Background: Wunderlich’s syndrome (WS) is an extremely rare condition, characterised by spontaneous haemorrhage into the subcap sular, perirenal, and retroperitoneal spaces. The most common cause is renal angiomyolipoma. Classic symptoms, such as acute flank pain, flank mass, and hypovolemic shock, known as Lenk’s triad, have limited sensitivity and specificity for detecting WS. High mortality may be related to the difficulties in diagnosis, poor disease recognition, and non‑specific symptoms and signs. Computed tomography (CT) is the method of choice for the diagnosis of WS. Depending on the severity of symptoms, a conservative or invasive approach is reasonable. Methods and results: We report the case of a 58‑year‑old male with multivalvular heart defect, atrial fibrillation, and exacerbation of chronic heart failure complicated with nontraumatic bleeding into the retroperitoneal space. CT revealed a massive (14x11x26 cm) retroperitoneal and perirenal haematoma. The patient was successfully treated with transfusion of red blood cells, fresh frozen plasma, and intravenous fluids. Simultaneously, heart failure treatment was initiated. In view of the chronic and idiopathic charac ter of the haematoma and successful conservative treatment, there was no indication for surgery. Discussion: Several factors might have contributed to the bleeding. First, the patient was receiving anticoagulant treatment to reduce the risk of arterial thromboembolism in atrial fibrillation. Another possible cause is post‑radiation vasculopathy, an adverse effect of previous radiation therapy for malignant granuloma. The third factor which could have contributed to bleeding was the exacerbation of chronic heart failure and pulmonary hypertension.