Is there a connection between urinary tract infections (UTIs) and hypokalemia?

Although we don’t usually think of UTIs being associated with electrolyte abnormalities, there seems to be a connection between UTI—particularly pyelonephritis—and hypokalemia in adults, possibly related to the impairment of renal potassium resorption due to tubular injury.1

A 2020 study of over 80,000 hospitalized patient found a significantly higher rate of hypokalemia (10%) in patients with UTI (identified based on ICD9 codes) vs non-UTI patients (4%, O.R. 2.3, 95% C.I. 2.2-2.4). This association was independent of patients’ comorbidities and medications. Among patients with UTI, recurrent UTI was associated with hypokalemia (O.R. 1.1, 95% C.I. 1.1-1.2). Unfortunately, no attempt was made to distinguish cystitis from pyelonephritis. The authors reported that in “several patients”, the urinary potassium secretion was increased.  

The association between pyelonephritis and hypokalemia was first reported back in the 1950s and was initially referred to as “potassium losing nephropathy”. 2 It turns out that some of these cases might have had underlying primary hyperaldosteronism (Conn’s) and perhaps pyelonephritis unmasked this condition.  Later, cases of urinary potassium wasting with probable pyelonephritis in the absence of excessive aldosterone excretion were also reported, with resolution of potassium wasting with treatment of the infection in some instances.3,4  

So it looks like the association between pyelonephritis and hypokalemia may be real! Next time you see hypokalemia in a patient with pyelonephritis, don’t be surprised! The corollary: watch for hypokalemia in your patient with pyelonephritis!

Bonus Pearl: Did you know that prevention of potassium loss with spironolactone treatment in pyelonephritis has been reported, suggesting a possible role for aldosterone despite lack of hyperaldosteronism.3

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References

  1. Shen AL, Lin HL, Lin HC, et al. Urinary tract infection is associated with hypokalemia: a case control study. BMC Urology 2020;20:108. Urinary tract infection is associated with hypokalemia: a case control study | BMC Urology | Full Text (biomedcentral.com)
  2. Eastham RD, McElligott M. Potassium-losing pyelonephritis. BMJ 1956; :898-89. Potassium-losing pyelonephritis. – Abstract – Europe PMC
  3. Gerstein AR, Franklin SS, Kleeman CR, et al. Potassium losing pyelonephritis:response to spironolactone. Arch Intern Med 1969;123:55-57. Potassium Losing Pyelonephritis: Response to Spironolactone | JAMA Internal Medicine | JAMA Network
  4. Jones NF, Cantab MB, Mills IH, et al. Reversible renal potassium loss with urinary tract infection. Am J Med 1964;37:305-310. REVERSIBLE RENAL POTASSIUM LOSS WITH URINARY TRACT INFECTION – PubMed (nih.gov)

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University,their affiliate healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

Is there a connection between urinary tract infections (UTIs) and hypokalemia?

Could my patient with acute dysuria and less than 10,000 E. coli/ml on urine culture still have a urinary tract infection (UTI)?

Absolutely! Although historically ≥100,000 bacteria/ml has been used as a criterion for UTI based on studies of women with pyelonephritis in the 1950s,1 several studies have since found that this criterion may not be met in up to 50% of symptomatic patients with UTI. 2-6 A lower criterion of 100-1,000 bacteria/ml of urine increases the sensitivity of urine culture to ~90% or more for diagnosis of UTI (albeit with lower specificity). 2-5

A 1982 NEJM study involving UTIs due to coliforms in acutely dysuric women found that the traditional count of ≥100,000 bacteria/ml in midstream urine missed ~50% of cases based on positive bladder cultures. 2 Similarly a 2013 NEJM study reported that 40% of women with symptomatic UTI would be missed if the ≥100,000 bacteria/ml criterion for midstream urine is used. 3

Among symptomatic men, 32% have been found to have <100,000 bacteria/ml in their midstream urine 4 and a single urine specimen by urethral catheterization growing ≥ 100 bacteria/ml is consistent with bacteriuria for both men and women. 5

Since most of these studies have involved UTI caused by E. coli or other coliforms, more data are needed to find out if the same findings apply to non-coliform urinary pathogens.

