Sinusoidal obstruction syndrome

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Sinusoidal obstruction syndrome (SOS), previously known as hepatic veno-occlusive disease (VOD), is a condition arising from occlusion of hepatic venules.

Clinical presentation

right upper quadrant pain
painful hepatomegaly
ascites
abnormal liver function tests

Pathology

Toxic injury to liver sinusoids causes sloughing of endothelial cells that embolize to hepatic venules and cause eventual fibrosis of the venules. This results in hepatic congestion (similar to Budd-Chiari syndrome) and post-sinusoidal portal hypertension.

Etiology

bone marrow transplantation
chemotherapy, includes systemic neo-adjuvant chemotherapy in metastatic colorectal cancer, particularly the use of oxaliplatin
pyrrolizidine alkaloids (Jamaican bush tea)

Radiographic features

Ultrasound

The imaging modality of choice, which may show:

hepatomegaly
portal vein abnormalities:
- portal vein dilatation
- portal venous pulsatility
- hepatofugal portal venous flow
elevated hepatic artery resistive index (> 0.8)
loss of triphasic hepatic venous flow
gallbladder wall thickening (> 6-8 mm)
ascites

CT

hepatomegaly
nutmeg liver
portal vein dilatation
ascites

MRI

Recent MRI studies with hepatocyte-specific contrast agent show a diffuse hypointense reticular pattern on post-contrast T1 delayed hepatobiliary phase as a highly specific sign for the diagnosis.

Treatment and prognosis

There is no standard treatment regimen but options include:

anticoagulation
vasodilators
supportive care

Preoperative planning for hepatic metastasectomy should include exclusion of SOS after the use of chemotherapy as there is an increased risk of postoperative liver failure.

Approximately half resolve but high mortality in severe cases (up to 90%).