RESULTS
In this prospectively conducted study, no difference was observed
between the groups in terms of the mean age, female/male ratio, BMI,
presence of DM and stone locations. However, the mean stone dimensions
were calculated as 343.65±236.63 mm2and 122.48±51.292
mm2for the PNL and RIRS groups, respectively,
indicating a statistically significant difference (p ≤ 0.001) (Table1).
The mean operation time of the patients was 60.25 ± 22.98 and 47.50 ±
20.69 minutes in the PNL and RIRS groups, respectively, and a
statistically significant difference was found between the two groups (p
≤ 0.001). The mean length of hospital stay was 4.10 ± 2.37 days in the
PNL arm and 1.53 ± 1.61 days in the RIRS arm, also indicating a
statistically significant difference (p ≤ 0.001). Stone-free status and
presence of CIRFs were accepted as surgical success, and there was no
statistically significant difference between the two groups in terms of
this outcome. The modified Clavien classification was used for the
postoperative complication evaluation. Twenty-six patients (65%) that
had undergone RIRS were evaluated as Clavien 0, 12 (30%) patients as
Clavien 1, and 2 (5%) patients as Clavien 2 (infection) (22.5%). In
the PNL group, Clavien 0 was seen in 9 (22.5%) patients, Clavien 2 in 6
(22.5%) (infection in 4, bleeding in 1, and arteriovenouz fistula in
1), and Clavien 3A in 1 (2.5%) (double-J stent requirement). There was
a statistically significant different between the two groups in terms of
the Clavien classification (p=0.001) (Table1).
Preoperative hemoglobin, urea, creatinine, GFR, MIOX and KIM-1 levels,
no significant difference was observed between two groups.In the PNL
arm, the post-operative hemoglobin (12.92 ± 1.37g/dl) was found to be
statistically significantly lower than in the RIRS arm (14.98 ± 3.30
g/dl) (p ≤ 0.001) (Table 2).
In the intra-group comparisons, there was no statistically significant
difference between the preoperative and postoperative values of
hemoglobin urea, creatinine, GFR and KIM-1 in patients that had
undergone RIRS; however, the mean MIOX value was increased from 17.80 ±
15.39 ng/ml preoperatively to 25.30 ± 20.11 ng/ml postoperative, and
this increase was statistically significant (p = 0.001) (Table 2).Within
the PNL group, the hemoglobin value was measured as 14.01 ± 1.34 mg/dl
preoperatively and 12.92 ± 1.37 mg/dl postoperatively, indicating a
statistically significant difference (p ≤ 0.001). Similarly, in this
group, the preoperative and postoperative KIM-1 values were 1.21 ±
0.44 and 1.68 ± 0.58 ng/ml,respectively, and the preoperative and
postoperative MIOX values were 15.23±9.36 ng/ml and 25.81±16.13 ng/ml,
respectively showing a statistically significant difference (p ≤0.001
for both). No significant difference was observed in terms of the other
variables (Table 2). In the intra-group evaluation for the
postoperative and preoperative differences, the mean MIOX increase was
calculated as 7.501 ± 16.46 ng/ml for the RIRS group and 10.583 ± 9.73
ng/ml in the PNL group, and there a statistically significant difference
between the two groups in favor of the latter (p = 0.001). Similarly,
while the mean KIM-1 increase was 0.375 ± 1.13 ng/ml in the RIRS group,
it was 0.471 ± 0.328 ng/ml in the PNL group, indicating a statistically
significant difference (p = 0.003) (Table 2).
DISCUSSION
Urinary system stone disease is a pathology that constitutes an
important part of urology practice. The treatment of kidney stone
disease has changed significantly, especially in the last two decades,
with the improvement of tools and reduction in their size due to the
development of technology. ESWL, PNL and RIRS are considered as three
main treatment methods for the treatment of upper urinary stone disease
[13].
PNL is recommended as the preferred minimally invasive method due to its
high success rates in patients with a high stone burden
(>20mm) and complex stones [5]. However, complications,
such as hemodynamic impairment, vascular bleeding, and parenchymal
bleeding, and acute kidney injury may occur after the operation
[14].In recent years, with the technological advances in
endourological equipment and increasing surgeon experience, RIRS
presents as an alternative to PNL, with lower complication rates [15;
16]. There are publications that consider RIRS to be a very good
minimally invasive treatment alternative for intrarenal stones of
<20 mm and report high stone-free rates even in larger stone
sizes [17; 18].
During surgical operations for kidney stones, there may be certain
damage to the kidneys. Having knowledge of the extent of injury caused
by each technique used can guide surgeons in the selection of both
patients and surgical techniques. Creatinine is used in daily practice
to show kidney injury. However, creatinine is a non-specific marker
affected by various factors, including age, gender, muscle density, and
liver function. In addition, creatinine levels increase days after
kidney damage occurs by which time 50% or more of renal function is
lost [19]. Therefore, new molecules have been used to reveal kidney
injury more specifically at an earlier stage. In an experimental animal
model investigating one of these molecules, KIM-1, the urine and plasma
levels were measured after inducing ischemic kidney injury. It was found
that the plasma KIM-1significantly increased at the third hour compared
to the preoperative levels and remained at a high level until the
96th hour [20]. In the same study, it was shown
that the plasma KIM-1 level was correlated with urine the KIM-1 level
and significantly higher in individuals with kidney injury compared to
healthy individuals. Many studies have evaluated urine KIM-1 levels;
however, to the best of our knowledge, there is no study in the
literature investigating the role of plasma KIM-1 molecule in revealing
possible damage of kidney stone surgery.
