UROGENITAL TRAUMA

Validity of computerized tomography in blunt renal trauma
Bschleipfer T, Kallieris D, Hallscheidt P, Hauck EW, Weidner W, Pust RA
Department of Urology, Ulm Military Hospital, Ulm / Donau, Germany
J Urol. 2003;170: 2475-9

• Purpose: Improved imaging techniques and new therapeutic possibilities require rethinking the indication for laparotomy with regard to blunt renal trauma. Refined classification systems would facilitate the decision relating to therapy but they are based on knowledge of the imaging accuracy of computerized tomography (CT). We evaluated the validity of the CT depiction of renal injuries.
• Materials and Methods: A total of 42 porcine kidneys were subjected to traumatization of various degrees. They then underwent CT examination and were subsequently cross-dissected into slices 3 mm thick. The comparative evaluation involved 2,080 CT images and 1,819 macroscopic sectional views, which showed 3,521 and 3,778 individual lesions, respectively.
• Results: Using CT the overall extent of injury in renal trauma was only slightly overrated at an average of 15% higher than that seen on macroscopy. Simple linear lesions tended to be over assessed and parenchymal destruction tended to be under assessed. Central lesions were depicted more frequently than peripheral lesions. CT of medullary lesions and parenchymal detachment was not feasible.
• Conclusions: CT of the kidney enables the distinction of different kinds of lesions and their localization well. Pelvic structures or vessels can imitate linear lesions. However, this imaging procedure can be used as a basis for refining categorization systems for blunt renal trauma. It can also be used to obtain a large quantity of lesion data for biomechanical investigations.
  
  
• Editorial Comment
  Computed tomography (CT) is the undisputed state of the art when it comes to evaluating renal injuries. However, despite wide use, and a number of clinical studies supporting its accuracy, few experimental studies have been published which evaluate the accuracy of CT scanning in renal trauma. Although this study has some shortcomings inherent in the use of animals (experimental model of renal injury may or may not model human injuries well, pig kidneys may not be identical to human kidneys, etc.) it is a valuable experimental look at the correlation between CT imaging and known renal injuries.
  In this study, 42 pig kidneys underwent experimental injury and over 2,000 CT images of the kidneys were compared to macroscopic sections of the injured renal units. They concluded: 1) CT overestimates the degree of injury (as scored by the authors own scoring system) by only 15%, 2) Parenchymal disruption is slightly overestimated because of the confounding appearance of normal renal tissue such as blood vessels.
  The authors made no attempt to model vascular injury or penetrating injury. Also, they did not attempt to validate CT in evaluating renal trauma in line that corresponded to the 5-part American Association for the Surgery of Trauma (AAST) Organ Injury Severity Scale for the Kidney. However, this study appears to lend experimental support to the common clinical practice of using CT to accurately determine the extent of blunt renal injury.

Dr. Richard A. Santucci
Assistant Professor of Urology
Wayne State University
Detroit, Michigan, USA