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The incidence of urolithiasis in infants is unknown. The aim of this study was to investigate clinical characteristics, nutrition, calcium, phosphate, 25-hydroxyvitamin D (25(OH)D), alkaline phosphate, and parathyroid hormone in infants with urolithiasis. There were 32 infants (23 boys and 9 girls) of the mean age of 6.4 ± 3.7 months (range 2-12 months), with diagnosis of urolithiasis enrolled into the study. Boys were younger than girls (5.3 vs. 9.1 months, respectively; p < 0.05). The infants were receiving prophylactic vitamin D 3 . Twenty-one of them were fed with milk formula, 9 were breastfed, and 2 were on a mixed diet. The major clinical symptoms consisted of irritability in 19 (59%) and urinary tract infection in 6 (19%) infants. Hypercalcemia and hyperphosphatemia were detected in the serum in 30 (94%) and 19 (60%) infants, respectively. The serum calcium level was higher in boys than girls (10.8 vs. 9.8 mg/dL, respectively; p < 0.05). Four (12.5%) infants had increased activity of alkaline phosphatase. The serum level of 25(OH)D was high in 3 (9%), low in 2 (6%), and normal in 27 (85%) infants. Parathyroid hormone was low in eight (25%) infants. Hypercalciuria and hyperphosphaturia were found in 11 (34%) boys and 8 (25%) girls. Family history of urolithiasis was positive in eight (25%) infants. We conclude that urolithiasis occurs in infancy more often in boys fed with milk formula and in those who received vitamin D supplementation. Hypercalcemia, hyperphosphatemia, and hypercalciuria are the most common changes present in clinical metabolic tests.

Early diagnosis of urinary tract infection (UTI) is challenging in infants due to unspecific symptoms, difficulty in urine collection and possible contamination. The aim of this study was to assesses the usefulness of serum and urine neutrophil gelatinase-associated lipocalin (sNGAL and uNGAL, respectively) in the diagnosis of febrile and non-febrile UTI in infants. This prospective observational study enrolled 66 infants with the first episode of UTI and 18 healthy controls. At the time of enrollment, sNGAL, uNGAL, urinalysis, urine culture, white blood cell count (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), procalcitonin (PCT), and serum creatinine (sCr) were assessed. We found that, on average, both sNGAL and uNGAL levels were significantly higher in febrile UTI, compared to non-febrile UTI and controls. In turn, the mean sNGAL level, but not uNGAL, was significantly higher in the non-febrile UTI group compared to controls. sNGAL positively correlated with WBC, CRP, ESR and PCT, and uNGAL with CRP and leukocyturia. The receiver operating curves (ROC) demonstrate that the optimum cut-off of 76.2 ng/ml for sNGAL (sensitivity 92.9%, specificity 94.4%, and the area under the curve (AUC) of 0.98) and of 42.2 ng/ml for uNGAL (sensitivity 73.8%, specificity 72.2%, and AUC of 0.76) for diagnosing febrile UTI and 39.0 ng/ml for sNGAL (sensitivity 83.3%, specificity 55.6%, and AUC of 0.70) for diagnosing non-febrile UTI. In conclusion, serum NGAL is an excellent marker for the early diagnosis of febrile UTI, with sensitivity and specificity higher than those of urine NGAL. Diagnostic sensitivity of serum NGAL is smaller in non-febrile infants suffering from UTI, and urine NGAL is not useful for this purpose at all.