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R.E.N.A.L. Nephrometry Score is a Surrogate for Surgical Difficulty
Tom S Floyd, Jr.1, Jennifer Davila-Aponte1, Kasey Morrison1, Lorna Herbert2, Noah Schenkman1, Tracey L Krupski1
1University of Virginia, Charlottesville, VA;2UCLA, Los Angeles, CA
Introduction: As health care costs increase, so does the demand for comparative efficacy studies. Surgical efficacy studies are problematic as technical complexity is difficult to quantitate. The RENAL nephrometry score (NS) is a standardized system for describing kidney tumors attempting to quantify surgical complexity. Aside from one observational report, these Methods have not been externally evaluated. We tested the hypothesis that higher NS correlates with surgical difficulty during partial nephrectomy (PN).
Materials & Methods: Using a retrospective database of laparoscopic or open PN performed from 2005-2010 containing patient demographic data, operating details and post-operative glomerular filtration rate (eGFR). CT or MRI scans were used to generate RENAL NS. Surgical difficulty was defined by blood loss, operating room time, ischemia time (IT) and length of stay, while eGFR was considered indicative of post-operative renal function. Univariate and multivariate analyses identified associations among the measured characteristics. All statistical analysis used SAS 9.2.
Results: In 139 patients, higher NS correlated with IT in both univariate (p=0.0002) and multivariate analysis (p=0.0010) when controlling for potential confounders. NS also correlated significantly with post-operative eGFR in univariate analysis (p = 0.0302) and displayed a trend in multivariate analysis (p=0.0824). NS was not correlated with other surrogates for surgical complexity.
Conclusions: Surgical clamp time is a logical surrogate for technical difficulty. Higher RENAL NS strongly predicted surgical clamp time during PN suggesting it serves as substitute for clinical judgment. NS may also reflect long term outcome of PN, as reflected by its correlation with post-operative GFR.
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