Sinusoidal obstruction syndrome

Objectives: To provide an updated version of the Sociedade Brasileira de Terapia Celular e Transplante de Medula Óssea (SBTMO) 2021 consensus on sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), incorporating recent evidence regarding pathophysiology, risk stratification, diagnosis, prophylaxis, and treatment following hematopoietic stem cell transplantation (HSCT). Methods: A narrative review of the literature was performed, emphasizing studies and international recommendations published since the 2021 SBTMO consensus. Evidence regarding risk factors, diagnostic criteria, severity classification, biomarkers, imaging modalities, prophylactic strategies, and therapeutic interventions was critically reviewed, with particular focus on the refined European Society for Blood and Marrow Transplantation (EBMT) 2023 diagnostic and severity criteria. Results: Recent evidence supports earlier recognition of SOS through the refined EBMT 2023 criteria, which incorporate probable, clinical, and proven disease categories, dynamic bilirubin assessment, and markers of organ dysfunction, including Sequential Organ Failure Assessment-based severity evaluation. Emerging diagnostic tools, such as liver stiffness measurement and endothelial biomarkers, may improve early detection and risk stratification. Contemporary studies reinforce the benefit of prophylactic ursodeoxycholic acid and defibrotide in selected high-risk patients. Defibrotide remains the standard treatment for moderate to severe SOS, with accumulating real-world evidence demonstrating improved survival when therapy is initiated promptly after diagnosis. Conclusions: This updated SBTMO consensus reflects important advances in the diagnosis and management of SOS after HSCT. The integration of refined EBMT diagnostic criteria, emerging biomarkers, novel imaging techniques, and contemporary evidence on prophylaxis and treatment provides a practical framework for earlier diagnosis, improved risk stratification, timely therapeutic intervention, and potentially better clinical outcomes in this life-threatening transplant-related complication.