Clin Nephrol. 2020 Dec 23. doi: 10.5414/CN110229. Online ahead of print.
BACKGROUND: Febrile urinary tract infection (fUTI) can be associated with acute kidney injury (AKI). We aimed to study the risk factors for AKI, its pathophysiological categories, and the role of urinary neutrophil gelatinase-associated lipocalin (uNGAL) in differentiating these categories in patients hospitalized with fUTI.
MATERIALS AND METHODS: We prospectively studied patients with fUTI admitted to the Department of Medicine of a tertiary care hospital in southern India from January 2017 to December 2018. Clinical evaluation, renal imaging, and estimation of fractional excretion of sodium (FeNa) and uNGAL were done at baseline. AKI was defined as ≥ 0.3 mg/dL rise in serum creatinine (SCr) within 48 hours during hospital stay (KDIGO criterion) or discharge SCr value 0.5 mg/dL or less compared to peak SCr after admission.
RESULTS: We studied 100 patients. Their mean age was 52 (± 14) years; 45 were men. In all, 52 had AKI: pre-renal in 11 (21%), intrinsic renal in 24 (47%), post-renal in 16 (31%), and missing data 1 patient. uNGAL levels were significantly higher in the AKI group compared to the no-AKI group (median [IQR] 91.1 [13.2 - 188] vs. 264.9 [115.2 - 355.2] ng/mL; p < 0.001). On multivariable analysis, male sex (adjusted odds ratio, aOR [95% CI] 2.8 [1.09 - 7.14]), hypertension (4.12 [1.24 - 13.7]) and hydroureteronephrosis (7.82 [1.55 - 39.4]) were independently associated with AKI. There was an increasing trend of uNGAL across the three categories of AKI (pre-renal 106.1 [14.6 - 261.7] ng/mL, intrinsic renal 210.8 [8.5 - 353.8] ng/mL, and post-renal 335.5 [269.2 - 692.8] ng/mL; p = 0.001). Patients with pre-renal AKI had significantly lower levels of uNGAL compared to the other two categories combined (106.1 [14.6 - 261.7] vs. 284.6 [179 - 434.4] ng/mL; p = 0.016).
CONCLUSION: Hospitalized fUTI patients should be evaluated for AKI, and obstructive uropathy should be ruled out in those with AKI. uNGAL levels may help in differentiating the pre-renal type of AKI from the other two categories.