Sinusoidal obstruction syndrome of the liver is blockage of the very small (microscopic) veins in the liver.
Fluid tends to accumulate in the abdomen, the spleen may enlarge, and severe bleeding may occur in the esophagus.
The skin and whites of the eyes may turn yellow, and the abdomen may enlarge.
Doctors base the diagnosis on symptoms and results of Doppler ultrasonography.
If possible, the cause is corrected or eliminated, and symptoms are treated.
(See also Overview of Blood Vessel Disorders of the Liver.)
Sinusoidal obstruction syndrome is similar to Budd-Chiari syndrome except that blood flow is blocked only in very small blood vessels in the liver rather than in larger ones in the liver or in blood vessels outside the liver. That is, blockages do not affect the large hepatic veins and the inferior vena cava (the large vein that carries blood from the lower parts of the body, including the liver, to the heart).
Sinusoidal obstruction syndrome may occur at any age.
Because flow out of the liver is blocked, blood backs up in the liver. This backup (congestion) then reduces the amount of blood entering the liver. Liver cells are damaged because they do not get enough blood (ischemia). The congestion causes the liver to become engorged and enlarged. The congestion also causes increased pressure in the portal vein (portal hypertension). Portal hypertension can result in dilated, twisted (varicose) veins in the esophagus (esophageal varices). The elevated pressure in the portal vein and the liver congestion lead to fluid accumulating in the abdomen—called ascites. The spleen also tends to enlarge.
Such congestion reduces blood flow into the liver. The resulting liver damage leads eventually to severe scarring (cirrhosis).
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Blood Supply of the Liver
Causes of Sinusoidal Obstruction Syndrome
Common causes include the following:
Ingestion of pyrrolizidine alkaloids, which are found in crotalaria and senecio plants (used in Jamaica to make herbal tea) and in other herbs, such as comfrey (see Medicinal herbs and the liver)
Radiation therapy (used to suppress the immune system before bone marrow or stem cell transplantation)
A reaction after bone marrow or stem cell transplantation (graft-versus-host disease)
In graft-versus-host disease, white blood cells in the transplanted tissue attack the recipient’s tissues. This reaction tends to occur about 3 weeks after transplantation.
Symptoms of Sinusoidal Obstruction Syndrome
Symptoms may begin suddenly. The liver enlarges and becomes tender. The abdomen may swell because of fluid accumulating there. The skin and the whites of the eyes may become yellow—a condition called jaundice.
Varicose veins in the esophagus may rupture and bleed, sometimes profusely, causing people to vomit blood and often go into shock. The blood may pass through the digestive tract, making stools black, tarry, and foul-smelling (called melena). When bleeding is severe, shock ensues. A few people develop liver failure with deterioration of brain function (hepatic encephalopathy), resulting in confusion and coma.
Other people develop cirrhosis over time, usually over months, depending on the cause and repeated exposure to toxic agents.
Diagnosis of Sinusoidal Obstruction Syndrome
A doctor's evaluation
Liver blood tests and blood-clotting tests
Ultrasonography or invasive tests
Doctors suspect sinusoidal obstruction syndrome based on symptoms or blood test results that suggest liver dysfunction, particularly if people have ingested substances or have conditions that may cause the disease (particularly people who have had a bone marrow or stem cell transplant). Blood tests, if they have not already been done, are done to determine how well the liver is functioning and whether it is damaged (liver tests) and to evaluate blood clotting.
Doppler ultrasonography often confirms the diagnosis. Occasionally, invasive tests are necessary. These tests include liver biopsy or measurement of blood pressure in the hepatic veins and portal vein. To measure blood pressure in these veins, doctors insert a catheter into a vein in the neck (jugular vein) and thread it to the hepatic veins. A liver biopsy can be done at the same time.
Prognosis of Sinusoidal Obstruction Syndrome
The prognosis depends on how extensive the damage is and whether the condition causing it reoccurs or continues—for example, when people continue to drink senecio tea.
Overall, about one fourth of people with sinusoidal obstruction syndrome die of liver failure.
When the cause is graft-versus-host disease after bone marrow or stem cell transplantation, sinusoidal obstruction syndrome often resolves on its own within a few weeks. Increasing the dose of drugs used to suppress the immune system can also cause graft-versus-host disease to resolve. However, some of these people die of severe liver failure.
If the cause is an ingested substance, stopping its use helps prevent further liver damage.
Treatment of Sinusoidal Obstruction Syndrome
Treatment of cause
Treatment of problems resulting from blocked vessels
There is no specific treatment for the blockage. If possible, the cause should be eliminated or treated. For example, if people are consuming a substance (such as an herbal tea) or taking a drug that can damage the liver, it should be stopped.
Ursodeoxycholic acid helps prevent sinusoidal obstruction syndrome from developing after bone marrow or stem cell transplantation
Problems resulting from the blocked vessels are treated. For example, a low-salt (low-sodium) diet and diuretics help keep fluid from accumulating in the abdomen.
If portal hypertension develops, doctors sometimes try to create an alternate route for blood flow using a procedure called transjugular intrahepatic portal-systemic shunting (TIPS). However, it is unclear whether the procedure is effective.
Liver transplantation may be necessary in rare cases.
