OBJECTIVE To create a model intended to more accurately characterize renal function alteration after partial nephrectomy using a combination of renal scintigraphy and estimated glomerular filtration rate (eGFR). METHODS Thirty-two partial nephrectomy patients from a single center with preoperative and postoperative renal scans were reviewed. Renal scan data were used to calculate proportional eGFR in the involved kidney as a product of the percentage function of the operated kidney and total eGFR. Linear regression models were created to describe endpoints (postoperative eGFR, involved kidney percent function, proportional eGFR) as functions of clinical variables associated with kidney damage. RESULTS For the ipsilateral kidney, mean preoperative percent function and eGFR were 50% (SD, 4.8) and 31 mL/min/m(2) (SD, 3.4), respectively; postoperative percent function and involved kidney eGFR were 44% (SD, 9.0) and 27 mL/min/m(2) (SD, 9.0), respectively. Decreased postoperative proportional eGFR was significantly associated with increased clamp time and tumor size in univariate linear regression models. Clamp time was associated with total eGFR, where tumor size was not. Additionally, clamp time and tumor size explain more of the variation in proportional eGFR (R(2) = 0.39 and R(2) = 0.17, respectively), compared to percent effort and total eGFR. CONCLUSIONS Proportional eGFR has a stronger association with putative factors of renal dysfunction after partial nephrectomy, including clamp time and tumor size, compared to total eGFR, indicating it may be a more sensitive marker of renal function after partial nephrectomy.