The momentum of kidney stone patient “expulsion” from the emergency department has never been greater. Big stone? No problem. Obstruction? No problem. Infection? That’s the problem. Some of these patients may require admission.

A recent interesting malpractice claims trend has prompted a reassessment of outpatient management of nephrolithiasis. Females with an active ureteral stone with obstruction and, most important, possible urinary tract infection (UTI) have returned with pyelonephritis and sepsis, suffering horrific outcomes. Urinary symptoms, other than those associated with acute ureterolithiasis, are often absent in these patients.

Although few recommendations deserve inclusion of an “always” or a “never,” this trend at least deserves some consideration in our approach to certain cases.

In England and Wales, 91 percent of deaths from nephrolithiasis were associated with kidney and ureteral stones, compared to lower tract stones, which accounted for 7.9 percent of deaths. Although the raw numbers aren’t alarming—mean 9.4 deaths per year from ureteric stones (141 deaths total) and 130.³ deaths per year from urolithiasis (1,954 deaths total) identified between 1999 and 2013—their report of increasing trends in developed nations is concerning. Although men had a higher incidence (1.3:1) of stones compared to women, mortality was significantly higher in females (1.5:1). Equally worrisome, urosepsis accounts for 25 percent of adult sepsis cases.¹

“This too shall pass,” a quote dating back to 1839, fits well with regard to stone size.²

It has been taught that stones ≥5 mm are unlikely to pass spontaneously. That’s a reasonable guideline, but what difference does it really make? If patients are pain-free or their pain can be controlled with oral analgesics, there are no indications for admission (eg, pyelonephritis, solitary kidney, etc.), and follow-up is available, then size isn’t critical for the disposition decision. Jendeberg et al reported multiple CT-related variables that may predict stone passage.³ Although limited by the study’s retrospective design and nonstandardized follow-up, their conclusion suggests our 5 mm line in the sand is less than clear. “The spontaneous passage rate in 20 weeks was 312 out of 392 stones, 98% in 0–2 mm, 98% in 3 mm, 81% in 4 mm, 65% in 5 mm, 33% in 6 mm and 9% in ≥6.5 mm wide stones.”³ Stone size appears to be relegated to an academic discussion with limited relevance to emergency medicine.

Hydronephrosis is practically synonymous with obstruction and is expected with active ureteral stones. However, an active stone that is unlikely to pass may prolong the duration of associated ureteral obstruction.³ In the context of possible infection, obstruction is important.

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.