Infection stones including struvite (ammonium magnesium phosphate), apatite (calcium phosphate subtype), and the rare newberyite are often, but not always, associated with struvite stones. These stones are known to cause recurrent urinary tract infections (recUTIs) and were generally thought to form staghorn stones. Traditional thinking was that infection stones would only cause pyelonephritis and only if they were large staghorn calculi. Complete removal of these infection stones is advocated to prevent further recurrence of both stones and urinary tract infections (UTIs); thus, percutaneous nephrolithotomy (PCNL) has typically been the advocated treatment for their management. Only recently have we understood that other types of stones may also cause infections.¹

Managing the patient with recUTIs in the setting of non-obstructing renal calculi has been a continuing challenge for urologists. Historically, lower urinary tract cystitis (recUTI) was not thought to be associated with small upper tract stones. However, smaller, non-staghorn, non-infection stones have lately been associated with recUTIs. The role of removing these stones in the treatment of recUTIs has been examined in recent years.

Early work investigating the impact of kidney stone extraction on recUTIs was performed by Omar et al in 2015. In a retrospective study of 120 patients with recUTIs who underwent extracorporeal shock-wave lithotripsy (SWL), ureteroscopy (URS), or PCNL, 48% were infection-free 1 year postoperatively.² Agarwal et al subsequently examined 46 patients who underwent URS with or without PCNL in patients with recUTIs and found that stone removal led to elimination of recUTIs in 89.1% of the patients.³ In this retrospective study, patients with residual fragments were found more likely to have a recurrence of infections.³ Oliver et al prospectively studied 103 patients with recUTIs undergoing URS and found that 88% were infection-free at 3 months and 71% were at 12 months.⁴ They similarly found that patients with residual stone burden were more likely to have recurrence of their infections. In a systematic review, Ripa et al found that in 3 of the 4 studies evaluated, the majority of patients were infection-free after complete stone clearance.⁵ They concluded that the current data support performing stone extraction to reduce recUTIs regardless of the composition of stones.

These data will likely affect ongoing practice, such that urologists may consider the importance of treatment for non-obstructing stones in patients with recUTIs, as well as the need to ensure that patients are stone-free postoperatively. However, many questions persist with respect to the general treatment of patients with kidney stones and recUTIs. How should we manage these patients long term? In all studies published to date, there remain some patients who continue to experience infection after stone removal. What treatment plan should be pursued in the management of this subpopulation of patients? How do we address those patients whose infections persist? Should there be a more multidisciplinary approach to such patients involving infectious disease doctors? What, in fact, should the role of our infectious disease colleagues be in patients with nephrolithiasis and recUTIs? What is the role of small punctate stones, and do they play any role in the development of UTIs? The role of next-generation sequencing in diagnosing UTIs is the next frontier and may help us in treating our patients.

We will further explore the management of these patients in our upcoming AUA 2023 presentation of Second Opinion Cases: Recurrent UTI and the Role of Stone Removal.