Isolated renal pelvis rupture due to blunt trauma presenting with low-density fluid accumulation around kidney on initial CT: A case report

Abstract

Back ground

Renal pelvis rupture due to trauma is commonly diagnosed in an excretory phase CT scan, which is not be applied in substantial proportion of trauma patients during initial evaluation. Since renal pelvis rupture has no specific findings, there is no clear indication to perform an excretory phase CT scan in the evaluation of trauma patients. We experienced a case presented with low-density fluid accumulation around kidney on plain CT imaging, subsequently diagnoses as having isolated renal pelvis injury.

Case presentation

68-year-old male fell from the second floor and referred to our institution. He had pain in his left buttock with a subcutaneous hematoma. He presented as blood pressure of 155 mmHg, heart rate of 145 beats/min, and blood test showed no specific abnormalities. Plain CT showed fluid accumulation around the left kidney, and following a contrast-enhanced CT scan at equilibrium phase showed no urinary extravasation. On the 4th hospital day, he complained of worsening back pain, and excretion phase of contrast-enhanced CT revealed left renal pelvic rupture. We placed a double-J ureteral stent for urinary drainage. Thereafter, disappearance of urinary extravasation without ureteral stricture was confirmed.

Conclusion

In patients with blunt trauma, perirenal effusion collection inconsistent with hemorrhage on CT imaging could be considered as a sign of isolated renal pelvic rupture.

Introduction

Isolated renal pelvis rupture has been reported in patients with chronic ureteral obstruction due to preceding conditions such as stone, pelvic mass, pregnancy, and malignancy [1,2]. Although trauma could cause isolated renal pelvis rupture, reported cases are limited and may be difficult to diagnose appropriately due to no specific findings or symptoms [1,2].

Computed tomography (CT) imaging of excretion phase was reported as method for diagnosis of isolated renal pelvis rupture [2]. However, contrast-enhanced CT with excretion phase is applied for selected trauma patients, which will not be applied in substantial proportion of trauma patients during initial evaluation.

We report a patient in which the retroperitoneal low-density fluid accumulation around kidney without hematoma on initial CT, subsequently diagnoses as having isolated renal pelvis injury.

Case presentation

68-year-old male accidentally fell down the stairs from the second floor and was transported to our emergency department. He had a systolic blood pressure of 155 mmHg, heart rate of 145 beats/min, respiratory rate of 25 breaths/min, and Glasgow Coma Scale score of 15.

He had pain in his left buttock with a subcutaneous hematoma 10 cm in diameter. Arterial blood gas analysis showed pH 7.442, pCO2 29.2 mmHg, pO2 74.6 mmHg, and lactate 0.8 mmol/L. Blood test was as follows: Hb 15.5 g/dL, Plt 165 × 10³/μL, BUN 26 mg/dL, Cr 0.89 mg/dL, CPK 717 U/L, D-dimer 19.4 μg/mL, Fibrinogen 320 mg/dL, PT-INR 0.75, APTT 22.7 s.

Whole-body CT for systematic trauma evaluation showed the retroperitoneal low-density fluid accumulation around the left kidney without the presence of high-density hematoma, and the images of equilibrium phase showed no leakage of contrast media from renal parenchyma, vessels, and urinary tract (Fig. 1). The patient was managed conservatively based on his hemodynamic status, and no ongoing anemia with no evidence of urinary tract injury.

Fig. 1.

Initial CT scan on admission.

a, b, c. Axial view of non-contract CT images through the retroperitoneum, arranged in the sequence of a, b and c, following a cranial-to-caudal direction. They showed fluid collection inconsistent with hemorrhage around the left kidney (arrowheads). Hounsfield unit value of accumulated fluid was 10 to 30, which suggested the accumulation was not hemorrhage or hematoma. d. Coronal view of contract-enhanced CT of equilibrium phase through the retroperitoneum shows the absence of oblivious renal pelvic rupture.

On the 4th hospital day, he complained of worsening back pain and presented gross hematuria. Contrast-enhanced CT with the excretion phase showed the contrast medium leakage from the left renal pelvis, leading to a diagnosis of renal pelvic rupture (Fig. 2). We placed a double-J ureteral stent for urinary drainage. A CT scan on the 23rd day confirmed the subtle fluid collection around the kidney and the disappearance of urinary extravasation. We removed the ureteral stent 2 month later, without any evidence of ureteral stricture.

Fig. 2.

Excretion phase of contrast-enhanced CT scan on the 4th day.

a Axial view. b Coronal view of maximum intensity projection. c Volume rendering. Excretion phase of contrast-enhanced CT showed contrast medium leakage from the left renal pelvis (arrows) on the 4th hospital day. This CT scan was taken with delay of 10 min after contrast material intravenous administration.

Discussion

Rapid increase of intraluminal pressure in ureter could result in injury at fragile site of ureter, i.e. renal pelvis, and urinary extravasation into the perinephric space would appear. This is suggested as a mechanism for isolated renal pelvic rupture [2,3]. Although neoplasms, stone, pregnancy, and medical procedures are described as causes of this condition, reported cases secondary to trauma are limited [2,4,5].

While we thoroughly assessed his past medical history related to obstruction of ureter or increase of intraluminal pressure of urinary tract in addition to the present diagnostic imaging, no specific etiology was detected. Therefore, we suggested the mechanism of renal pelvic rupture in this patient was trauma-induced pressure increase without no specific underlying condition.

As demonstrated in our patient, absence of major perinephric organ injury nor gross hematuria does not exclude renal pelvic rupture. Previous reports have shown that the diagnosis of renal pelvic injury can be confirmed by contrast medium leakage into the retroperitoneal space with deformation of the renal pelvis and ureteral dilatation on excretory phase CT [1,2,5]. For diagnosis of isolated renal pelvis injury in blunt trauma patients, excretory phase CT imaging has been also reported to be reliable to confirm [2]. However, retroperitoneal low-density fluid accumulation around kidney without hematoma on initial CT, presented in our case, has never been suggested as the sign of isolated collecting system injury. The possibility of renal pelvic injury may be suspected, when the retroperitoneal low-density fluid accumulation around the left kidney without hematoma was detected on CT, even with no macroscopic hematuria in patients with blunt trauma.

Conclusion

Renal pelvic rupture may occur without major kidney and adjacent organ injury. In patients with blunt trauma, perirenal effusion inconsistent with hemorrhage on CT imaging could be considered as a sign of isolated renal pelvic rupture.

CRediT authorship contribution statement

Yukiko Asanuma: Writing – review & editing, Writing – original draft, Data curation. Motoo Fujita: Supervision, Conceptualization, Data curation, Writing – review & editing. Tomomi Sato: Data curation, Supervision. Takuma Sato: Supervision. Shigeki Kushimoto: Supervision, Conceptualization.

Informed consent

Informed consent was obtained from the patient for the publication of this case report.

Approval of the research protocol

N/A.

Registry and the registration no. of the study/trial

N/A.

Animal studies

N/A.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.