According to the 2024 European Association of Urology guidelines, renal stones is one of the delayed complications of renal trauma. We report a case without prior history of renal stones whom developed a renal hematoma after traffic collision. Months later, a renal stone formed at the hematoma site. Imaging and pathological evidence suggest that the renal stone was formed from the initial hematoma. Based on this novel finding, we review current renal trauma management strategies and propose two potential mechanisms linking renal hematoma to stone formation.

A 65-year-old female without previous history of urinary tract related conditions. Her vital sign was unstable with hypovolemic shock at our emergency department after a motor vehicle accident. Abdominal computed tomography (CT) revealed a left-sided grade IV renal laceration with perirenal hematoma. Transarterial embolization was then performed for hemostasis, and the patient was admitted to the surgical intensive care unit for close monitoring. Due to relatively stable condition, she was transferred to ordinary ward three days later and discharged on the fifth day of admission. Subsequent ultrasound performed revealed decreased-size perirenal hematoma, accompanied by grade 1-2 hydronephrosis. However, about two months after discharging, the patient came to our emergency department again because of fever for two days. Abdominal CT revealed a left upper third ureteral stone with hydroureteronephrosis and a left renal pelvic stone. The patient admitted for infection control first, then received left ureteroscopic lithotripsy for the left ureteropelvic junction stone as well as left retrograde intrarenal surgery for left lower calyx renal stone. The stone appeared to be composed of blood clot-like tissue in the core region under ureteroscopy. The entire procedure was completed without complications. Subsequent follow-up in the outpatient department showed no recurrence of stones.

When it comes to the management of blunt renal trauma, the key points include assessing hemodynamic stability, determining the extent of injury by abdominal CT imaging, and evaluating severity based on The American Association for the Surgery of Trauma (AAST) grading scale. Additionally, continuous monitoring of complications, including both short-term and long-term complications, is also necessary. Besides, based on our case, one of the hypotheses of renal hematoma followed by renal stones is that hematoma acts as a foreign body, providing a surface for mineral deposition. The other hypothesis suggests that the renal hematoma obstructed the urinary system, leading to urine stasis and subsequently promoting renal stone formation.

This case highlights the need for long-term follow-up in renal trauma patients, as hematoma-related complications may lead to renal stones.