What is Mesenteric Venous Thrombosis?
Mesenteric venous thrombosis is a condition where a blood clot forms in the superior or inferior mesenteric vein or its branches. These veins are engaged in carrying blood from the intestines to the liver. These clots can occur due to inherited or acquired blood clotting disorders or as a result of conditions that cause inflammation in the body. Damage, slowed blood flow, cancer, infection, injury, and systematic inflammation can all contribute to the development of these clots.
While more than 25% of cases may initially appear to have no clear cause, a thorough examination often reveals an identifiable cause. The clot can start in the smaller veins (vena rectae) or a major vein and may even involve the portal vein, which carries blood from the gastrointestinal tract to the liver. The superior mesenteric vein is involved in more than 90% of these cases, with the inferior mesenteric vein being implicated in only up to 11% of the cases.
Mesenteric venous thrombosis can be an acute (sudden), subacute (slightly delayed), or chronic (long-term) process. These clots account for 5% to 15% of acute cases of mesenteric ischemia (a serious condition where there is inadequate blood supply to the small intestine) and are responsible for 1 in 5000 to 15,000 hospital admissions and 1 in 1000 emergency department visits. Chronic mesenteric venous thrombosis accounts for 20% to 40% of all such cases and is often discovered accidentally. Despite its relative rarity, it can be deadly due to vague symptoms and delay in diagnosis.
The location, speed of development, and size of the clot can affect the patient’s outlook. People with chronic clots may experience complications from high blood pressure in the veins, such as malnutrition and enlarged veins in the esophagus or stomach. Chronic clots can form alternate pathways for blood flow that protect the bowel from ischemic changes (damage from lack of oxygen). However, when a clot forms suddenly, bowel ischemia may occur quickly. This acute ischemia can cause extensive intestinal damage, leading to severe infections, multiple organ failures, and even death.
Treatment for mesenteric venous thrombosis varies, ranging from short-term blood thinners with management of the underlying condition causing inflammation, to prolonged hospital stay and emergency surgery. The goal of the treatment is to protect the organ tissues, stop the clot from expanding, and reduce the chances of it occurring again. Blood thinners are often a crucial part of treatment. Even patients with enlarged veins should be on blood thinners, but those with symptoms from enlarged veins may need to have pressure released from their veins before they can start on blood thinners.
What Causes Mesenteric Venous Thrombosis?
Most people who have a condition called mesenteric venous thrombosis, a blood clot in the veins that carry blood away from the intestines, also tend to have a high risk of forming more clots. This can be due to genetic or acquired causes and may happen alongside trauma, infection, inflammation, or surgery. This condition can also arise from slow blood flow often seen in heart failure or a liver disease called cirrhosis. Conditions that increase the risk of getting clots include cancers, some reactions to heparin (a type of blood-thinning medication), several blood disorders, the presence of specific antibodies, using birth control pills, and pregnancy. Genetic disorders like sickle cell disease, Factor V Leiden, having too many clot-forming proteins, or lacking certain clot-dissolving proteins can also increase this risk.
Patients with a blood clot in a main vein draining the intestines often have another clot in the vein supplying the liver. They’re more likely to have conditions like bowel diseases that cause inflammation, inflammation of the pancreas, bowel pouches (diverticulitis), cancers, and certain kinds of blood disorders. People with cirrhosis are also more likely to have a clot in the liver vein. It’s even seen in about 15% of people waiting for a liver transplant. If there’s a clot in smaller vessels, it’s likely the patient has a condition that makes them prone to getting clots.
While up to 25% of mesenteric vein thrombosis cases may first seem to have no cause, detailed examination usually uncovers the reason. For instance, a genetic change that increases the production of blood cells, known as the JAK2V617F mutation, can help in diagnosing disease before symptoms show up. It can also distinguish whether the clot-forming condition is inherited or a reaction to something. This mutation is found in most patients with polycythemia vera (a blood disorder that makes your body produce too many red blood cells) and in half of those with essential thrombocythemia and myelofibrosis (types of blood disorders). Also, almost half of the cases without obvious blood disorders have this mutation.
Risk Factors and Frequency for Mesenteric Venous Thrombosis
Acute mesenteric venous thrombosis is a condition that results in blockage of blood flow, contributing to between 5% and 15% of all instances of mesenteric ischemia, which is an interruption of the blood supply to the intestines. It is estimated to account for between 1 in 5,000 to 15,000 hospital admissions and 1 in 1,000 emergency department visits. Despite the rarity of the disease, with a rate of 2.7 occurrences per 100,000 people, diagnosis has become more common due to enhanced technology; specifically, computed tomography or CT scans. These scans are now able to identify about 90% of these cases even during assessments for unrelated conditions.
