Prevalence of and factors associated with Na + /K + imbalances in a population of children hospitalized with febrile urinary tract infection

We aimed to assess the prevalence of and factors associated with Na + /K + imbalances in children hospitalized for febrile urinary tract infection (fUTI). This retrospective Italian multicenter study included children aged 18 years or younger (median age = 0.5 years) who were discharged with a primary diagnosis of fUTI. Na + /K + imbalances were classified as hyponatremia (sodium < 135 mEq/L), hypernatremia (sodium > 145 mEq/L), hypokalemia (potassium < 3.5 mEq/L), hyperkalemia (potassium > 5.5 mEq/L), and concurrent hyponatremia and hyperkalemia, in the absence of evidence of hemolyzed blood samples. Among the 849 enrolled children, 23% had hyponatremia, 6.4% had hyperkalemia, 2.9% had concurrent hyponatremia and hyperkalemia, 0.7% had hypokalemia, and 0.4% had hypernatremia. In the multiple logistic regression analysis, after applying the Bonferroni correction, only C-reactive protein (C-RP) levels were significantly associated with hyponatremia (OR = 1.04; 95% CI: 1.02-1.06; p < 0.001), only age was significantly associated with hyperkalemia (OR = 1.7; 95% CI: 1.1-2.7; p = 0.01), and only CAKUT was significantly associated with concurrent hyponatremia and hyperkalemia (OR = 4.3; 95% CI: 1.7-10.8; p = 0.002). Even after adjusting for the presence of kidney hypoplasia, abnormal renal echogenicity, pelvi-caliceal dilation, ureteral dilation, uroepithelial thickening of the renal pelvis, bladder abnormalities, pathogen other than E. coli, concurrent hyponatremia and hyperkalemia persisted significantly associated with CAKUT (OR = 3.6; 95% CI: 1.2-10.9; p = 0.02). Conclusion: Hyponatremia was the most common Na + /K + imbalance in children hospitalized for fUTI, followed by hyperkalemia and concurrent hyponatremia and hyperkalemia. C-RP levels were most strongly associated with hyponatremia, age with hyperkalemia, and CAKUT with concurrent hyponatremia and hyperkalemia (suggestive of transient secondary pseudo-hypoaldosteronism). Therefore, in children who develop concurrent hyponatremia and hyperkalemia during the course of a fUTI, an underlying CAKUT could be suspected.