Year : 2013 | Volume
: 29 | Issue : 3 | Page : 266--267
Diameter-axial-polar nephrometry: Has a better scoring system arrived?
Praveen Kumar Pandey
|How to cite this article:|
Pandey PK. Diameter-axial-polar nephrometry: Has a better scoring system arrived?.Indian J Urol 2013;29:266-267
|How to cite this URL:|
Pandey PK. Diameter-axial-polar nephrometry: Has a better scoring system arrived?. Indian J Urol [serial online] 2013 [cited 2020 May 26 ];29:266-267
Available from: http://www.indianjurol.com/text.asp?2013/29/3/266/117276
In this study, a retrospective analysis of case records of 299 patients who underwent open, laparoscopic, or robotic partial nephrectomy (PN) between January 2007 and May 2010 was performed.  The inclusion criteria were age >18 years, a contralateral radiological symmetrical kidney or data quantifying contralateral functional contribution, excision of a single tumor, availability of creatinine data before and after surgery, and availability of preoperative and postoperative contrast enhanced computerized tomography (CECT). The R.E.N.A.L. (radius, exophytic/endophytic properties, nearness of tumor to collecting system/sinus, anterior/posterior, location relative to polar lines) nephrometry scores, centrality index (C-index) scores, and novel DAP (DAP: Diameter-axial-polar) nephrometry scores were obtained simultaneously in all cases to describe the anatomical features of renal tumors.
DAP scoring utilized axial planar image sections on CECT to describe anatomical features of renal tumors. Diameter of the largest tumor was measured and scored as 1 if <2.4 cm, 2 if reported 2.4 to 4.4 cm, and 3 if found to be >4.4 cm. The axial distance of the edge of the tumor from the center of the kidney was measured and scored as 1 if >1.5 cm, 2 if reported ≤ 1.5 cm, and 3 if centre of tumor was touching or overlapping center point of the kidney itself. Polar distance of the tumor from the equatorial plane of kidney was calculated and scored as 1 if >2 cm, 2 if found ≤2 cm, and 3 if the tumor was visible at the middle plane of imaging. The final DAP score was calculated by adding these individual scores.
The interobserver agreement (IOA) for R.E.N.A.L., C-index, and DAP scores was 84, 90, and 95%, respectively. The association of nephrometry scores with percent functional volume preservation (PFVP), warm ischemia time (WIT), and operative estimated blood loss (EBL) was analyzed. On univariate analyses, all three scoring systems correlated with the analyzed perioperative outcomes. On multivariate linear regression, parameters of R.E.N.A.L. radius and nearness correlated with PFVP, parameters of nearness and polar location correlated with WIT, and parameters of radius and polar location correlated with EBL. The exophytic percentage and anterior/posterior location were not associated with the outcomes. The parameters of C-index centrality distance and diameter correlated with PFVP and WIT. Diameter of the tumor correlated with EBL but centrality distance did not. However, all DAP scoring parameters were associated with the analyzed clinical outcomes (each P < 0.001).
On statistical analysis, C-index score, diameter, and centrality distance values were distributed normally. None of the R.E.N.A.L. scoring parameters was normally distributed, although polar location scores were evenly distributed. However, final DAP and component scores were normally distributed. Diameter and nephrometry scores correlated significantly with PFVP and late percent glomerular filtration rate preservation (PGP), but DAP scoring showed the strongest association with PFVP (r 2 = 0.97) and PGP (r 2 = 0.81).
Nephron-sparing surgery (NSS) for T1a and some carefully selected T1b renal tumors leads to long-term survival and recurrence-free rates similar to radical nephrectomy.  Advancement in technologies such as thermal ablation, laparoscopy, and robotics has increased the spectrum of therapeutic options for renal tumors. Therefore, decision on optimal surgical management for these tumors requires data on size and location of the tumor.
To answer these demanding issues, Kutikov and Uzzo proposed the R.E.N.A.L. nephrometry scoring (RNS) for quantifying the anatomical features of renal tumors to assist surgical decision-making.  Ficarra et al. proposed the preoperative aspects and dimensions used for an anatomical (PADUA) classification to define the criteria for NSS based on anatomical features of tumors and to predict the risk of overall complications resulting from the surgery.  Simmons et al. devised the C-index to provide a quantitative description of a central tumor based on two-dimensional CECT images. 
An ideal scoring system should be simple enough, have maximum degree of IOA, and yield quantifiable data on surgical complexity of renal tumors. These scores should guide the surgeon in choosing the optimal surgical approach in these patients. Further, the scoring system should also comply with the perioperative outcome data.
RNS provides a comprehensive summary of features of tumors but is difficult to comprehend. The C-index lacks information on individual tumor features. DAP scoring integrates both these systems. DAP axial distance scoring measures distance of the tumor from a central axial reference point, in contrast to the collecting system, which is variable in different cases. Further, calculation of DAP polar distance does not require assignment of polar boundary lines as in RNS. However, DAP scores were obtained on manual measurements using basic image-viewing software which might be insufficient regarding accuracy of measurement.
None of these scoring systems has been established as a standard. DAP scoring promises to provide a clear understanding of the anatomy of renal tumors and its correlation with different clinical parameters. However, data from ongoing multi-institutional prospective studies with this novel scoring system are required to establish its consistency.
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