Idiopathic hypercalciuria of childhood: 4-to 11-year outcome

Apart from a minority with urolithiasis, the majority of children diagnosed with idiopathic hypercalciuria present with macro- or microhematuria, abdo minal or back pain, or voiding symptoms. With dietary and pharmacological i nterventions, most such children become asymptomatic and are lost to follow -up, hence their long-term outcome is unclear. In the present study, we eva luated the status of 14 males and 19 females aged 8-17 years (mean 11.9 yea rs, median 11.2 years) 4-11 years (mean 6.9 pears, median 6.5 years) after the initial diagnosis of idiopathic hypercalciuria not associated with urol ithiasis. A questionnaire was answered and two random urine samples provide d 3-4 weeks apart were analyzed for calcium (Ca), sodium (Na), potassium (K ), and creatinine (Cr). Urine Ca/Cr ratio greater than or equal to 0.21 (mg /mg) was defined as hypercalciuria. At the time of the study none were unde r follow-up, although 7 children were still exhibiting voiding symptoms. No child developed clinical urolithiasis. Based on the first urine specimen, 16 of the 33 (48.4%) were hypercalciuric. Their 2nd urinalysis showed persi stent hypercalciuria in 8 and normocalciuria in 8. Urine Na/K ratio (mEq/mE q) decreased in the latter 8 from 5.08+/-2.67 to 3.03+/-2.23 (P<0.05). Of t he 17 initially nonnocalciuric children, 5 did not submit a 2nd specimen, 1 1 remained normocalciuric, and 1 became hypercalciuric with an increase in urine Na/K ratio. Twenty-three children (all 8 persistently and 9 intermitt ently hypercalciuric plus 6 normocalciuric) were studied by ultrasonography . Only in 1 asymptomatic persistently hypercalciuric child was a single sma ll renal calcification noted. Introduction of a low-Na/high-K diet in 7 per sistently hypercalciuric children resulted in a decrease in UNa/K ratio fro m 7.34+/-2.15 to 4.14+/-3.09 (P<0.01) and UCa/Cr ratio from 0.25+/-0.04 to 0.13+/-0.03 (P<0.01). We conclude that even though over time most hypercalc iuric children become asymptomatic, many remain hypercalciuric. Further fol low-up is required to ascertain whether these children are at risk of devel oping kidney stones. If they are at risk then long-term compliance with a l ow-Na/high-K diet might be beneficial, as it can normalize calciuria in the majority of these children.