78 Guan et al.
Investigación Clínica 63(1): 2022
calyceal stones with a diameter greater than 2
cm. The SFR was as high as 90% one month af-
ter operation. Compared with that in the PCNL
group in the same period, the SFR was as high
as 90.6% one month after operation, displaying
no statistically significant difference. Zeng et
al. 18 applied UMP to treat lower calyceal stones
with a diameter smaller than 25 mm, and the
channel size was F12-14. The SFR could reach
95.8% three months after operation, and the
incidence rate of postoperative complications,
especially the blood loss, was significantly re-
duced, suggesting that UMP has a good applica-
tion prospect in the treatment of kidney stones.
The results of this study showed that compared
with those in UMP, the average operation time
was obviously prolonged, the postoperative
hospital stay was markedly shortened, and the
total hospitalization expenses were remarkably
reduced in the RIRS group. However, the loss of
Hb after operation in the UMP group was only
(7.9±3.7) g/L due to the thinner operation
channel, which was higher than that in RIRS
group (5.0±3.4) g/L, but it notably declined in
comparison with that after PCNL (9.6 g/L on
average) reported in the literature 19, indicat-
ing that the effect of UMP in reducing blood
loss is satisfactory. In addition, there were no
statistically significant differences in the VAS
score and BCS score between the two groups of
patients 24 h after operation, and the pain did
not increase because of the puncture, implying
that UMP has a slight impact on patients due
to the small puncture channel.
The incidence rate of systemic inflam-
matory response syndromes after endoscop-
ic stone surgery was 8.6-11.4%, and without
timely treatment, the syndromes in some
patients will develop into urinary sepsis and
even cause death. It is reported that exces-
sive intrapelvic pressure [>30 mmHg (1
mmHg=0. 133 kPa)] and long accumula-
tion time (>50 s) can evidently increase the
incidence rates of postoperative fever and
urinary sepsis 20, 21. The results of this study
manifested that the postoperative fever rate
was 8.8% in the RIRS group and 5.9% in the
UMP group. Besides, the level of inflamma-
tory factors in the UMP group was also mark-
edly lower than that in the RIRS group. This
may be due to the fact that negative pres-
sure suction was utilized during UMP, which
reduced the pressure in the renal pelvis and
the risk of infection.
SFR is an important indicator for evalu-
ating the effectiveness of lithotripsy. Accord-
ing to a report, the included angle between
the infundibulum of the lower calyx and pelvis
affects the SFR of RIRS in treating lower caly-
ceal stones. The smaller the included angle
is, the lower the SFR will be 22. In the treat-
ment of lower calyceal stones using UMP, the
lower calyx can be directly punctured, thus
avoiding this effect. The results of this study
illustrated that the SFR after the first-stage
surgery in UMP group was significantly high-
er than that in RIRS group. It is believed that
if the stone hardness is high and bleeding
during operation affects the visual field, the
operation time will be too long. Besides, if
there is urinary tract infection before opera-
tion, secondary surgery or postoperative as-
sisted lithotripsy should be considered, and
the double-J stent catheter can be indwelt
after operation, which is beneficial to both
the first-stage RIRS and the postoperative
lithotripsy.
This study was a retrospective study. The
number of enrolled patients was limited, the
follow-up time was short, the follow-up con-
tent was not comprehensive, and the long-
term prognosis of patients was not analyzed.
In the future, long-term follow-up multi-cen-
ter studies with large sample sizes are needed
to verify the conclusions of this study.
As a conclusion, RIRS and UMP are
safe and effective in the treatment of 2-3 cm
lower calyceal stones. The first-stage UMP is
characterized by a high SFR, short operation
time and low postoperative infection risk,
while RIRS is featured with less blood loss
and low total expenses.