Analysis of the Biomechanical Response of Kidneys Under Blunt Impact

Objective. This study addresses the biomechanical response of isolated kidneys to traumatic insult.

Methods. Kidneys were subjected to blunt impact by using a freely swinging right cylindrical pendulum. Force-deformation characteristics were derived for 65 impacted adult pig kidneys. Renal injuries were classified by autopsy, and an injury risk analysis was performed. In addition a finite element model that simulated the experiments was implemented.

Results/Conclusions. The kidneys showed a viscoelastic response. An energy-based injury threshold was identified, with a strain energy density of 21 kJ/m³ corresponding to a 50-percent risk of renal injury level AIS3 or higher. Finally, the impact tests were simulated using a finite element model of the kidney to investigate relevant injury mechanisms. The model predicted the renal capsule and underlying parenchyma to first fail at an impact energy level of 4.0 J, consistent with experimental results.

Keywords:

• Kidney
• Blunt Impact
• Abdomen
• Biomechanics

ACKNOWLEDGMENTS

We are gratefully indebted to our colleagues Dr. Markus Muser (Working Group on Accident Mechanics, Zurich, Switzerland) and Dr. Franz R. Schmidlin (Department of Urology, University Hospital, Geneva and Clinique des Grangettes, Chène-Bougeries, Switzerland) for their support, insight, and help.