CUAJ • February 2011 • Volume 5, Issue 1
© 2011 Canadian Urological Association
Original research Original research
Background: Radiographic characteristics may be associated with
the degree of renal function preservation following partial nephrec-
tomy. The purpose of this study was to determine the impact of
preoperative radiographic variables on change in renal function
using 24-hour urine creatinine clearance (uCrCl).
Methods: Patients with partial nephrectomy performed from
November 2003 to 2008 were enrolled in the study. Serum cre-
atinine and 24-hour urine was collected preoperatively and at
3, 6 and 12 months postoperatively. Computed tomography or
magnetic resonance imaging was used to determine tumour size,
tumour location and renal volume.
Results: Of the 36 patients, median age was 62 (range 30-78) and
21 (58%) were male. The mean tumour diameter was 2.8±1.4 cm.
Twenty-two (61%) tumours were located at the renal pole and
11 (31%) were endophytic. Overall, mean preoperative uCrCl
was 88.8±34.2 mL/min and mean postoperative uCrCl was
82.8±33.6 mL/min (6.8%; p < 0.01). On multivariable analysis,
no single characteristic was associated with a clinically prohibitive
decrease in renal function (-9.4% if endophitic, p = 0.06; -0.57%
per cm diameter, p = 0.73; and -6.9% if located at the renal pole,
p = 0.15). The total renal volume was also not significantly asso-
ciated with renal function change (-1.1% per 100 cc, p = 0.86).
Interpretation: Preoperative radiographic characteristics seem to
be associated with small changes in renal function following partial
nephrectomy. These data support renal functional benefits of partial
nephrectomy regardless of tumour size and location.
Cite as: Can Urol Assoc J 2011;5(1):45-8; DOI:10.5489/cuaj.10011
Contexte : Les caractéristiques radiographiques peuvent être asso-
ciées au niveau de préservation de la fonction rénale après une
néphrectomie partielle. L’objectif de l’étude était d’évaluer l’impact
de variables radiographiques préopératoires sur les variations de la
fonction rénale à l’aide de la mesure de la clairance de la créatinine
dans les urines recueillies sur 24 heures (ClCrU).
Méthodologie : Des patients ayant subi une néphrectomie partielle
entre novembre 2003 et 2008 ont été admis à l’étude. On a mesuré
la créatinine sérique et recueilli les urines sur 24 heures avant
l’opération, puis 3, 6 et 12 mois après l’opération. La taille et le
siège de la tumeur et le volume rénal ont été déterminés par tomo-
graphie par ordinateur ou par imagerie par résonance magnétique.
Résultats : L’âge médian des 36 patients admis était de 62 ans
(entre 30 et 78 ans); 21 patients (58 %) étaient des hommes. Le
diamètre moyen de la tumeur était de 2,8 ± 1,4 cm. Vingt-deux
tumeurs (61 %) étaient situées à un pôle rénal et 11 (31 %) étaient
endophytiques. De façon globale, la ClCrU moyenne avant et après
l’opération était de 88,8 ± 34,2 mL/min et de 82,8 ± 33,6 mL/min
(6,8 %; p < 0,01), respectivement. Selon l’analyse multivariée,
aucune caractéristique particulière n’était associée à une réduc-
tion cliniquement excessive de la fonction rénale (-9,4 % pour les
tumeurs endophytiques, p = 0,06; -0,57 % par cm de diamètre,
p = 0,73, et -6,9 % si la tumeur était située à un pôle rénal, p =
0.15). Le volume rénal total n’était pas non plus associé de façon
significative à une variation de la fonction rénale (-1,1 % pour
100 mL, p = 0.86).
Interprétation : Les caractéristiques radiographiques préopératoires
semblent associées à de petites variations de la fonction rénale
après une néphrectomie partielle. Ces données appuient les avan-
tages liés à la fonction rénale de la néphrectomie partielle, peu
importe la taille et le siège de la tumeur.
