Focus on the "chicken and egg problem" - the relationship between kidney stones and recurrent urinary tract infections

The concomitant relationship between UTI and KSD has been largely proven
.
As early as 1989, Hugosson et al.
showed that the risk of
UTI could be permanently reduced by aggressive stone interventions.
A study of 1325 patients with KSD showed that after 7 years of follow-up, the positive rate of urine culture in patients with KSD was 28%, much higher than that in healthy people, and patients with UTI were more likely to undergo surgical intervention
.
The proportion of patients with KSD with UTI ranged from 18.
7% to 36%, and the risk of stone UTI varied by component, with calcium oxalate, uric acid stones, or calcium oxalate mixed with calcium phosphate and magnesium ammonium phosphate having a higher
risk of UTI.
Not only struvite, but almost all chemical components of KSD are associated
with UTI.
In addition, one retrospective study showed that the prevalence of urolithiasis was higher in UTI patients than in the general population, and the presence of urinary tract stones was associated with
poorer clinical outcomes.
This is similar to the findings of Yilmaz et al.
, which found that urinary tract stones may increase the risk of
UTI.

Recent literature has found that surgical radical treatment of KSD can help reduce the bacterial burden and thus achieve the effect
of treating rUTI and/or bacteriuria.
The link between the two is significantly related
regardless of the type of surgery ureteroscopic lithotomy (URS), percutaneous nephrolithotriptomy (PCNL), or extracorporeal shock wave lithotripsy (ESWL).

Table 1 KSD intervention modalities and UTI results

The results of a prospective cohort study in the UK showed that stone clearance (SFR) and infection clearance (IFR) at 3, 6, and 12 months postoperative in patients treated with URS were 96% vs 88%, 90% vs 86%, and 82% vs 71% (P<0.
001<b10>), respectively, indicating a strong association between SFR and IFR.
Agarwal et al.
believe that the only significant difference between patients with KSD who develop rUTI and those who do not after surgical intervention is the presence of residual stones
.
Recurrence of postoperative urinary tract infection is associated with stone recurrence, but it is important to note that rUTI is also associated with
other risk factors such as indwelling catheters or intermittent catheterization, diabetes, hypertension, etc.

With the development of in vitro studies, the latest evidence suggests that bacterial strains may play an important role
in the formation and growth of KSD.
For example, struvite formation is associated with Proteus, Staphylococcus, Pseudomonas, Providencia, Klebsiella, and Serratia, while stones other than struvite infection are mainly induced
by Escherichia coli and enterococci.
These findings help to elucidate the pathogenesis of KSD and provide reference for its prevention and treatment
.

The study shows that UTI and KSD coexist with each other and are causal to
each other.
Patients with KSD should be advised to aggressively control infection by stone removal, particularly if
the patient has a recurrent UTI or has other risk factors not related to the chemical composition of the stone.
To prevent further onset of UTI, stone cultures can be obtained if available to allow effective, targeted antibiotic therapy
.

References:

Ripa F, Pietropaolo A, Montanari E, Hameed BMZ, Gauhar V, Somani BK.
Association of Kidney Stones and Recurrent UTIs: the Chicken and Egg Situation.
A Systematic Review of Literature.
Curr Urol Rep.
2022 Sep; 23(9):165-174.
doi: 10.
1007/s11934-022-01103-y.
Epub 2022 Jul 25.
PMID: 35877059; PMCID: PMC9492590.