Blunt renal trauma: biomechanics and origination of renal lesions

Computer-assisted simulation of trauma is supposed to improve protective systems in traffic and risky leisure activities. In case of blunt renal injury biomechanical data being concerned with kidneys as a whole are extremely sparse. To enable three-dimensional simulations this study should supply important data of the renal biomechanics and elucidate the relationship between force distribution and origination of renal lesions.

The present study investigated 66 isolated uninjured porcine kidneys using a drop impactor. Changes in deformation, brake force of power, deceleration and intrapelvic pressure are depicted while varying energy application between 1.4 and 14.2J. Lesions were detected by cross-dissecting the organs into slices.

The measured values reflect a high correlation between load energy or brake force of power and deformation. Except the intrapelvic pressure all biomechanical parameters rise under increasing energy load. Comparing the different parameters over time a simultaneous concurrence of maximum brake force of power, deceleration and intrarenal pressure can be shown, the peak of deformation was reached belatedly.

The paths of biomechanical curves prove a viscoelastic behaviour of the kidney. In contrast to the literature the region principally bearing the load seems to be the collision zone between renal pelvis and cortex where first lesions appear. This is mainly caused by the fluid filled pelvis, an incompressible support, that is supposed to change its shape after exceeding energy application of about 4J.