Surgical excision is the most effective treatment for patients
with primary renal malignancy. In the past, partial nephrecto-
my was performed exclusively on patients with a solitary kid-
ney, bilateral renal tumours or renal insufficiency. However,
this operation is now preferred in many other patients given
equivalent cure rates compared to radical nephrectomy.1-7
Moreover, recent data reveal that partial nephrectomy
patients with a normal contralateral kidney and normal
preoperative renal function have improved long-term renal
function2,8-11 and possibly improved overall survival.12,13 Thus,
the most recent American Urological Association guideline
recommends partial nephrectomy as the treatment of choice
for the management of clinical stage 1 renal masses, even in
those with a normal contralateral kidney.14
Despite the advantages over radical nephrectomy, partial
nephrectomy also results in loss of functioning nephrons due
to resection of normal parenchyma, intraoperative ischemia
Rodney H. Breau, MD, FRCSC;* Aaron T.D. Clark, MD;† Chris Morash, MD, FRCSC;† Dean Fergusson, PhD;±
Ilias Cagiannos, MD, FRCSC†
Associations between radiographic characteristics and change in
renal function following partial nephrectomy using 24-hour
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CUAJ • February 2011 • Volume 5, Issue 1
Breau et al.
and other physical/chemical trauma secondary to surgery.
Since, tumour size and location may predict the severity
of nephron loss, these measurements may be important
variables in determining which patients will benefit most
from partial nephrectomy.10 Furthermore, the proportional
loss in renal function may depend on the baseline contribu-
tion of renal function from the affected kidney. Despite the
theoretical utility of kidney and tumour characteristics, the
association between preoperative radiographic findings and
loss of renal function has not been adequately investigated.
Direct measurements of glomerular filtration rate (GFR)
are uncommonly performed on partial nephrectomy patients.
Therefore, most partial nephrectomy renal function studies
rely on estimates of glomerular filtration based on serum
creatinine, such as the Modification of Diet in Renal Disease
(MDRD) or Cockroft-Gault equations. While estimates of
glomerular filtration may be adequate in most situations,
these methods may be insensitive to longitudinal changes in
renal function.15,16 To detect small but clinically important
differences in renal function, other methods of assessing
glomerular filtration, such as urine creatinine clearance, may
be necessary. The purpose of this study was to determine the
association between preoperative renal and tumour charac-
teristics and change in creatinine clearance following partial
This study was approved by the institutional review board.
Consecutive patients referred to a single urologic oncologist
(IC) at the University of Ottawa (Ottawa, Ontario, Canada)
with an enhancing renal mass between 2003 and 2008
were enrolled in this renal function study. Patients with an
organ-confined, sporadic, solitary tumour (<4 cm or <7 cm
if the patient had a GFR <60 mL/min) and normal appearing
contralateral kidney were offered an open partial nephrec-
tomy. Patients receiving renal replacement therapy were
excluded. Patients were also excluded if they had previous
renal surgery, had a solitary kidney or multiple renal tumours
at presentation (excluding renal cysts).
In all cases, the kidney was approached using a supra-
11th rib mini-flank incision. The rib was not resected.
Mannitol (12.5 g) was administered about 5 minutes prior
to renal ischemia. The hilar arteries and veins were occluded
using bulldog clamps and 10 minutes of renal hypothermia
was achieved using saline slush prior to tumour resection
The GFRs, based on creatinine clearance measurements,
were assessed preoperatively and 3, 6 and 12 months post-
operatively (GFR = [24-hour urine creatinine concentra-
tion × 24-hour urine volume] / [serum creatinine × 1440 min/
day]). The primary outcome was relative difference in GFR
([postoperative GFR − preoperative GFR] / preoperative
GRF). We previously observed that GFR remains stable
between 3 months and 12 months post-partial nephrec-
tomy;17 therefore, postoperative GFR was considered the
average of the 3 postoperative renal function assessments.
We identified, a priori, the following potential radio-
graphic predictors of change in GFR: maximal tumour
diameter, tumour location (pole or mid-pole), tumour depth
(60% within the parenchyma considered endophytic18) and
renal volume (L × W × H / 6) × π). All tumour and kidney
metrics were obtained from preoperative abdominal com-
puted tomography or magnetic resonance imaging without
knowledge of renal function outcomes.
