The effect of PERC on renal function has been examined in an animal model by several groups. In one porcine model, the baseline renal function, as defined by PAH and creatinine clearance, was compared to that measured at one month post-procedure. No acute data were recorded, but the authors did note that although there was no significant change in renal function at the one month follow-up point, there was a significant amount of renal scarring present. This finding of significant renal scarring following PERC in an animal model has been corroborated by others. One group has studied a canine model, and detected a significant diminution of renal function (defined by creatinine clearance) at 48 hours following PERC, and at 6 weeks following PERC renal function returned to normal. In human subjects undergoing PERC, percutaneous tracts have also been associated with renal scarring. These studies, both retrospective case series, did not capture strictly defined measures of renal function, such as creatinine clearance, but rather compared pre- and post-procedure serum creatinine as a surrogate for renal function. No significant change in serum creatinine was identified in either study, but blood collections were performed at variable times, in uncontrolled settings.