Discussion
PBUC analysis is a standard procedure before any stone surgery. PBUC is
very important for selecting patients undergoing f-URS to receive
prophylaxis and for predicting the risk of postoperative infection
complications [1,5]. In a previous meta-analysis, a single
preoperative antibiotic dose was shown to reduce postoperative pyuria
and bacteriuria, but it did not statistically significantly reduce
postoperative urinary tract infections [18]. Theoretically, the
effect of PAP is considered to prevent the spread of bacteria during the
stone operation; however, the actual efficacy of this application
remains uncertain. In our study, PBUC growth was present in 19.4% of
the patients. Although there was no growth in the post-treatment control
cultures of these patients, it was observed that bacteriuria persisted
in RPUC in 27.1%. In light of this information, it is necessary to
establish a proper prophylaxis and treatment strategy in patients with a
positive PBUC to prevent infectious complications. The AUA guidelines
recommend PAP to all patients to reduce urosepsis after f-URS while EAU
states that PAP is indicated only for those with a high risk of
infection [8-10].
In another previous study, the efficacy of PAP and preoperative
antimicrobial treatment was compared using the cultures taken
intraoperatively, and growth was found in intraoperative cultures in
only 3.2% of the patients who were negative for PBUC and given PAP. In
the same study, 43.3% of the cultures taken intraoperatively from
patients with a positive PBUC had growth despite appropriate
antibiotherapy. That study demonstrated the efficacy of preoperative
antimicrobial therapy to be 71.6% [19]. In other words, despite
preoperative antimicrobial therapy, 43.3% of the patients had growth in
any of the intraoperative cultures taken during surgery; i.e., an
existing or different microorganism managed to survive [19].
He et al. administered cefuroxime PAP for three days preoperatively to
patients without preoperative urine culture growth and observed reduced
growth in RPUC. The authors emphasized that preoperative antibiotic
administration should be adjusted according to the risk level and
suggested that RPUC showed better bacterial colonization [20]. In
our study, we determined that even if the patients with a positive PBUC
before the operation were treated, some had growth in RPUC. However,
PBUC positivity is not an independent predictive factor for the
possibility of growth in RPUC. The efficacy of PAP or antimicrobial
treatment before surgery is limited against bacteria that we were not
able to detect preoperatively. Therefore, we consider that even if PBUC
is negative in patients scheduled to undergo f-URS, we should be
prepared for the possibility of a positive RPUC in some patients to
ensure that appropriate antibiotherapy is started promptly to prevent
alarming complications, such as sepsis.
In the literature, it has been reported that there is significant growth
in intraoperative cultures in patients with renal stones and a history
of obstructive pyelonephritis [19]. In our study, a statistically
significant relationship was found between stone localization and
presence of hydronephrosis and RPUC positivity. If a stone is in a
location that can cause hydronephrosis (e.g., pelvis and proximal
ureter), it can explain a higher rate of growth in RPUC. In patients
with urinary system obstruction, infection or bacterial colonization in
the upper urinary tract may continue even in the presence of a negative
PBUC. Other studies have revealed that in addition to the degree of
hydronephrosis, the thickness of the ureteral wall surrounding the stone
may also increase. A significant association between ureteral wall
thickness (UWT) and degree of obstruction has been demonstrated, and a
possible predictive value has been presented [21,22]. Sarica et al.
found the cut-off value of UWT as 3.35 mm and they were not able to
place a double-J stent in patients with a value over this threshold
[15]. The authors considered that if the guidewire required for the
double-J insertion could not reach the proximal of the stone, the urine
sample obtained preoperatively would also not be sufficient for the
culture analysis. Impacted stones have indirect NCCT findings, including
changes in UWT, degree of hydronephrosis, and fluid collection around
the kidney [23]. Another study revealed that the thickness of the
wall immediately surrounding the stone depends on the elapsed time and
the degree of inflammatory reactions that occur [24].In our study,
the wall tissue thickness at the proximal ureter and pelvis was higher
in patients with RPUC growth. However, due to being a confounding factor
in the multivariate analysis, it was not included in the model.
In the literature, it was shown that 10.1% of the patients with a
negative PBUC were positive for RPUC, but these patients also did not
show any signs of infection [4]. Preoperative NCCT findings are
important for this patient group. It has been previously emphasized that
RPUC can be predicted using certain non-specific findings, such as the
thickening of the renal pelvis and stranding of perirenal fat renal in
pyelonephritis [25]. Basmacı et al. reported that at a cut-off value
of 0, renal pelvis HU had 100% sensitivity and 96% specificity for a
positive RPUC[14]. In our study, the HU value was found to be lower
in the RPUC group. We certainly do not claim that it is possible to
definitively determine the presence of RPUC growth by examining HU.
However, we consider that in patients examined for stone disease and
planned to undergo f-URS, pelvis HU can predict RPUC growth, and thus
help identify those that require wider-spectrum PAP and a more close
follow-up in the postoperative period. A low HU value in patients with
RPUC growth may be due to bacterial burden colonizing in that location,
fragmented urine, and/or increased urine density.