The role of urinary chloride concentrations in the determination of kidney injury in children.

Background: Early stages of chronic kidney disease (CKD) are usually asymptomatic, but kidney damage that starts in childhood may persist until adulthood and can lead to serious morbidity and mortality in the following years. Therefore, preventive practices that can slow the progression of kidney damage are strongly needed. In this study, we evaluated the relationship of urinary chloride concentrations and fractional excretion of chloride (FeCl) with proteinuria and estimated glomerular filtration rate (eGFR).

Methods: This study is a retrospective descriptive study. Patients were divided into subgroups based on eGFR values and proteinuria status. It was investigated whether there was a difference between the groups in terms of urine chloride and FeCI levels.

Results: A total of 176 patients with a mean age of 11.5 ± 5.0 (2-18) years were included in the study. The most common primary diagnosis was CAKUT (n = 56, 31.8%), followed by glomerular diseases (n = 45, 25.5%). The number of patients with eGFR <90 mL/min/1.73 m² was 20 (11.4%). Urinary chloride levels were significantly lower in patients with proteinuria compared to those without (95.5 ± 74.8 mEq/L vs. 146.7 ± 85.7 mEq/L, p < 0.001). Regression analysis showed that higher chloride and FeCI levels were associated with less proteinuria. Urinary chloride was lower in stage 3 CKD compared to stage 2 (34.20 ± 20.2 mEq/L vs. 70.9 ± 60.5 mEq/L, p = 0.087), while FeCI was higher in patients with decreased eGFR (1.73 ± 0.91%, p < 0.001).

Conclusion: Strategies towards increasing urinary chloride excretion may help to slow the progression of CKD by providing a renoprotective effect via tubuloglomerular feedback (TGF), which inhibits the increase in glomerular pressure.