- Mesenteric venous thrombosis accounts for about 5% to 15% of all mesenteric ischemia cases.
- It only accounts for 1 in 5,000 to 15,000 hospital admissions and 1 in 1,000 emergency room visits.
- The estimated incidence rate is 2.7 per 100,000 individuals.
- Computed tomography (CT) scans have significantly increased the detection rate of this condition, identifying about 90% of cases.
- Despite this, the death rate still ranges between 19% and 23%.
- Mesenteric venous thrombosis happens slightly more often in men, typically showing up in individuals aged between 40 and 60.
Signs and Symptoms of Mesenteric Venous Thrombosis
Mesenteric venous thrombosis is a condition where a blood clot forms in one or more of the veins that drain blood from the intestine. How this condition presents can be quite different based on the speed at which it develops and its cause. It can range from an unnoticed condition that is discovered by chance, to a severe illness with symptoms of inflammation in the abdomen and severe infection.
Often, individuals with this condition will experience diffuse abdominal pain, lack of appetite, nausea, and vomiting over several days. The person may also have a history of infections or inflammation. If the patient or their family has a history of blood clots, this could suggest a genetic predisposition to blood clotting disorders. Chronic mesenteric venous thrombosis, which develops over time, may be associated with serious underlying illnesses, such as high blood pressure in the liver.
Physical signs in chronic cases may vary. They can be inconspicuous or show signs of issues like liver cirrhosis and high liver blood pressure. These signs might include spider vein patterns visible on the skin, redness in the palms, bloated veins around the belly button, and signs of bleeding from enlarged veins in the esophagus. The person might also show signs of discomfort, swelling in the abdomen, and fluid accumulation in the belly.
People with acute mesenteric venous thrombosis often have severe pain that doesn’t match the physical signs, accompanied by nausea, vomiting, and diarrhea. If fever is present, it may suggest there is an infection, or an issue in the abdominal area like appendicitis or inflammation of the pouches in the wall of the colon. The patient may show signs of dehydration and unstable vital signs.
Those with subacute mesenteric venous thrombosis, which develops over a longer period, usually suffer from symptoms over days to weeks, averaging 6 to 14 days. In these patients, it’s common to see abdominal swelling. These people tend to have mild to moderate, widespread pain. Excess fluid in the abdominal cavity may also be noticed.
Testing for Mesenteric Venous Thrombosis
Doctors use various imaging techniques to confirm if a patient has mesenteric venous thrombosis, which is a blood clot in the veins of one’s bowel. The most effective tool for identifying this condition is an abdominopelvic CT scan with a dye injection, which can identify it in around 90% of cases. Another technique called plain abdominal radiographs can indicate abnormalities in 50% to 75% of cases, but these signs, such as a distended bowel, are not specifically unique to the condition. Other imaging methods like MRI, angiography (a technique to visualize blood vessels), and abdominal Doppler ultrasonography (ultrasound to measure blood flow) are used less often because of their lower sensitivity and inability to visualize small veins.
On CT scan images, a venous blood clot appears as a focused radiolucent (area appearing dark on the image). Signs of tissue death due to insufficient blood supply (ischemia) include a bowel wall that is thicker than 3mm, a thickened tissue that supplies blood to the intestines (mesentery), and fluid surrounding this area. If bowel tissue death is advanced, the bowel wall may be thicker than 10 mm. The presence of gas in the portal vein and air bubbles in the bowel wall suggest necrotic (dead) bowel and free air inside the abdomen can indicate a bowel rupture.
If a mesenteric venous thrombosis is detected on a CT scan, further evaluation of the bile duct system and the extent of pressure within the portal vein can be performed using magnetic resonance cholangiopancreatography (MRCP – a type of MRI that focuses on the bile ducts) or endoscopic retrograde cholangiopancreatography (ERCP – a procedure that combines endoscopy and X-ray to diagnose diseases of the pancreas and bile ducts). However, ERCP can risk bleeding from catheter injury. An esophagogastroduodenoscopy (EGD – a test that examines the lining of the esophagus, stomach, and top of the small intestine) can be useful in evaluating esophageal and stomach varices, which are abnormal, dilated veins.
While routine lab tests can’t specifically confirm mesenteric venous thrombosis, they can provide helpful clinical information. Doctors might order a complete blood count, comprehensive metabolic panel, coagulation tests to measure how your blood clots, and tests to screen for thrombophilia (an increased tendency to develop blood clots). An elevated lactate level can signify late-stage tissue death due to lack of blood supply (ischemia), and high amylase (a digestive enzyme) levels might indicate bowel ischemia or suggest pancreatitis (inflammation of the pancreas). Blood cultures are essential for patients with fevers and hemodynamic instability (a state of abnormal blood flow). Patients with involvement of the portal vein or sepsis will have elevated liver enzymes.
