Childhood idiopathic hypercalciuria--clinical significance of renal calyceal microlithiasis and risk of calcium nephrolithiasis.

OBJECTIVE: To evaluate the clinical significance of renal calyceal microlithiasis (RCM) in children with idiopathic hypercalciuria (IHC).

MATERIAL AND METHODS: RCM is a renal echographic finding defined as the presence of hyperechogenic spots < 3 mm in diameter in the renal calyces. These spots have been associated with the presence of nephrourological symptoms in children and are considered to represent a stage prior to urolithiasis. We reviewed the medical records of 103 children (63 girls, 40 boys; age range 1-14 years; mean age 6.57 years) referred for various complaints who had IHC. Renal echography was routinely performed. At diagnosis, 52 children had RCM, 35 showed normal echography, 14 had calculi and two presented nephrocalcinosis. A long-term follow-up study was carried out to compare the clinical manifestations, analytic data and renal echographic findings of patients with RCM and those with normal echography.

RESULTS: The clinical manifestations and the results of biochemical studies did not differ significantly between the two groups. Renal sonographic findings during the follow-up period revealed that, of patients with initial RCM, 35 showed normalized sonographic findings, two developed calculi and 36 developed recurrent RCM. Of the children with normal initial echography, 17 developed RCM and three developed calculi. The risk of developing lithiasis was less in children with RCM than in those with normal initial renal echography (0.04 vs 0.09), the relative risk being 0.45 (95% CI 0.08-2.55). The clinical and analytic differences between the group of 14 children with initial lithiasis and the other two groups previously described were also analyzed and no significant differences were found. An ongoing echographic study of these patients showed that the echograph was normalized in 10 children at some point or other, while seven developed RCM (four unilateral, three bilateral). In 13 cases the lithiasis reappeared, and the relative risk of recurrent lithiasis compared with those who initially showed no lithiasis was 16.16 (CI 95% 6.81-38.31).

CONCLUSION: Our results indicate that up to 85% of children with IHC presented RCM in follow-up sonographies. This echographic finding, which may appear and disappear at different points during follow-up, does not seem to indicate an increased risk of lithiasis.