Preservation of Renal Architecture During Extracorporeal Shock Wave Lithotripsy*

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Abstract
Acute renal morphologic and functional changes after extracorporeal shock wave lithotripsy are thought to be attributable to two distinct mechanisms: direct cellular injury from the shock wave energy or indirect injury secondary to relative ischemia from capillary disruption and tissue edema. In an effort to protect the renal parenchyma from damage by hypoxic injury, we evaluated four pharmacologic agents with previously documented protective effects against hypoxemia. Female New Zealand white rabbits (4.4 kg) were placed in metabolic cages and underwent 48-hour urine collections for total volume and creatinine. Nonmedicated rabbits (control) and rabbits that had been medicated with either mannitol (500 mg/kg IV), verapamil (0.1 mg/kg IV), enalapril (0.1 mg/kg IV) or allopurinol (10 mg/kg PO) received 2000 shocks at 1140 bar to the lower pole of the right kidney on a piezoelectric lithotripter (Wolf Piezolith 2300). A sixth group, receiving only ketamine and xylazine anesthesia along with one of the selective medications, served as sham-treated animals. Renal functional and morphologic changes were evaluated 30 days post-lithotripsy. Renal functional studies with creatinine clearance determinations revealed no significant difference between the control and treatment groups (P > 0.8). A significant reduction in the volume of permanent injury sustained with lithotripsy was noted in the allopurinol-treated group compared with the control animals (P < 0.001). A reduction in the mean volume of tissue injury was also seen with the enalapril- and mannitol-treated animals, but this decrease was not statistically significant (P > 0.1). Our results suggest that acute renal morphologic changes of lithotripsy may be attenuated by pretreatment with allopurinol. Whether this reduction in the area of injury can be substantiated in a large number of animals or in alternative animal models that more closely represent the human kidney remains to be determined.