EURURO Vol. 72 No. 5

e131 860

Letter to the Editor
Re: Julien Dagenais, Matthew J. Maurice,
Pascal Mouracade, Onder Kara, Ercan Malkoc,
Jihad J. Kaouk. Excisional Precision Matters:
Understanding the Influence of Excisional
Volume Loss on Renal Function After Partial
Nephrectomy. Eur Urol 2017;72:168–70.
Recently, Dagenais et al [1] reported the impact of
excisional volume in recovery[1_TD$DIFF] of renal function after partial
nephrectomy (PN). Using single cohort data from a high-
volume tertiary care center, they showed that excisional
precision was a significant factor for postoperative renal
function; however, several issues need clarification, to
better understand the study.
First, a validated formula was used to calculate the
glomerular filtration rate (GFR). However, the separate GFR
for each kidney could not be determined, which hindered
the direct measurement of GFR for the partially excised
kidney. Using direct measurement of GFR including
diethylenetriaminepentaacetic acid or mercaptoacetyltri-
glycine renal scintigraphy for both kidneys [2] could yield a
more objective outcome.
Second, in terms of study design[2_TD$DIFF], patients with positive
margins (5.6%) should be excluded from the analysis. Cases
with positive margins cannot be regarded as cases with
[11_TD$DIFF]precise excision[3_TD$DIFF]. [12_TD$DIFF]Also, in the statistical analysis, authors
performed logarithmic transformation to overcome the
skewed distribution of excised volume; however, because
the excised volume was distributed with heavy skew,[13_TD$DIFF] a
gamma distribution [14_TD$DIFF]must be more appropriate.
Fourth, this study focused on patients with normal renal
function with mean GFR of 84.8 (range, 69.0–97.7); hence,
the results need to be further validated in a cohort of
patients with chronic kidney disease (CKD) or in patients at
risk for [15_TD$DIFF]de [16_TD$DIFF]novo or [17_TD$DIFF]exacerbation of CKD. In actual clinical
practice, the change of GFR within normal or [18_TD$DIFF]near normal
renal function is less important than the change observed in
[19_TD$DIFF]those patients [20_TD$DIFF]with [21_TD$DIFF]CKD. Lastly, although[22_TD$DIFF] limiting the
excised volume[5_TD$DIFF] is important to[6_TD$DIFF] better[23_TD$DIFF] preserve renal
function, there are few options to minimize the excised
volume while [24_TD$DIFF]ensurng [25_TD$DIFF]a negative surgical margin. Maurice
et al [3] previously reported that[26_TD$DIFF] performance of robotic
approach by trained surgeons and [27_TD$DIFF]limiting blood loss are
modifiable factors to minimize the loss of healthy
parenchyma during PN. [28_TD$DIFF]However, Dong et al [4] reported
that excised parenchyma volume was not correlated with
functional outcomes[7_TD$DIFF], [29_TD$DIFF]but [30_TD$DIFF]performance [31_TD$DIFF]of PN by experienced
surgeons was strongly associated with global and ipsilateral
renal function [32_TD$DIFF] preservation.
Interestingly, Zhang et al [5] reported an insignificant
association between preserved renal function and ischemia
time or tumor complexity in a single center study with a
large cohort. In their study, parenchyma volume loss and
ischemia time [33_TD$DIFF]affected the acute functional recovery;
however, most kidneys eventually recovered[10_TD$DIFF] 88–90%, even
in cases with Grade 2 or 3 acute kidney injury. Longitudinal
[34_TD$DIFF]studies using an objective measurement tool including
renal scan [35_TD$DIFF]are warranted to clarify the importance of
excisional volume loss not only in patients with normal
renal function [36_TD$DIFF], but also in patients with CKD and those at
risk for CKD.
Conflicts of interest: The authors have nothing to disclose.
Acknowledgments: This work was supported by the Soonchunhyang
University Research Fund.
References
[1]
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[2]
[3]
[4]
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[5]
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ava ilable at
journal homepage:
DOI of original article: .
0302-2838/# 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.