Modified diagnostic criteria, grading classification and newly elucidated pathophysiology of hepatic SOS/VOD after haematopoietic cell transplantation

Summary Sinusoidal obstruction syndrome (SOS), previously known as hepatic veno‐occlusive disease (VOD), remains a multi‐organ system complication following haematopoietic cell transplantation (HCT). When SOS/VOD is accompanied by multi‐organ dysfunction, overall mortality rates remain >80%. However, the definitions related to the diagnosis and grading of SOS/VOD after HCT are almost 25 years old and require new and contemporary modifications. Importantly, the pathophysiology of SOS/VOD, including the contribution of dysregulated inflammatory and coagulation cascades as well as the critical importance of liver and vascular derived endothelial dysfunction, have been elucidated. Here we summarise new information on pathogenesis of SOS/VOD; identify modifiable and unmodifiable risk factors for disease development; propose novel, contemporary and panel opinion‐based diagnostic criteria and an innovative organ‐based method of SOS/VOD grading classification; and review current approaches for prophylaxis and treatment of SOS/VOD. This review will hopefully illuminate pathways responsible for drug‐induced liver injury and manifestations of disease, sharpen awareness of risk for disease development and enhance the timely and correct diagnosis of SOS/VOD post‐HCT.