some conditions that should be checked for:
- Primary biliary cirrhosis (a liver disease)
- Arsenic poisoning
- Budd-Chiari syndrome (a rare liver disorder)
- Cirrhosis (scarring of the liver)
- Sarcoidosis (an inflammatory disease that can affect multiple organs)
- Schistosomiasis (parasitic infection)
What to expect with Portal Vein Obstruction
The overall outlook for survival is very good, with a 10-year death rate of about 25% and an overall death rate of around 10%. If the patient has liver scarring (cirrhosis) or cancer, their outlook is generally not as good, and much depends on the seriousness of their underlying condition. However, there are also other possible complications such as esophageal varices; these are enlarged veins in the esophagus, which can be life-threatening. On the bright side, children usually have a better outlook as, in their cases, the cause of the problem is rarely cancer or advanced liver disease.
Possible Complications When Diagnosed with Portal Vein Obstruction
If the portal vein gets blocked, it can lead to several complications:
- Portal Hypertension: This can show up in several ways, including ascites (a buildup of fluid in the abdomen), variceal hemorrhage (bleeding caused by swollen veins in the esophagus and stomach), or hypersplenism (an overactive spleen).
- Mesenteric Infarction: This is most commonly seen in cases of sudden portal vein clotting, which leads to a blockage of blood flow from the mesenteries (the folds of tissue in the abdomen that connect the intestines to the wall of the stomach).
- Worsening Liver Function: In patients that already have liver scarring, a blocked portal vein can make their liver function worse.
- Acute Pylephlebitis: This is an infection of the portal vein, which can occur if there’s an ongoing infection somewhere in the abdomen (like appendicitis or diverticulitis).
Preventing Portal Vein Obstruction
A study was conducted by Villa and others to determine whether enoxaparin, a medication, is safe and capable of preventing portal vein thrombosis (PVT) in patients with severe cirrhosis. Portal vein thrombosis is a blood clot that can occur in the liver’s main vein, and cirrhosis is a late stage of scarring of the liver. This study was small and controlled, and patients were observed for 12 months.
According to the results, enoxaparin was safe and effective at preventing PVT in patients with severe cirrhosis. The medication also seemed to delay the worsening of liver disease and improved survival rates. However, these results need to be verified by larger, more extensive trials carried out at multiple medical centers.
Patients who are at a high risk of developing portal vein thrombosis need to be informed about these potential complications. It’s important for these patients to report any new symptoms to their doctor, which could lead to early diagnosis and treatment.
