Early-onset severe sinusoidal obstruction syndrome following adjuvant CAPOX: clinicoradiological diagnosis and favourable outcome after treatment with defibrotide.

Sinusoidal obstruction syndrome (SOS) is an uncommon hepatic vascular complication classically associated with haematopoietic stem cell transplantation, although it may also occur following oxaliplatin-based chemotherapy. We report the case of a 52-year-old woman with stage III colon adenocarcinoma treated with adjuvant CAPOX who developed jaundice, ascites, rapid weight gain, thrombocytopenia, and severe liver dysfunction three weeks after completing chemotherapy. After other causes of acute liver injury had been excluded, Doppler ultrasound demonstrated reversal of portal venous flow and signs of portal hypertension consistent with SOS. Given the severity and rapid progression of the condition, treatment with defibrotide was initiated alongside supportive care, resulting in rapid clinical, biochemical, and radiological improvement. This case highlights that SOS may occur early, even after limited exposure to oxaliplatin in the adjuvant setting. Early recognition and assessment with hepatic Doppler ultrasound are essential to establish the diagnosis and initiate prompt treatment.