In a previous study, the diagnostic sensitivity and specificity of the
MIOX molecule released from the proximal tubules of kidneys in showing
acute kidney injury were observed as 53.8% and 81.5%, respectively.
Accordingly, it was concluded that MIOX could be used as a marker of
acute kidney injury [21]. In addition, when compared to creatinine,
MIOX was observed to increase much earlier in case of kidney injury
[21].However, a review of the literature shows no study comparing
the MIOX molecule in patients that have undergone PNL and RIRS.
In our study, the stone volume of the PNL group was statistically
significantly higher than that of the RIRS group (p <0.001).
This difference was due to the indication of PNL for stones with a
larger volume, as recommended in the EAU 2019 urinary system stone
disease guidelines. In addition, the operation time was significantly
longer in the PNL group (60.25 ± 22.98 min) compared to the RIRS group
(47.50 ± 20.69 min) (p ≤ 0.001). We also consider this to be related to
the different stone volumes. Similarly, in other studies comparing PNL
and RIRS, the stone volume was observed to be higher and the operation
time was longer operation times in the former [13; 22]. However, in
a study in which the stone sizes were similar in the two surgery groups,
the RIRS duration was found to be longer in lower pole stones [23].
The main reason for the prolongation of this period may be due to the
more difficult manipulation of the flexible ureteroscope in lower pole
stones. In our study, the length of hospital stay was 4.10 ± 2.37 days
in the PNL group and 1.53 ± 1.61 days in the RIRS group, indicating a
statistically significantly longer value for the former (p ≤ 000.1),
which is consistent with the literature [13; 22; 23].
In this study, the operative success rates were 92.5% and 90% in the
PNL and RIRS arms, respectively, and no statistical difference was
observed between them. The success rates of the studies in the
literature were also similar. However, the postoperative stone-free
rates are affected by clinical parameters, such as stone location,
obesity, stone size, stone composition and anatomy of the renal calyces.
There are studies reporting 77% to>90% success rates in
RIRS whereas for PNL, the success rates for lower pole stones of 1-2 cm
and above 2 cm are given as 92% and 86%, respectively [25]. While
two studies [26; 27] showed a higher stone-free rate in the PNL
group (92 and 98%, respectively) than the RIRS group (89 and 95%,
respectively), another study showed a statistically non-significant
higher stone-free rate in the RIRS group compared to the PNL group
[28]. Lastly, Mehmet et al. determined the stone-free rates as
91.4% and 87% in the PNL and RIRS groups, respectively [13].
We used the modified Clavien classification to evaluate the
complications and found the rate of complications to be statistically
significantly higher in the PNL arm (p = 0.001). Similar to our results,
the literature contains studies indicating a higher rate of
complications in the PNL arm than in the RIRS arm [23; 28]. While no
major complications were observed in our study, 2 (5%) patients in the
PNL arm required blood transfusion. Post-operative fever occurred in 7
patients (17.5%) in the PNL arm and 2 (5%) patients in the RIRS arm.
In a review reported the most common complications of PNL as
extravasation (7.2%), bleeding requiring blood transfusion (11.2 -
17.5%), and fever (21 - 32.1%) while rare major complications included
septicemia (0.3 - 4.7%), colon injury (0.2 - 4.8%), and pleural injury
(0 - 3.1%) (24).
In our study, while there was no difference between the preoperative and
postoperative hemoglobin values in the RIRS arm, the postoperative
hemoglobin was statistically significant lower compared to the
preoperative value in the PNL arm (p ≤ 0.001). GyooHwan Jung et al.
reported similar data to our results.
In a previous study conducted with RIRS patients, it was observed that
MIOX did not increase in the postoperative period [29]. In contrast,
the postoperative values of the MIOX molecule statistically
significantly increased in our PNL group. The preoperative and
postoperative MIOX levels in the RIRS arm were 17.80 ± 15.3 and 25.30 ±
20.11ng/ml, respectively, and we found a statistically significant
increase in this parameter (p = 0.001). However, the increase in the
MIOX values was 10.583 ± 9.73ng/ml in the PNL group versus 7.501 ±
16.46ng/ml in the RIRS arm, indicating a statistically significantly
higher increase in the former (p = 0.001) (Table 2).
In this study, although there was an increase in the plasma KIM-1 levels
in the RIRS arm in the postoperative period, no statistically
significant difference was observed. However, the postoperative KIM-1
value in the PNL arm was found to be statistically significantly higher
than the preoperative value. Our findings our supported by Balasar et
al.[30], who compared PNL, RIRS and mini-PNL, and found an increase
in the KIM-1/creatinine values in the PNL and RIRS arms in the
postoperative period, and this increase was statistically significantly
higher in the PNL group.
We detected a statistically significant increase in both the KIM-1 and
MIOX values in the postoperative period among the patients that had
undergone PNL. In the RIRS group, this increase was observed only in
MIOX. We showed that acute kidney injury occurred in both surgical
methods; however, it was greater in PNL.
Limitations
The limitations of this study include the relatively low number of the
patients in our sample and a single blood sample collection in the
postoperative period.
CONCLUSION
In the comparison of the patients that underwent PNL or RIRS, we first
demonstrated that acute kidney injury could be detected using the MIOX
and plasma KIM-1 molecules, and the increase in these molecules was
higher in the PNL arm. The higher increase in the PNL arm suggests that
this method causes greater acute kidney injury than RIRS; however, there
is a need for further studies with larger case series to support our
data.
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