Univariate and multivariable linear regression analyses
were performed for all predictor variables. Common vari-
ance and approximate normality assumptions were visu-
ally assessed using model residuals. All comparisons are
presented with 95% confidence intervals to assess for clini-
cally meaningful type II error. Risk of type I error was set at
5% with a p value of less than 0.05 considered statistically
Forty-nine patients received a partial nephrectomy during
the study period and 36 qualified for the study. Five patients
were excluded because they had a solitary kidney, 3 had
bilateral tumours, 3 were non-compliant with urine col-
lections and 2 were lost to follow-up. Preoperative patient
and tumour characteristics are presented in Table 1. The
contralateral kidney volume was similar to the volume of
the kidney with the tumour in most patients (contralateral
kidney volume: affected kidney volume; median 1.0; inter-
quartile range [IQR] 0.86-1.15). The median cold ischemic
time (including 10 minutes of cooling) was 37 minutes (IQR:
32-43) and average estimated blood loss was 284 ± 157 mL.
All cases had negative tumour margins and, histologically
12 (46%) were clear cell renal cell carcinoma, 9 (35%)
were papillary renal cell carcinoma, 2 (8%) were chromo-
phobe renal cell carcinoma, 2 (8%) were oncocytoma and
1 (4%) was angiomyolipoma. No patient required comple-
tion nephrectomy and no patient required renal replace-
ment therapy during the study period. At 1-year follow-up,
no patient experienced local or distant tumour recurrence.
Overall, the mean decrease in GFR was 5.7 mL/min
which corresponded to a 6.8% relative decrease in renal
function following partial nephrectomy (p < 0.01). On uni-
variate and multivariable analysis, larger kidney volume,
greater tumour diameter, endophytic tumours and tumours
located in the renal pole were associated with worse renal
function outcome (Table 2). However, the associations were
not statistically significant and only tumour depth seemed
to represent potential clinical significance.
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CUAJ • February 2011 • Volume 5, Issue 1
Partial nephrectomy renal function
As the technical and indication boundaries of partial
nephrectomy expand, cancer control and short-term com-
plication rates have been closely scrutinized.3-5,7 However,
it is unclear which patients will have the best or worst renal
function outcomes postoperatively. Many urologists may
not perform laparoscopic partial nephrectomy on large or
endophytic tumours. Therefore, some must choose between
a laparoscopic radical nephrectomy and an open partial
nephrectomy. Since a flank incision may be associated with
a more complicated and lengthy convalescence, the inher-
ent risks of open partial nephrectomy need to be carefully
balanced with potential benefits.
Traditionally, in the setting of a normal contralateral kid-
ney, radical nephrectomy was considered the best treatment
for patients with primary renal malignancy. It was believed
that maintenance of renal function was not a concern in
these patients since transplant donors do not seem to have
an increased incidence of renal failure compared to the over-
all population.19,20 However, transplant patients are highly
selected healthy individuals and patients with renal tumours
often have significant comorbid disease, which is highlighted
in recent studies that reveal higher rates of long-term renal
insufficiency and mortality in radical nephrectomy patients
compared to partial nephrectomy patients.9,12,13
In the present study, we attempted to identify preoperative
radiographic factors associated with renal function change.
Importantly, we did not identify characteristics that prohib-
ited the use of partial nephrectomy; our findings reaffirm
the effectiveness of partial nephrectomy at preserving renal
function, as average postoperative GFR was only 6.8% less
than preoperative measurements. For example, after adjust-
ing for covariates, a 1-centimeter difference in tumour size
was associated with a 0.6% decrease in renal function.
