Thrombosis secondary to renal closed abdominal trauma is a rare event, most of the time it is clinically silent. We report here our experience. MATERIALS AND METHODS. This is the case of a boy came to our observation after a road trauma with motorbike fall-out. The boy arrived in ED for head injury. The patient, stable for haemodynamics, had lacerated and contused injuries at pelvis and right buttock level. He underwent chest x-rays, brain CT and neurosurgery examination: all resulted negative. There was no macrohematuria, nor lumbar pain. Objectively abdomen was treatable. The patient was referred to temporary observation for 12 hours when he was asked to undergo abdomen ultrasound, which showed no documented lesions except for fluid collection at the pelvic level. To rule out all doubts, the patient had an abdominal CT scan, which showed a silent left kidney with suspected thrombosis at left renal level. The patient was sent to our attention after 15 hours: we decided to perform immediately selective arteriography with thrombus lysis. The arteriography documented a massive thrombosis. The thrombus lysis was impossible to be performed. To maintain the perfect functionality of the contralateral kidney we decided not to proceed further, but to perform only left nephrectomy. During surgery mesocolon laceration occurred, so the patient underwent also colic resection. DISCUSSION. Thrombosis secondary to a closed renal abdominal trauma is an uncommon event, with little clinical expression. It is the consequence of an injury. Deceleration produces arterial dissection, which alters the blood flow to the kidney, which is then twisted and complicated with renal thrombosis. Quite common is the association with diaphragmatic rupture or urethral detachment. The alterations of renal parenchyma in the early hours are detectable only through CT scan, which represents the method of election, and which can highlight a functionally silent kidney. CONCLUSIONS. Renal thrombosis requires that diagnosis is done within the first 12 hours; a rapid revascularization should be promptly attempted.