Nephrolithiasis during the first 6 months of life in exclusively breastfed infants.

BACKGROUND We investigated etiology and prognosis of infantile nephrolithiasis, including whether lithogenic and anti-lithogenic content of breast milk affects its formation. METHODS Thirty infants with nephrolithiasis and 30 healthy infants exclusively breastfed for the first 6 months of life were included in this prospective cohort case-control study. At entry, age, sex, and timing of birth of patients and controls were recorded. All patients were diagnosed and followed up periodically using ultrasonography. All infants received oral vitamin D (400 units/day). Lithogenic (calcium, oxalate, uric acid, phosphate) and anti-lithogenic (citrate, magnesium) components of maternal milk, serum calcium, phosphate, magnesium, 25-hydroxy vitamin D and parathormone, as well as spot urine calcium, uric acid, cystine, oxalate, magnesium, citrate/creatinine ratio, and calcium/citrate ratio were compared. RESULTS Mean follow-up period was 56.1 ± 6.8 months. There was no difference concerning lithogenic and anti-lithogenic content of breast milk. Serum calcium, phosphorus, alkaline phosphatase, and 25-hydroxy vitamin D levels (49.1 ± 19 vs. 26.7 ± 4 ng/ml, p < 0.001) were significantly higher and parathormone level significantly lower in patients. Random urine calcium/creatinine and calcium/citrate ratios were significantly higher in patient group (0.63 ± 0.40 vs. 0.42 ± 0.10 and 0.62 ± 0.12 vs. 0.41 ± 0.25 mg/mg, respectively, p < 0.01). Three patients were lost to follow-up after the first year. At last follow-up, calculi disappeared in 25/27 remaining patients without interventions or therapy. CONCLUSIONS Breast milk does not have an etiologic effect in infantile nephrolithiasis. Higher serum vitamin D levels may have roles in development of lower levels of PTH and higher levels of serum and urine calcium, leading to stone formation. The prognosis for infantile stones is excellent. Graphical abstract.