Therefore, on average, a partial nephrectomy for a 5-centi-
meter tumour results in less than a 2% predicted decrease
in renal function compared to a partial nephrectomy for a
2-centimeter tumour. Furthermore, if we consider the lower
95% confidence limit for renal size (3.9% decrease in GFR
per cm), the predicted decrease in renal function for the
above scenario would result in an 11.7% decrease in renal
function. Given that radical nephrectomy usually results in a
30% to 40% loss of estimated GFR,2,8-11 it seems that patients
functionally benefit from partial nephrectomy regardless of
The associations between change in renal function and
tumour size and location have been reported in other stud-
ies.18,21-23 In these reports, the effect of tumour diameter were
considered after adjusting for operative variables, including
ischemic time. Nevertheless, most of the model coefficients
from these studies were consistent with our findings. For
example, other authors have not observed statistical or clini-
cal differences in renal function associated with tumour size
(0.7 to 1.9 mL/min for every centimeter increase in tumour
The association between endophytic tumours and worse
postoperative renal function may be secondary to unadjust-
ed confounders, such as volume of functioning parenchyma
resected. Song and colleagues evaluated the effect of renal
volume reduction and observed the proportion of renal vol-
ume resected was the strongest predictor of change in renal
function following partial nephrectomy (0.95% decrease in
GFR for every percent decrease in renal volume; 95% CI
0.74 to 1.16).18 When the authors adjusted for potential
confounders, including warm ischemic time and percent
decrease in renal volume, the association between endo-
phytic tumours and renal function change became clini-
cally insignificant (1.49% decrease in GFR; 95% CI 1.26%
to 4.24%). To avoid incision of an endophytic tumour, it
has been our practice to incise the renal capsule at the
estimated deep perimeter of the tumour (based on preopera-
tive imaging or intra-oper-
ative ultrasound), thus,
more normal parenchy-
ma was likely excised in
these cases compared to
mesophytic or exophytic
Clearance of endog-
enous (i.e., creatinine)
or exogenous (i.e., 99mTc-
Table 1. Baseline characteristics of partial nephrectomy
Partial nephrectomy (n=36)
62 (52 - 69)
89 (35) mL/min
174 (35) cm3
171 (47) cm3
2.8 (1.4) cm
Age in years: median (IQR)
Preoperative GFR: mean (SD)
Affected kidney volume: mean (SD)
Contralateral kidney volume: mean (SD)
Tumour diameter: mean (SD)
Located in kidney pole
IQR: interquartile range; GFR: glomerular filtration rate; standard deviation.
Table 2. Effect of preoperative characteristics on change in renal function based on
univariate and multivariable analysis
Coeffecient (95% CI)
-0.75% per cm (-4.1 to 2.6)
-8.7% if endophytic (-18.2 to 0.8)
-6.2% if at pole (-15.5 to 2.9)
-1.5% per 100 cm3 (-15.2 to 12.3)
Coeffecient coeffecient (95% CI)
-0.57% per cm (-3.9 to 2.8)
-9.4% if endophytic (-19.0 to 0.3)
-6.9% if at pole (-16.2 to 2.5)
-1.1% per 100 cm3 (-14.6 to 12.3)
CI: confidence interval.
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CUAJ • February 2011 • Volume 5, Issue 1
Breau et al.
DTPA) substances are regarded as the most valid methods to
assess renal function.24 While preferred to serum creatinine
equations (i.e., Cockroft-Gault), urine clearance may also
be inaccurate if patients do not properly collect urine speci-
mens. To reduce risk and influence of error, we reinforced
proper collection methods during patient consultations
and averaged the results of 3 postoperative investigations
to determine renal function. Nonetheless, more expensive
and invasive tests, such as clearance of radioisotopes (99mTc-
DTPA, 51Cr-EDTA and 125I-iothalamate), have reduced risk of
measurement error and may be considered in future partial
While our observations are consistent with previous stud-
ies, several methodologic limitations should be considered.
All of these cases were performed using renal hypothermia
and associations may differ if warm ischemia is used. In
addition, generalizations should only be applied to patients
with comparable preoperative characteristics. Lastly, the
association between preoperative characteristics and post-
operative renal function likely fall within the confidence
intervals presented. When the confidence interval includes
clinically meaningful associations, such as the case for
tumour depth, further definitive studies are required.25
Partial nephrectomy in the setting of a functioning contralat-
eral kidney results in a small decrease in overall renal func-
tion. Compared to historical radical nephrectomy outcomes,
the preservation of renal function was favourable regardless
of tumour size and location. Partial nephrectomy should be
considered in all patients with organ confined, surgically
amenable tumours and a normal contralateral kidney.
*Department of Urology, Mayo Clinic, Rochester, MN; †Department of Surgery, Division of Urology,
Ottawa University Hospital, Ottawa, ON; ±Clinical Epidemiology Program, Ottawa Health Research
Institute, Ottawa, ON
Competing interests: None declared.
This paper has been peer-reviewed.
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Correspondence: Dr. Ilias Cagiannos, Assistant Professor, Department of Surgery, Division of Urology
The Ottawa Hospital - Civic Campus, B3 Urology, 1053 Carling Ave., Ottawa, ON K1Y 4E9; fax:
CUAJVolume5No1February2011.indd 481/31/11 3:44 PM