Aim: We aimed to examine whether there is any association between serum levels of 25-hydroxyvitamin D [25(OH)D₃] and urinary tract infection (UTI) among children. Methods: White blood cell count, serum C-reactive protein, calcium, phosphorus, alkaline phosphatase, parathormone, and serum 25(OH)D₃ levels were measured in 82 children experiencing a first episode of UTI, with no risk factors for UTI, and 64 healthy control children. Results: The mean serum levels of 25(OH)D₃ among children with UTI were significantly lower than those of controls (11.7 ± 3.3 vs. 27.6 ± 4.7 ng/ml; p < 0.001). The serum levels of 25(OH)D₃ were significantly lower in patients with acute pyelonephritis compared to patients with lower UTI (8.6 ± 2.8 vs. 14.2 ± 3.0 ng/ml; p < 0.001). Within the study group, mean serum levels of 25(OH)D₃ among girls were lower than those of boys (10.9 ± 3.4 ng/ml vs. 13.2 ± 4.4 ng/ml; p < 0.001). Multivariate analysis showed that a serum 25(OH)D₃ level of <20 ng/ml (odds ratio 3.503, 95% confidence interval 1.621-7.571; p = 0.001) was associated with UTI in children. Conclusions: Our results suggest that vitamin D deficiency may be a risk factor for UTI in children.

The MPV is a fast and reliable measurement with considerable predictive value for the diagnosis of APN and renal scars, and its predictive capacity is better than that of CRP, ESR, and WBC values.

There is high antibiotic resistance in children with UTI. The patterns of uropathogen antimicrobial resistance vary in susceptibility to antimicrobials depending on region and time. Thus, the trends of antibiotic susceptibility patterns should be analyzed periodically to select the appropriate regimen for UTI treatment.

There is a need for extended studies with a larger number of patients from specific groups to better understand the reactivation frequency and identify risk factors. EBV and CMV reactivation should be taken into consideration in critically ill patients with fever, without specific symptoms and unresponsive to the treatment.

Low vitamin D is associated with rotaviral diarrhea. This is the first study in the literature to show this, and this result needs to be repeated in larger controlled clinical studies.