Bonus Pearl: Did you know that because quantitative urine culture results are concentration dependent (ie, “per ml”), a dilute urine—as may be found in patients experiencing diuresis—will result in lower numbers of bacteria/ ml. 5

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 References

  1. Kass EH. Asymptomatic infections of the urinary tract. Trans Assoc Am Physicians 1958;69:56-74. https://pubmed.ncbi.nlm.nih.gov/13380946/
  2. Stamm WE, Counts GW, Running KR, et al. Diagnosis of coliform infection in acutely dysuric women. N Engl J Med 1982;307:463-8. https://pubmed.ncbi.nlm.nih.gov/7099208/
  3. Hooten TM, Roberts PL, Cox ME, et al. Voided midstream urine culture and acute cystitis in premenopausal women. N Engl J Med 2013;369:1883-91. https://www.nejm.org/doi/full/10.1056/NEJMoa1302186
  4. Lipsky BA, Ireton RC, Fihn SD, et al. Diagnosis of bacteriuria in men: specimen collection and culture interpretation. J Infect Dis 1987;155:847-54. https://pubmed.ncbi.nlm.nih.gov/3559288/
  5. Nicolle LE, Bradley S, Colgan R, et al. Infectious Diseases Society of America Guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clin Infect Dis 2005;40:643-54. https://pubmed.ncbi.nlm.nih.gov/15714408/
  6. Roberts KB, Wald ER. The diagnosis of UTI: colony count criteria revisited. Pediatrics 2018;141:e20173239. https://doi.org/10.1542/peds.2017-3239

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Could my patient with acute dysuria and less than 10,000 E. coli/ml on urine culture still have a urinary tract infection (UTI)?

How long should I treat my patient with urinary tract infection and E. Coli bacteremia?

Although traditionally 7 to 14 days of antibiotic therapy has been recommended for Gram-negative bacteremia, more recent studies suggest that shorter antibiotic treatment courses are as effective as longer treatments for a variety of infections, particuarly those due to Enterobacteriaceae (eg, E. Coli, Klebsiella sp) in patients with low severity illness (1). 

Keep in mind that short course therapy may not apply to all patients with UTI and bacteremia, such as those with prostatitis (not included in the most recent study [1,2]), which requires longer course of antibiotics (3)

 
A 2019 randomized-controlled study involving primarily patients with bacteremia caused by E. Coli or Klebsiella sp. (~75%) with most cases associated with UTI (~70%) found that 7 days was as effective as 14 days of treatment in hemodynamically stable patients who are afebrile for at least 48 hours without an ongoing focus of infection (1). More specifically, there was no significant difference between the 2 groups in the rates of relapse of bacteremia or mortality at 14 or 28 days.

 
An accompanying editorial concluded that “7 days of treatment may be sufficient for hospitalized, non-critically ill patients with Gram-negative bacteremia and with signs of early response to treatment” (4)  Again, the accent should be on hemodynamically stable patients who respond rapidly to treatment. 

 
Bonus Pearl: While on the subject of shorter course antibiotic therapy, a 2016 “mantra” article nicely summarizes more recent suggestions for common infectious disease conditions (5). Obviously, clinical judgment should be exercised in all cases.
• Community-acquired pneumonia                               3-5 days (vs 7-10 days)
• Nosocomial pneumonia                                                 8 days or less (vs 10-15 days)
• Pyelonephritis                                                                  5-7 days (vs 10-14 days)
• Intraabdominal infection                                             4 days (vs 10 days)
• COPD acute exacerbation                                             5 days or less (vs >6 days)
• Acute bacterial sinusitis                                               5 days (vs 10 days)
• Cellulitis                                                                            5-6 days (vs 10 days)

 

 

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References
1. Yahav D, Franceschini E, Koppel F, et al. Seven versus 14 days of antibiotic therapy for uncomplicated Gram-negative bacteremia: A noninferiority randomized controlled trial. Clin Infect Dis 2019; 69:1091-8. https://academic.oup.com/cid/article/69/7/1091/5237874       2. Yahav D, Mussini C, Leibovici L, et al. Reply to “Should we treat bacteremic prostatitis for 7 days”.  Clin Infect Dis 2010;70:751-3. DOI:10:1093/cid/ciz393.

