Feasibility of an Isolated Kidney Perfusion Model for Postmortem Interval Estimation in a Rabbit Model: A Pilot Study

Background: The estimation of the postmortem interval (PMI) remains a complex challenge in forensic medicine. While macroscopic, biochemical, and molecular methods are well-documented, postmortem functional approaches at the organ level are largely underexplored. This pilot study investigated the feasibility of utilizing an isolated ex vivo kidney perfusion model to assess residual postmortem renal function-specifically glomerular filtration and tubular solute handling-as a potential chronological marker for PMI. Methods: Sixteen adult New Zealand rabbits were euthanized and randomly assigned to four postmortem interval groups (1, 5, 10, and 15 h). An unoxygenated, room-temperature crystalloid perfusion system was established to mimic natural postmortem decay. Initially, 32 kidneys were perfused; two were excluded due to anuria, resulting in 30 successfully analyzed kidneys. To strictly eliminate pseudoreplication bias, bilateral functional data were mathematically aggregated at the subject level, establishing the individual rabbit (n = 16) as the statistical unit. Results: Following statistical adjustment at the subject level, none of the measured functional parameters exhibited statistically significant chronological variation across the postmortem intervals (all p > 0.05; statistical significance defined as p < 0.05). Glomerular filtration was profoundly depressed across all groups, with adjusted inulin clearance ranging between 0.0031 and 0.0086 mL/min/g (peaking nonsignificantly at 10 h). Furthermore, active tubular reabsorption was virtually nonexistent; calculated reabsorbed loads for evaluated solutes, particularly potassium and sodium, yielded predominantly negative values. This phenomenon indicates a complete absence of physiological active reabsorption, reflecting instead a massive passive leakage of intracellular electrolytes into the tubular fluid due to cellular autolysis. Conclusions: Within this specific experimental setup, the isolated kidney perfusion model failed to demonstrate reproducible, time-dependent renal function useful for PMI estimation. These findings indirectly suggest that, unlike the prolonged supravital physiological resilience observed in skeletal muscle, highly metabolically active renal tissue rapidly loses its complex functional capacity following somatic death. Future studies exploring supravital renal function should consider targeting the immediate early postmortem period (0-1 h) or integrating advanced organ preservation techniques to unmask residual cellular capabilities.