Pseudoaneurysm of the Left Renal Segmental Artery With Delayed Detection After Blunt Trauma

Introduction

Pseudoaneurysms of the kidney can occur following penetrating renal trauma, renal surgery, or renal biopsy, and may cause delayed bleeding [1,2]. Renal pseudoaneurysm is a contained arterial wall disruption in which blood forms a cavity that communicates with the arterial lumen, typically confined by the adventitia or perivascular tissue [1]. Although cases following blunt trauma are rare, they may become apparent in a delayed fashion after initially negative imaging [3–5]. Pseudoaneurysm rupture can be life-threatening, necessitating early detection and intervention [1]. In cases of severe renal injury or concomitant urinary fistula, mechanical or chemical stimuli can contribute to delayed pseudoaneurysm formation [6,7]. This case report describes a delayed pseudoaneurysm detection arising from a left renal segmental artery following blunt trauma.

Case Report

A 52-year-old man was transferred to our advanced emergency and critical care center after a motorcycle accident. He sustained blunt trauma to the left side in a motorcycle accident. After being transported to a nearby hospital by emergency medical services, he was transferred to our hospital’s advanced emergency care center on the same day for treatment of multiple trunk injuries. At admission, vital signs were respiratory rate 25 breaths/minute, pulse rate 78 beats/minute, blood pressure 107/80 mmHg, and body temperature 36.9°C. He had no significant medical comorbidities and was not taking any anticoagulant or antiplatelet medications. His height was 170 cm and weight was 77 kg (body mass index, 26.6 kg/m2). Baseline renal function was preserved (serum creatinine level, 0.83 mg/dL; estimated glomerular filtration rate, 76.5 mL/min/1.73 m2). Physical examination revealed tenderness in the left chest and gross hematuria. Blood tests showed a decrease in hemoglobin from 15.1 g/dL to 13.2 g/dL, compared with the previous hospital. An indwelling urethral balloon catheter (Foley catheter) was inserted on admission for strict urine output monitoring and management of gross hematuria. A contrast-enhanced computed tomography (CT) scan revealed fractures of the left fourth to tenth ribs, left hemothorax, left renal injury (American Association for the Surgery of Trauma [AAST] Grade III), and splenic injury (AAST Grade IIIa or IIIb), with extravasation of contrast agent (Figure 1). An emergency angiography was performed for hemostasis, and transcatheter arterial embolization (TAE) was performed on the spleen. Selective angiography of the left renal segmental artery showed no obvious extravasation, and conservative management was chosen (Figure 2). During the early hospitalization, the patient was placed on activity restriction (repositioning was allowed, and head-of-bed elevation was limited to 30°), and mobilization was gradually increased after physician clearance. Red blood cell transfusion was administered twice during hospitalization: 2 units on post-injury day 3 for worsening anemia with a tendency toward tachycardia, and 4 units on post-injury day 12 for persistent gross hematuria associated with anemia and systemic inflammation. The patient developed fever on day 5 after injury. The next day, a contrast-enhanced CT scan was performed to identify the source of fever, revealing that the perirenal hematoma was resolving but showing a low-attenuation area with fluid retention, suggestive of an abscess (Figure 3A). Subsequently, hematuria, which had initially improved, worsened, and progressive anemia was noted, prompting further evaluation on day 12 after injury. A new finding suggestive of a pseudoaneurysm in the left kidney was identified on contrast-enhanced CT, prompting the performance of TAE using n-butyl-2-cyanoacrylate and microcoils (Figures 3B, 4). Additionally, retrograde ureterography revealed contrast agent leakage from the left lower renal pelvis into the retroperitoneum, leading to a diagnosis of a ureteral fistula, and a ureteral stent was placed (Figure 5). Subsequently, fever and hematuria improved, and the patient was moved to the urology ward from the emergency center on day 20 after injury. Medications at the time of transfer to the urology ward included analgesics and gastroprotective agents, along with supportive bowel regimen. The urethral catheter was removed on day 47 after injury, briefly reinserted on day 50 for a febrile episode, and removed again on day 58. The double-J ureteral stent (placed on day 12) was exchanged on day 45 and removed on day 124 (planned day 96 but deferred due to fever), with follow-up at a local urology clinic.

Discussion

Renal pseudoaneurysms are primarily caused by penetrating injuries and are known to be a cause of delayed bleeding. However, cases occurring after blunt trauma are rare [2,4], and reports similar to the present case are scarce.

The mechanism of pseudoaneurysm formation is thought to involve temporary hemostasis of the injured vessel due to hypotension or coagulation reactions after injury, followed by recanalization of the injured vessel due to thrombolysis around the injury site, leading to the development of a pseudoaneurysm [2,3]. In the present case, no extravascular leakage was observed in the left renal segmental artery on angiography at the day of injury, and we considered that a pseudoaneurysm formed after a certain period following the injury, leading to delayed bleeding. For the treatment of pseudoaneurysms, TAE is a minimally invasive and effective option [8,9]. However, in cases like this one, in which contrast agent extravasation or pseudoaneurysms are not detected on initial imaging, the use of prophylactic arterial embolization should be approached with caution [8,9]. If nonsurgical treatment, including interventional radiology, is selected, it is advisable to perform imaging re-evaluation within at least 2 weeks of injury, considering the extent of injury and post-hospitalization course, to strive for early detection of delayed pseudoaneurysms [8,9]. It is also possible that such urine-derived chemicals, by accumulating in local tissues due to urinary incontinence, provided chronic inflammatory stimuli to the cellular environment near damaged vessels, thereby promoting structural weakening of the vascular wall. Therefore, caution is warranted regarding the development of pseudoaneurysms in cases of renal injury complicated by urinary leakage.

Regarding the timing of pseudoaneurysm formation, most reports indicate that it occurs approximately 10 days to 2 weeks after injury [2,4]. In this case, retrospective analysis revealed that on CT performed on day 6 after injury, there was irregular fluid accumulation around the kidney suggesting urine overflow, along with partial contrast enhancement within the renal parenchyma (Figure 3A). These findings are consistent with the possibility of rebleeding from a temporarily hemostased vessel or an early-stage pseudoaneurysm, which may suggest that earlier recognition could have been possible. While the necessity of routine CT follow-up after injury remains debatable, repeat imaging should be considered when clinical deterioration occurs, such as fever, worsening pain, recurrent gross hematuria, or decreased hematocrit levels [5], and early repeat imaging (eg, within 24–48 hours) may be useful in high-grade renal injury [8]. In addition, when nonoperative management, including interventional radiology, is selected, imaging re-evaluation within approximately 2 weeks of injury may facilitate earlier detection of delayed pseudoaneurysms, depending on the injury severity and clinical course [8,9].

For the treatment of pseudoaneurysms, TAE is a minimally invasive and effective option [8,9]. However, in cases like this one, in which contrast agent extravasation or pseudoaneurysms are not detected on initial imaging, the use of prophylactic arterial embolization should be approached with caution [8,9].

Conclusions

Minimally invasive endovascular treatment was effective for this traumatic renal segmental artery pseudoaneurysm, which can develop after blunt trauma as well as penetrating injury and may be detected only on follow-up imaging. In severe injury or concomitant urinary extravasation/urinary fistula, repeat imaging during the acute phase should be considered because urinary leakage may contribute to its formation.