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)

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