3.  De Greef J, Doyen L, Hnrard S, et al. Should we treat bacteremic prostatitis for 7 days? Clin Infect Dis 2020;70:351https://academic.oup.com/cid/article-abstract/70/2/351/5488067?redirectedFrom=fulltext
4. Daneman D, Fowler RA. Shortening antibiotic treatment durations for bacteremia. Clin Infect Dis 2019;69:1099-1100. https://academic.oup.com/cid/article-abstract/69/7/1099/5237877?redirectedFrom=fulltext
5. Spellberg B. The new antibiotic mantra: “ Shorter is better”. JAMA Intern Med 2016;176:1254-55. https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/2536180

How long should I treat my patient with urinary tract infection and E. Coli bacteremia?

Should I consider fosfomycin in the treatment of urinary tract infection in my male patient with suspected prostatitis?

Although fosfomycin (FM) has been approved by the FDA only for the treatment of uncomplicated urinary tract infection (UTI) in women, it may also have a role in the treatment of acute and chronic prostatitis among males given its favorable levels in the prostate tissue. 1-5

Despite lack of studies comparing the efficacy of FM with that of commonly used antibiotics for treatment of prostatitis, the potential utility of FM is supported by several reports of its efficacy in the treatment of prostatitis, including those caused by extended-spectrum beta-lactamase (ESBL)-producing gram-negative rods. 1,4-5

When considering FM for treatment of prostatitis, a higher dose than customary may be needed (3 g once daily, not every 48-72 h) . 4 Although the optimal duration of therapy with FM is unclear in this setting, 12-16 weeks of therapy was used in 2 patients with recurrent UTIs and prostatitis due to multi-drug resistant ESBL-positive E. coli. 4

Given its pharmacokinetics and lack of proven efficacy, avoid FM in pyelonephritis, perinephric abscess or UTI with bacteremia. 2

References

  1. Falagas ME, Vouloumanou EK, Samonis G, et al. Fosfomycin. Clin Microbiol Rev 2016;29:321-347. https://www.ncbi.nlm.nih.gov/pubmed/26960938
  2. Wankum M, Koutsari C, Gens K. Fosfomycin use. Pharmacy Times. November 30, 2017. https://www.pharmacytimes.com/publications/health-system-edition/2017/november2017/fosfomycin-use
  3. Cunha BA, Gran A, Raza M. Persistent extended-spectrum β-lactamase-positive Escherechia coli chronic prostatitis successfully treated with a combination of fosfomycin and doxycycline. International J Antimicrob Agents 2015;45:427-29. https://www.ncbi.nlm.nih.gov/pubmed/25662814
  4. Grayson ML, Macesic N, Trevillyan J, et al. Fosfomycin for treatment of prostatitis: new tricks for old dogs. Clin Infect Dis 2015;61:1141-3. https://www.ncbi.nlm.nih.gov/pubmed/26063723
  5. Falagas ME, Rafailidis PI. Fosfomycin: the current status of the drug. Clin Infect Dis 2015;61:1144-6. https://www.ncbi.nlm.nih.gov/pubmed/26063717
Should I consider fosfomycin in the treatment of urinary tract infection in my male patient with suspected prostatitis?

My patient with pyelonephritis has positive blood cultures for E. coli? Should I order repeat blood cultures to make sure the bacteremia is clearing?

Although a common practice, follow-up blood cultures (FUBCs) may not be necessary in otherwise clinically stable or improving patients with aerobic gram-negative bacteremia. This is probably due to the often-transient nature of gram-negative bloodstream infections  and less propensity of these organisms to cause intravascular infections (eg, endocarditis) compared to gram-positives. 1

A 2017 study addressing the value of FUBCs in gram-negative bacteremia found that repeat positive blood cultures were uncommon with positive results not associated with mortality or higher ICU admissions. 1 Specifically, 17 FUBCs had to be drawn to yield 1 positive result.  Although the numbers of positive FUBCs were too low for in-depth analysis, it was concluded that FUBCs added little value in the management of gram-negative bacteremias.

