Uncomplicated UTIs can almost universally be treated without hospitalization. UTIs in the context of nephrolithiasis with obstruction, however, are complicated. Appropriate diagnosis is critical.

Although admission may be unnecessary, noting the potential for poor outcomes, even with a seemingly benign presentation, mandates something more than the standard approach for those without possible UTI. Thus, initiation of antimicrobials, phone consultation, confirmed close follow-up, and, in some cases, admission, are all reasonable considerations.

The limitations of nitrite, leukocyte esterase, and the presence white blood cells (>5/hpf) via dipstick or formal urinalysis may lead to dismissing positive findings. In asymptomatic patients without a stone, a wait-and-see approach is appropriate for nondefinitive findings. However, with an obstructive stone, any one being positive should prompt recognition in the medical record, the ordering of a culture, and consideration of the above strategies.
Watch the pH. Some organisms are urease-producing, reducing urea, which has an antibacterial effect, and will increase ammonia levels.⁴ This effect has been found in more than 200 bacterial species, including Ureaplasma urealyticum, Proteus, Klebsiella, and Pseudomonas.⁴ The alkaline environment prompts formation of struvite-magnesium ammonium phosphate (infected stones) and apatite-calcium phosphate stones.^5,6 Also, staghorn calculi are frequently composed of these two types.⁷ UTI may be causative, not an incidental finding, with nephrolithiasis.^5,6,7 Further, some suggest greater mortality from struvite and staghorn stones, as they cannot be treated with antimicrobials alone.⁶
Being mindful of possible infection associated with acute nephrolithiasis may improve outcomes and will definitely reduce your professional liability risk.

References

1. Kum F, Mahmalji W, Hale J, et al. Do stones still kill? An analysis of death from stone disease 1999-2013 in England and Wales. BJU Int. 2016;118(1):140-144.
2. Keyes R. The Quote Verifier: Who Said What, Where, and When. New York, NY: St. Martin’s Press; 2006:159-160.
3. Jendeberg J, Geijer H, Alshamari M, et al. Size matters: the width and location of a ureteral stone accurately predict the chance of spontaneous passage. Eur Radiol. 2017;27(11):4775-4785.
4. McLean, Nickel JC, Cheng KJ, et al. The ecology and pathogenicity of urease-producing bacteria in the urinary tract. Crit Rev Microbiol. 1988;16(1):37-79.
5. McLean, Nickel JC, Noakes VC, et al. An in vitro ultrastructural study of infectious kidney stone genesis. Infect Immun. 1985;49(3):805-811.
6. Nickel JC, Costerton JW, McLean RJ, et al. Bacterial biofilms: influence on the pathogenesis, diagnosis and treatment of urinary tract infections. J Antimicrob Chemother. 1994;33(Suppl A):31-41.
7. Zhao P. Staghorn calculi in a woman with recurrent urinary tract infections: NYU case of the month, December 2016. Rev Urol. 2016;18(4):237-238.