Sinusoidal Obstruction Syndrome (Veno-Occlusive Disease)

Sinusoidal obstruction syndrome is a rare but serious liver condition. It happens when the small blood vessels inside the liver become blocked and damaged. This condition is also called veno-occlusive disease or VOD.

The blockage occurs in the tiny sinusoids, which are specialized blood vessels in the liver. When these vessels get blocked, blood cannot flow through the liver properly. This causes blood to back up and fluid to leak into liver tissue. The liver swells and stops working as it should.

This condition most often develops after bone marrow transplant or certain types of chemotherapy. The medicines used in these treatments can damage the delicate cells lining the liver's blood vessels. Most cases occur within 3 weeks after transplant or high-dose chemotherapy. Early detection and treatment improve outcomes significantly.

• Sudden weight gain from fluid buildup
• Swelling in the belly and legs
• Pain or tenderness in the upper right abdomen
• Yellowing of the skin or eyes, called jaundice
• Enlarged liver that feels firm when pressed
• Dark urine and pale stools
• Confusion or mental changes from liver dysfunction
• Bleeding or bruising easily
• Fluid in the abdomen, called ascites

Some people have mild symptoms at first that worsen quickly. Others develop severe symptoms within days. Early signs can be easy to miss, especially in patients already dealing with side effects from cancer treatment.

Sinusoidal obstruction syndrome happens when powerful medicines damage the cells lining the liver's blood vessels. High-dose chemotherapy before bone marrow or stem cell transplant is the most common cause. Certain chemotherapy drugs directly injure these delicate vessel linings. Radiation to the liver can also trigger this condition. The damaged cells swell and release substances that cause blood clots to form in the tiny liver vessels.

Risk factors include certain pre-existing liver conditions, previous liver disease, older age, and specific conditioning regimens. People receiving transplants for leukemia or other blood cancers face higher risk. Using multiple chemotherapy drugs together increases the chance of vessel damage. Prior radiation to the abdomen and certain genetic factors also raise risk. Children and adults over 60 have greater vulnerability to this condition.

Doctors diagnose sinusoidal obstruction syndrome using a combination of symptoms, physical exam findings, and blood tests. The diagnosis is often based on clinical criteria that include jaundice, liver enlargement, fluid retention, and weight gain within 3 weeks of transplant or chemotherapy. Blood tests help confirm liver damage and rule out other causes.

Alanine aminotransferase or ALT is a key blood test that shows liver cell injury. ALT levels rise when liver cells are damaged by the blocked blood vessels. Rite Aid offers ALT testing through our flagship panel at Quest Diagnostics locations nationwide. Doctors also check bilirubin levels, which measure how well the liver processes waste. Imaging tests like ultrasound can show blood flow problems in the liver. In some cases, a liver biopsy confirms the diagnosis.

• Defibrotide, a medication that protects blood vessel linings and helps dissolve clots
• Diuretics to reduce fluid buildup in the belly and legs
• Pain management with careful medication selection to avoid liver stress
• Nutritional support and close monitoring of fluid balance
• Reduction or stopping of medications that harm the liver
• Supportive care in intensive care units for severe cases
• Prevention strategies before transplant in high-risk patients
• Avoidance of additional liver-toxic drugs during recovery

Treatment works best when started early. Mild cases may resolve with supportive care alone. Severe cases require specialized treatment with defibrotide and intensive monitoring. Work closely with your transplant team or oncologist if you are at risk for this condition.