Imaging assessment of renal injuries in children and adolescents: CT or ultrasound?

Renal ultrasound to evaluate for blunt renal trauma in children: A retrospective comparison to contrast enhanced CT imaging

INTRODUCTION

The standard imaging modality for hemodynamically stable blunt abdominal trauma patients is a contrast enhanced CT scan, which is reflected in the current AUA urotrauma guidelines. This comes, however, with radiation exposure and the potential sequalae of IV contrast administration in the pediatric patient.

OBJECTIVE

We hypothesize that ultrasound imaging would be able to diagnose and rule out clinically significant renal injuries when compared to the gold standard of CT scan in the setting of pediatric blunt abdominal trauma.

STUDY DESIGN

All children <18 years of age who were evaluated for blunt abdominal trauma who had a CT scan and ultrasound imaging of kidneys were identified. The ultrasound images were reviewed by four reviewers who were blinded to CT results and all clinical information. The ability of ultrasound to diagnose and rule out clinically significant renal injury was evaluated by diagnostic test performance characteristics including sensitivity, specificity, negative predictive value and positive predictive value.

RESULTS

There were 76 patients identified, 24 of which had a renal injury (1 bilateral) diagnosed by CT scan for a total of 25 injuries in 152 renal units. There were six grade I-II injuries and 19 grade III-V injuries. The sensitivity of the four blinded reviewers by ultrasound alone to detect the 19 grade III-V injuries ranged from 79 to 100% with NPV between 97 and 100%. Three of the four reviewers identified all 19 grade III-V injuries by ultrasound. When combined with significant hematuria, all 19 grade III-IV injuries were identified. Of note, all patients with a grade III-V injury of the kidney had significant hematuria. Of the grade I-II renal injuries, all reviewers identified 1/5 or 2/5 by ultrasound alone.

DISCUSSION

The limitations of this study include: its retrospective nature, limited number of patients and reviewers, quality of the ultrasound machine. and experience of technologist, radiologist and urologist. A major limitation is the inability to assess other solid organ injuries during this initial study.

CONCLUSIONS

When compared to a CT scan as the gold standard, kidney ultrasound images had a sensitivity of 79-100% to detect grade III-V injuries and NPV of 97-100% by four blinded reviewers. All grade III-V injuries had either an episode of gross hematuria or microscopic hematuria >50 RBC/hpf. A prospective study that includes full abdominal imaging is needed to confirm that ultrasound can safely be used in place of CT scan for evaluation of hemodynamically stable blunt trauma patients.

European Society of Paediatric Radiology abdominal imaging task force: recommendations for contrast-enhanced ultrasound and diffusion-weighted imaging in focal renal lesions in children

Contrast-enhanced ultrasound (CEUS) and diffusion-weighted imaging (DWI) are safe, repeatable imaging techniques. The aim of this paper is to discuss the advantages, technical factors and possible clinical applications of these imaging tools in focal renal lesions in children.

Point-of-Care Ultrasound Evaluation of Severe Renal Trauma in an Adolescent

Traumatic renal injuries are more common in pediatrics because of the relatively larger size of the kidneys in the pediatric patient. Although computerized tomography remains the criterion standard for the initial evaluation of blunt renal trauma, there is evidence that renal ultrasound may serve a role in postinjury surveillance. Here, we present a case in which point-of-care ultrasound was used to image severe blunt renal trauma in a 17-year-old adolescent boy. In this case, point-of-care ultrasound identified severely distorted renal parenchyma after a grade 5 renal laceration was identified on computerized tomography scan.

Renal trauma: imaging evaluation and implications for clinical management

Severe renal injuries are usually associated with multisystem injuries, may require interventional radiology to control hemorrhage and improve the chances for renal salvage, and are more likely to fail nonoperative management. However, most renal injuries are mild in severity and successfully managed conservatively. The AAST classification is the most widely used system to describe renal injuries and carries management and prognostic implications. CT with intravenous contrast is the imaging test of choice to assess for renal injuries. Contrast extravasation indicating active bleeding should be mentioned as its presence is predictive for failure of nonoperative management. Radiologists play a critical role in identifying renal injuries and should make every effort to describe renal injuries according to the AAST grading scheme to better inform the surgeon's management decisions.