Accuracy of sonography in detection of renal injuries caused by blunt abdominal trauma: a prospective study.

Background: This prospective study was conducted to evaluate the accuracy of sonography in detection of renal injuries caused by blunt abdominal trauma.

Methods: One hundred sixty-four patients (131 M, 33 F) with a history of recent blunt abdominal trauma who were stable enough to undergo both sonography and CT scan were included in this study. All of the cases had accepted indications for renal imaging. Ultrasound, as simultaneous gray scale B-mode scan and color-Doppler study, was achieved in all of the patients as the first imaging modality. Considering CT scan as the imaging modality of choice in evaluation of renal injuries caused by trauma, sonography findings were compared with CT scan results.

Results: Of the 164 patients referred for kidney sonography and CT scan, renal damage was detected in 103 cases by CT scan (63%). In 14 patients (13.5%), bilateral renal injuries were identified. Considering grading classification proposed by the American Association for the Surgery of Trauma (AAST), 57%, 24%, 9.5%, 6% and 3.5% of renal injuries were diagnosed as grade I, II, III, IV and V, respectively, by CT scan. Of the 164 patients, ultrasound results were consistent with renal damages in 66 cases (40%). Of these patients, signs of parenchymal hematoma, perinephric hematoma and pelvocaliectasis associated with internal echogenicity were the most prevalent ultrasound findings. Overall sensitivity and specificity of sonography in detection of renal injures were 48% and 96%, respectively, with a 0.8 positive predictive value, a 0.57 negative predictive value and an overall accuracy of 79%.

Conclusion: In spite of the availability and ease of performance of sonography in evaluation of trauma victims, this imaging modality has low sensitivity in detection of renal injuries and overlooks significant damages. CT scan should be considered as the diagnostic modality in victims of kidney trauma who are hemodynamically stable and have clear indications for renal imaging.