ntroduction and Objectives: To perform
external validation of S.T.O.N.E Nephrolithometry
as an emerging surgical scoring
system of patients undergoing percutaneous
nephrolithotomy (PCNL).
Materials and Methods: All PCNL cases
performed by a single endourologist (SA) from
2009 till 2013 at McGill University Health
Center were reviewed. Out of 185 cases, 155
were chosen in this study after exclusion of 2nd
look PCNL cases and cases where the percutaneous
access was established by interventional
radiologist. CT scans of these patients were reviewed
for the five parameters of the S.T.O.N.E
Nephrolithometry scoring system (stone size,
tract length, obstruction, number of involved
calyces and the stone essence). The score was
then calculated and correlated with the stone
free status (as the main goal of PCNL), in addition
to the estimated blood loss (EBL), operative
time and the length of hospital stay (LOS).
Results: A total of 155 cases were included.
The mean age was 54.9±1.2 (17-85), with 100
(64.5%) males and 55 (35.5%) females. The
mean stone score was 7.67±0.1 (5-13), with
mean stone volume of 609.8±48.4 (25-4030)
mm2, mean Hounsfield unit of 887.7±25.3
(222-1766), mean tract length of 97.3±1.9
(53-175), mean BMI of 26.9±0.5 (17.2-51),
mean operative time of 100.1±2.8 (60-240)
min and mean LOS of 4.2±0.3 (1-18). The
overall stone free rate after the primary procedure
was 71.6%. The S.T.O.N.E score significantly
affected the stone-free status (p=0.008)
and the EBL (p=0.003). There was good correlation
between the S.T.O.N.E Nephrolithometry
score and operative time (r=0.4; p=0.00)
and LOS (r=0.3; p=0.001). Therefore, the
higher the S.T.O.N.E Nephrolithometry score,
the longer the operative time, the higher the
estimated blood loss, the longer the LOS, and
the lower the stone-free status.
Conclusion: This study confirms external
validation of the S.T.O.N.E Nephrolithometry
scoring system as a preoperative predictor of
PCNL outcome. |