In contrast, FUBCs are recommended in the following situations: 1-3

  • Staphylocccus aureus bacteremia given the propensity of this organism to cause intravascular (eg, endocarditis) and metastatic infections.
  • Presumed or documented endocarditis or intravascular device infections (eg, intravenous catheters and pacemakers) to document timely clearance of bacteremia
  • Infections involving organisms that may be difficult to clear such as fungemia or multi-drug resistant pathogens.

As with many things in medicine, clinical context is important before ordering tests and blood cultures are no different. The urge to order FUBCs should also be balanced with the possibility of having to deal with  contaminants. 

References

  1. Canzoneri CN, Akhavan BJ, Tosur Z et al. Follow-up blood cultures in gram-negative bacteremia: Are they needed? Clin Infect Dis 2017;65:1776-9. https://www.ncbi.nlm.nih.gov/pubmed/29020307
  2. Tabriz MS, Riederer K, Baran J, et al. Repeating blood cultures during hospital stay: Practice pattern at a teaching hospital and a proposal for guidelines. Clin Microbiol Infect 2004;10:624-27. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1469-0691.2004.00893.x
  3. Mylotte JM, Tayara A. Blood cultures: Clinical aspects and controversies. Eur J Clin Microbiol Infect Dis 200;19:157-63. https://www.ncbi.nlm.nih.gov/pubmed/10795587

 

 

My patient with pyelonephritis has positive blood cultures for E. coli? Should I order repeat blood cultures to make sure the bacteremia is clearing?

Can I rely on the physical exam to rule out symptomatic urinary tract infection (UTI) in my hospitalized patient?

Suprapubic tenderness, costovertebral angle tenderness (CVAT) and fever seem to be more helpful in ruling in than ruling out infection. And, before you hang your hat on the available data, remember that most of the studies involve women with uncomplicated UTI in primary care or emergency department settings, not our older hospitalized patients at risk of complicated infections.  With these caveats in mind….

Suprapubic tenderness has been reported in only about 15-20% of women with acute cystitis. 1

CVAT has been associated with symptomatic UTI but with only a weakly positive LR (1.7, 1.1-2.5), and an insignificant negative LR. 2  In a single center study involving hospitalized patients (mean age 53 y), CVAT was either absent or “obscure” in about 10% of patients with acute pyelonephritis on CT.3

Fever was associated with a positive likelihood ratio (1.6, 1.0-2.6) by 1 systematic study 2 but not another, 4 with insignificant negative LR in both. Fever was also absent in about 10% of hospitalized patients with pyelonephritis in the single center study above.3

So, when evaluating a patient with possible symptomatic UTI (particularly cystitis), the presence of physical exam findings  may be more helpful than their absence.

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References

  1. Kurowski K. The woman with dysuria. Am Fam Physician 1998, 57:2155-2164. https://www.aafp.org/afp/1998/0501/p2155.html
  2. Bent S, Nallamothu BK, Simel DL, et al. Does this woman have an acute uncomplicated urinary tract infection? JAMA 2002;287:2701-2710. https://www.ncbi.nlm.nih.gov/pubmed/12020306
  3. Lee Y-J, Cho S, Kim SR. Unilateral and bilateral acute pyelonephritis: differences in clinical presentation, progress and outcome. Postgrad Med 2014;90:80-85. https://www.ncbi.nlm.nih.gov/pubmed/24255118
  4. Median-Bombardo D, Jover-Palmer A. Does clinical examination aid in the diagnosis of urinary tract infections in women? A systematic review and meta-analysis. BMC Family Practice 2011;12:111. https://bmcfampract.biomedcentral.com/articles/10.1186/1471-2296-12-111

 

Can I rely on the physical exam to rule out symptomatic urinary tract infection (UTI) in my hospitalized patient?