Open Access

ARTICLE

Serum creatinine can be used as a surrogate for glomerular fi ltration rate in single renal unit models

Ofer N. Gofrit, Marcelo A. Orvieto, Kevin C. Zorn, Gary D. Steinberg, Gregory P. Zagaja, Arieh L. Shalhav

1 Section of Urology, Department of Surgery, University of Chicago Hospitals, Chicago, Illinois, USA
Department of Surgery, Section of Urology, University of Chicago, Chicago, Illinois, USA
Address correspondence to Dr. Ofer N. Gofrit, Department of Surgery, Section of Urology, The University of Chicago Hospitals, 5841 S. Maryland Avenue, MC 6038, Chicago, IL 60637 USA

Canadian Journal of Urology 2009, 16(1), 4452-4457.

Abstract

Background and purpose: Single renal unit models are invaluable for studies in renal physiology, transplantation and response to ischemic injury. Glomerular filtration rate (GFR) is commonly used for evaluation of renal function. Measuring the GFR involves relatively complicated and expensive systems. In this study we determined whether serum creatinine (Scr) can predict the GFR in this model.
Materials and methods: Right laparoscopic nephrectomy was performed in 46 female pigs weighing 25 kg-30 kg. Twelve days later the left kidney was exposed to various periods of warm ischemia (30, 60, 90, and 120 minutes). Scr and GFR (using the iohexol clearance method) were determined preoperatively and at postoperative days 1, 3, 8, 15, 22 and 29. A total of 244 pairs of Scr and GFR values were analyzed to determine a formula for predicting GFR (pGFR) from Scr.
Results: Scr range was 1.2 mg/dl -29 mg/dl and GFR range was 1.8 ml/min -180.5 ml/min. The empiric formula deduced from the database for calculating pGFR from Scr was: pGFR = (217 divided by Scr) minus 0.2. pGFR correlated well with the actual GFR (R² = 0.85). The graphs for pGFR were almost indistinguishable from the graphs for actual GFR in every single animal. The results and conclusions of the experiments using either actual or predicted GFR were identical.
Conclusions: We conclude that in a single renal unit porcine model using ischemia as the insult to the kidney, expensive actual measurements of GFR can be reliably replaced by Scr based calculated GFR.

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