Treatment Options for Mesenteric Venous Thrombosis
The treatment for acute and subacute mesenteric venous thromboses, which are blood clots in the veins of the small intestine, varies depending on the severity of the condition and can range from resting the bowel and replacing fluids, and providing blood-thinning medication, to more extensive surgery where a part of the bowel is removed. The aim is to stop the death of bowel tissue, stop the blood clot from growing larger, and limit the chances of it happening again. If you are stable, the doctor may suggest non-surgical treatment with bowel rest, replacing body salts, and blood-thinning medication. If you are feeling sick, medication that wipes out a wide variety of bacteria may be helpful to treat the inflammation of the vein wall or bacteria that have moved from the gut.
If the blood clot is large or your condition worsens, intervention may be required. In the past, the only urgent option was open surgery but now interventional radiology (IR) can offer more targeted therapies. IR is a special way of treating diseases using imaging technologies. It can help dissolve clots through a method called catheter-directed thrombolysis, can directly remove clots (thrombectomy), and can deliver drugs that widen blood vessels or dissolve clots. These therapies can often improve symptoms and lower the need for surgery to remove a part of the bowel.
During an IR procedure, the doctor gets access to your veins through a long, thin tube (catheter) inserted through your skin, using the jugular vein in your neck or through your liver. They use a special kind of catheter to cross the clot. If they use a clot-dissolving drug called tPA, they give an initial dose then continue to infuse the drug at a lower dose. They can also use other medicines like Heparin, a blood thinner, or urokinase, another clot-dissolving drug. After the procedure, they check your veins. However, this method can’t be used if you have a brain bleed, have a history of strokes, have diseases that affect the brain and nerves, have recently had surgery, have experienced trauma, or if your bowel tissue has started to die.
If you become severely ill due to dead bowel tissue or if a part of your digestive system pops a hole, then open surgery may be necessary. Here, the surgeon identifies the clot area and cuts out the affected section of bowel. The goal is to preserve as much of your bowel as possible whilst removing dead tissue, and usually, about 50 to 60 cm of bowel is removed.
In terms of medication, anticoagulation or blood-thinning medications, are the foundation of treatment. If the chance of needing an invasive procedure or if kidney function is poor, Heparin, a kind of anticoagulant is usually given first. Once you are stable, the doctor may switch to an oral medication like warfarin or a direct oral anticoagulant (DOAC). If your blood clot was caused by a reversible condition, you may need to keep taking the blood thinner for 6 months. But if you have a condition that increases your chances of developing blood clots, you may need to take the blood thinner for a longer period, sometimes even for life.
Even with the risks, blood-thinning medications are still very important. That’s because they can reopen the vein, and are especially important even if you have other health conditions like cirrhosis or high blood pressure in the veins of your liver. For these patients, 50% see their vein reopen when they are given anticoagulants. But without blood thinners, the vein does not reopen.
Patients with increased pressure in the veins of their liver may need an intervention like a transjugular intrahepatic portosystemic shunt (TIPS) to prevent bleeding before taking anticoagulant medication. This procedure uses a tube to connect the portal vein (which carries blood from your digestive organs to your liver) to the hepatic vein (which carries blood from the liver to the heart) and thus, reduces pressure. If you have liver scarring from long-standing liver disease, then a shunt can be created between the left portal vein and the superior mesenteric vein. Lastly, some patients may need a stent for bile ducts that have become narrow as a result of long-standing portal vein thrombosis. In rare cases, a surgical procedure may be necessary to bypass constricted bile ducts.
What else can Mesenteric Venous Thrombosis be?
Identifying mesenteric venous thrombosis (a blood clot in a major vein that carries blood to your intestine) can be challenging, as its symptoms can be unclear and vary from mild to severe. Based on a physical examination and lab tests alone, several conditions such as intestinal disease, heart attack, and aortic dissection (a serious condition in which the inner layer of the aorta splits) could be considered by the doctors.
It’s also really important to know the difference between mesenteric venous thrombosis and mesenteric arterial thrombosis (a clot in an artery that supplies blood to your intestine), because they have different causes and treatment methods. Mesenteric venous thrombosis could also occur alongside an infection or inflammation.
