Etiology of nephrocalcinosis in infants and Children

ABSTRACT

Nephrocalcinosis [NC] is the deposition of calcium and oxalate or phosphate in the renal tubules, tubular epithelium or renal interstitial tissue. It is being recognized more frequently since the introduction of ultra sonographic imaging. The sonographic appearance of NC is characterized by presence of echo- dense deposits in renal medulla, cortex or both. This study was conducted to define the underlying etiology of NC in Egyptian infants and children. Thirty two cases with NC were studied in Alexandria University Children's Hospital during the period [January 2001 to January 2004]. The ages of studied cases varied between I month and 9 years with male to female ratio of 131. Mean age at diagnosis was 2.8 +/- 2.7 years. Thorough clinical, imaging and metabolic evaluations were done to all cases. Sonographic evidences of bilateral medullary NC were evident in 87.5% of cases, combined medullary and cortical NC occurred in 9.4 % of cases, while cortical NC was found in only one case [3.13%]. Abdominal X-ray detected NC in only 34.4% of patients. Clinical presentations of NC were polyuria, polydipsia or dehydration in 62.5%, metabolic acidosis in 53%, urinary tract infection in 47%, psychomotor retardation [44%] failure to thrive [37.5%], abdominal or loin pain [31%], gross or microscopic hematuria [25%] and spontaneous passage of stones [12.5%]. Nephrolithiasis was associated with NC in 79% of the cases. Family history of renal stones was reported in 25% of cases compared to 10% in controls. , , Infants with NC [group I] had normal anion gap [AG], increased mean serum levels of calcium [Ca] and I chloride and decreased mean level of blood pH but without reaching statistical significance. Serum ; potassium, HCO3, urinary specific gravity [SG], citrate/creatinine and magnesium/ creatinine ratios were significantly reduced in group I, while urinary pH and Calcreatinine ratio were significantly elevated [p= 0.02,0.001 respectively]. Infant mortality was 41.2% due to recurrent sepsis. Blood urea, creatinine [Cr] and AG were high in patients older than one year of age [groups II and III], while HCO3 and Cr clearance were significantly lower than the control values [p<0.005]. Serum uric acid in cases older than 5 years [group III] was significantly higher than the control group. Urinary 24 hour calcium and oxalate output were significantly high in groups II and III [p=0.0001, 0.02 respectively] while urinary output of citrate, magnesium and phosphate were significantly lower in these cases compared to controls [p<0.005]. , Nephrocalcinosis was due to metabolic diseases in 75% of the cases and due to iatrogenic hypervitaminosis D [HVD] in 25%. Metabolic errors were distal renal tubular acidosis [RTA-I] in 37.5%, renal idiopathic hypercalciuria [IHC] in 25% and primary hyperoxaluria [PHyOx] in 12.5%. Hypercalciuria ' was the commonest urinary abnormality detected in 87.5% of cases, being due to RTA-I in 42%, IHC in I 29% and HVD in 29%. Hyperoxaluria was present in 723% of cases due to PHyOx. Hypocitraturia and hypomagnesuria were found in 75% and 66%of cases respectively. Etiology of NC in infants was RTA-I in 64.7% and HVD in 35.3%. The commonest cause sf NC in cases > 1 year of age was IHC [53%]. None of the studied cases showed resolution of NC during the years of follow-up [1.8 +/- 0.9 years]