Sinusoidal obstruction syndrome (SOS) is a life-threatening complication of hematopoietic stem cell transplantation (HSCT), particularly in patients with a high HokUS-10 score after starting treatment. Tolvaptan sodium phosphate (TSP) is a novel intravenous aquaretic agent used to treat refractory fluid retention in congestive heart failure (CHF). Here, we report the successful treatment of severe post-HSCT SOS with refractory fluid retention and CHF using TSP plus defibrotide. A 22-year-old man with relapsed acute lymphoblastic leukemia underwent unrelated peripheral blood stem cell transplantation and developed SOS on day 13. Despite defibrotide therapy and standard management, fluid retention rapidly progressed, resulting in an 18.3% increase in body weight on day 21 and a high HokUS-10 score (10/13 points). TSP (16 mg) administered to treat the CHF immediately induced adequate urine output. Continued TSP treatment (8 mg/day) resulted in sustained diuresis and a return to baseline body weight on day 33. The only significant adverse event observed during the 5 weeks of TSP treatment was transient hypernatremia (148 mEq/L). Defibrotide was discontinued on day 72 because the HokUS-10 score had decreased to 1 point. Our experience suggests the utility of TSP in controlling refractory fluid retention due to post-HSCT SOS.