What to expect with Mesenteric Venous Thrombosis
Mortality, or the risk of death, has generally decreased thanks to earlier diagnosis and treatment. However, mesenteric venous thrombosis (a blood clot in a major vein that drains blood from your intestines), is still a very serious condition. A delay in diagnosing it can lead to worse outcomes. The main causes of death for people with mesenteric venous thrombosis are sepsis (a serious infection), pulmonary emboli (a blood clot in the lungs), and complications from additional blood clots.
Factors such as the patient’s age, their other health conditions, the time it takes to diagnose the thrombosis, and the success of treatment all affect the outcome.
Acute mesenteric venous thrombosis – or a sudden blood clot – has a 30-day mortality rate of up to 32%. A prompt diagnosis can lower this to less than 10%. However, if diagnosis is delayed, the mortality rate can be as high as 60%. If treatment is further delayed beyond 24 hours after the symptoms start, mortality can range between 80% and 100%.
However, for patients with chronic mesenteric venous thrombosis – or a long-standing blood clot – survival rates can reach up to 82% over five years. In cases of chronic thrombosis, the overall outlook is based on the severity of their other health conditions.
Possible Complications When Diagnosed with Mesenteric Venous Thrombosis
Mesenteric venous thrombosis is a blood clot formed in the veins of the intestine. This can result in complications that arise from the clot itself, the treatments required to deal with the clot, and the underlying condition that caused the clot. One of these potential complications is the return of the clot, usually within the first 30 days. This recurrence rate drops to 0-3% for those who receive anticoagulation treatment. However, if the clot does return or extend, it can cause bowel tissue death, severe infection, and even death. If part of the intestine needs to be removed because of the clot, patients may have to rely on total parenteral nutrition i.e., receiving all nutrients through a vein, for the rest of their lives.
Other complications can arise from a treatment known as catheter-directed thrombolysis. These complications can include excessive bleeding, fever, formation of a bruise or hematoma, pain, and infection. Increased bleeding risk can be seen with thrombolytic therapy administered through the liver or through a surgical access point in the bowel. The risk of bleeding due to anticoagulation is usually less than 10% and typically occurs within the gastrointestinal system. For patients with varices, or enlarged veins, the risk of bleeding is higher and they may need to be treated with beta blockers or another definitive treatment for enlarged veins.
Long-term clotting can lead to further complications such as blockages in the bile ducts, gallstones, and repeated inflammation of the bile ducts. These often require major reconstructive surgery. Blood disorders that cause thrombosis in some people can progress to leukemia and myelodysplasia. Patients with chronic thrombosis can experience symptoms such as consistent tiredness, bone pain, itching, weight loss, and bleeding due to platelet dysfunction.
Here are the potential complications:
- Return or extension of the clot
- Bowel tissue death
- Severe infection
- Potential death
- Need for total parenteral nutrition
- Excessive bleeding
- Fever
- Formation of a bruise or hematoma
- Pain and infection
- Bleeding within the gastrointestinal system
- Blockages in the bile ducts, gallstones and repeated inflammation of the bile ducts
- Leukemia and myelodysplasia
- Consistent tiredness, bone pain, itching, weight loss, and bleeding due to platelet dysfunction
Recovery from Mesenteric Venous Thrombosis
The level of care needed after surgery and during recovery depends on the cause and seriousness of the mesenteric venous thrombosis, a blood clot in the major veins that drain blood from the intestine. People who develop failure of multiple body systems that need intensive care will have a lengthy recovery journey. They might also face challenges such as more blood clots forming, blood clots travelling to the lungs, bleeding in the gut, needing a machine to help them breathe for a prolonged period, and only being able to get nutrition through injections.
Patients who’ve had surgery may require more procedures, possibly rebuilding part of the intestines, and the wound on their stomach may take time to fully close. Some patients will need to be consistently monitored in terms of nutrition, and even require additional nutritional support. If the cause of the blood clot was unknown or due a chronic illness, they will need to take medicine to prevent blood clots for the rest of their life.
Preventing Mesenteric Venous Thrombosis
We need to identify patients who might have a higher risk of developing a condition called mesenteric venous thrombosis. Often, these are people who either have a history of blood clots in their family or personally. It can also be those with long-term (chronic) inflammatory conditions or a known condition called portal hypertension and cirrhosis. For clarity, mesenteric venous thrombosis is a blood clot in the veins that drain blood from the intestine. Portal hypertension is high blood pressure in the veins that bring blood to the liver, and cirrhosis is a severe liver condition.
It’s crucial for these individuals to know that if they have severe or constant (unrelenting) abdominal pain, they should seek immediate medical help. Some patients with a higher risk might benefit from preventive (prophylactic) treatment with drugs that prevent blood clots (anticoagulants).
