Solitary kidney, which has various causes, is a condition in which a person has a single kidney. Congenital causes include renal agenesis and renal dysplasia [1]. The major acquired cause is unilateral nephrectomy for reasons such as renal trauma, disease (e.g., renal cell carcinoma), and donation for kidney transplantation [2]. According to the annual statistics of the Korea Organ Donation Agency, the renal transplantation rate in Korea has been increasing every year and 848 kidney transplants were performed in 2020 [3]. Therefore, as the number of kidney donors increases, solitary-kidney patients are increasing.

A high-grade kidney injury is defined as an American Association for the Surgery of Trauma (AAST) grade IV or V injury. AAST grade IV refers to parenchymal laceration extending through the renal cortex, medulla, and collecting system, and in the vascular case, it is the main renal artery or vein injury with contained hemorrhage. AAST grade V is a state of completely shattered kidney or avulsion of the renal hilum [4]. According to recent protocols, the initial management of renal trauma depends on hemodynamic status rather than the grade of the injury. For hemodynamically stable patients, conservative management, including expectant management or angioembolization, is recommended [5,6]. According to the European Association of Urology, the World Society of Emergency Surgery (WSES) and AAST, surgical management should be considered for hemodynamically unstable patients [4,7]. Unfortunately, surgical management for unstable patients usually ends in unilateral nephrectomy [8]. For patients who have bilateral kidneys, this is not a lethal outcome, but for solitary-kidney patients, it can be a critical problem. Once nephrectomy occurs in patients who have a traumatic high-grade renal injury with solitary kidney, the patient must undergo lifelong dialysis or wait for kidney transplantation. Korea suffers from a shortage of organ donors, and long-term dialysis has the risk of various complications and mortality.

In recent studies, superselective embolization for high-grade renal trauma has been reported to show a high therapeutic success rate for hemostasis and a higher likelihood of kidney preservation than operative treatment [9,10]. Herein, we report a case of successful salvation of a solitary kidney in a patient with grade IV renal trauma by two sequential procedures of selective angioembolization and cystoscopic intra-cystic hematoma evacuation. Written informed consent for publication of the research details and clinical images was obtained from the patient.

A 52-year-old male patient who had lived with a solitary right kidney after donating his left kidney to his father 20 years ago was transferred to a nearby hospital due to right flank pain that occurred after a motorcycle accident. An AAST grade IV right kidney injury was found on abdominal computed tomography (Fig. 1). He was transferred to Gachon University Gil Medical Center for further treatment. When he arrived, his vital signs were as follows: systolic blood pressure, 100 mmHg; diastolic blood pressure, 60 mmHg; heart rate, 73 beats/min; respiratory rate, 15 breaths/min; and body temperature, 36.0°C. His Glasgow Coma Scale score was 15. On an abdominal computed tomography scan taken at a previous hospital, the lower pole of the right kidney was shattered, accompanied by extravasation of contrast (Fig. 1). The upper pole of the right kidney was relatively preserved. After a Foley catheter was inserted, gross hematuria with blood clots was identified. Because the patient presented in a hemodynamically stable condition, we decided to preserve the remaining kidney through selective renal artery embolization. Renal angiography (Fig. 2) demonstrated a pseudoaneurysm with a diameter of 0.7 cm at the anterior superior segmental artery, a pseudoaneurysm with a diameter of 0.1 cm at the anterior inferior segmental artery, and mild irregularity of the subsegmental arteries from the posterior inferior segmental artery. Embolization was performed on the pseudoaneurysm at the anterior superior segmental artery using a microcoil. Small lesions, which were suspicious for pseudoaneurysms, were observed in the anterior inferior segmental artery and the posterior inferior segmental artery, but no additional treatment was performed to preserve the viable kidney portion that would be damaged by embolization of the lesion. After embolization, the patient was transferred to the trauma intensive care unit. In the trauma intensive care unit, gross hematuria was shown. Continuous bladder irrigation (200 mL/hr) was performed. Nevertheless, the Foley catheter was frequently occluded due to clots. On the third day of hospitalization, we consulted an interventional radiologist for renal angiography to check the remnant bleeding focus. Renal angiography showed an arteriovenous fistula in the inferior pole in the right kidney (Fig. 3). Embolization with four microcoils (MicroNester with 2 mm/5 cm [Cook Medical, Bloomington, IN, USA], Concerto with 2 mm/4 cm [ Medtronic, Minneapolis, MN, USA], and two Concerto microcoils with 2 mm/8 cm [Medtronic]) was done to the blood vessel. Next, we consulted a urologist for evacuation of the bladder hematoma. Ellik evacuation was done to remove the bladder hematoma. There was no definite active bleeding site in the bladder. After that, there was no definite blood clot and hematuria through the Foley catheter. Clear urine was discharged through the Foley catheter at a rate of 80 to 170 mL/hr. His initial creatinine level was 1.26 mg/dL (glomerular filtration rate by the 2021 Chronic Kidney Disease Epidemiology Collaboration equation, 69 mL/min/1.73 m²) and his creatinine levels were checked daily. The highest creatinine level in his hospital stay was 1.69 mg/dL (glomerular filtration rate, 44 mL/min/1.73 m²) on the third day of hospitalization. On the next day, the creatinine level was 1.61 mg/dL (glomerular filtration rate, 51 mL/min/1.73 m²). There was no definite pulmonary edema on a chest X-ray or pitting edema in the bilateral lower extremities. On the fifth day of hospitalization, the patient was transferred to the general ward, and on the 10th day of hospitalization, the patient was discharged uneventfully.

We saved a solitary kidney through multiple procedures in a case of high-grade renal trauma, and this experience can be helpful for the management of solitary-kidney trauma. Although the patient had a high-grade kidney injury, we could easily refer the patient to an interventional radiologist for initial therapy due to the patient’s hemodynamic stability. Our hospital is a regional trauma center where an interventional radiologist is available at all times. Renal artery embolization was performed in a superselective manner to preserve the remaining kidney as much as possible. After follow-up for remnant suspicious bleeding foci, embolization was additionally performed through follow-up angiography.

According to the WSES and AAST guidelines, it is recommended to consider superselective embolization in hemodynamically stable or hemodynamically stabilized solitary-kidney patients [4]. Although controversial, some recent studies have suggested that renal artery embolization be performed even in hemodynamically unstable patients [11,12]. In hemodynamically unstable solitary-kidney patients, an option could be to perform renal artery embolization accompanied with sufficient resuscitation and critical care. Even if embolization is not supported or surgery is unavoidable due to delay in embolization, renal salvation procedures such as renorrhaphy or partial nephrectomy should be tried to save the kidney as much as possible. If a salvage operation is performed, insertion of a double-J stent will be helpful for the anticipated postoperative urinary leakage.

As in the case described herein, gross hematuria may cause Foley catheter occlusion, so caution should be taken, and cystoscopic evacuation of bladder hematoma is useful. It is known that the higher the AAST renal injury grade, the lower the remnant renal function, which is also correlated with the findings of dimercaptosuccinic acid renal scans [13]. There are no guidelines on using dimercaptosuccinic acid scans to monitor residual renal function after traumatic kidney injury. Further research could provide details on the relationship between observed remnant kidney function in solitary-kidney patients through dimercaptosuccinic acid and the patient's predicted prognosis.