title: Idiopathic hypercalciuria of childhood: 4- to 11-year outcome.
abstract: Apart from a minority with urolithiasis, the majority of children diagnosed with idiopathic hypercalciuria present with macro- or microhematuria, abdominal or back pain, or voiding symptoms. With dietary and pharmacological interventions, most such children become asymptomatic and are lost to follow-up, hence their long-term outcome is unclear. In the present study, we evaluated the status of 14 males and 19 females aged 8-17 years (mean 11.9 years, median 11.2 years) 4-11 years (mean 6.9 years, median 6.5 years) after the initial diagnosis of idiopathic hypercalciuria not associated with urolithiasis. A questionnaire was answered and two random urine samples provided 3-4 weeks apart were analyzed for calcium (Ca), sodium (Na), potassium (K), and creatinine (Cr). Urine Ca/Cr ratio > or =20.21 (mg/mg) was defined as hypercalciuria. At the time of the study none were under 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 persistent hypercalciuria in 8 and normocalciuria in 8. Urine Na/K ratio (mEq/mEq) decreased in the latter 8 from 5.08+/-2.67 to 3.03+/-2.23 (P<0.05). Of the 17 initially normocalciuric children, 5 did not submit a 2nd specimen, 11 remained normocalciuric, and 1 became hypercalciuric with an increase in urine Na/K ratio. Twenty-three children (all 8 persistently and 9 intermittently hypercalciuric plus 6 normocalciuric) were studied by ultrasonography. Only in 1 asymptomatic persistently hypercalciuric child was a single small renal calcification noted. Introduction of a low-Na/high-K diet in 7 persistently hypercalciuric children resulted in a decrease in UNa/K ratio from 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 hypercalciuric children become asymptomatic, many remain hypercalciuric. Further follow-up is required to ascertain whether these children are at risk of developing kidney stones. If they are at risk then long-term compliance with a low-Na/high-K diet might be beneficial, as it can normalize calciuria in the majority of these children.
authors.affiliation: Section of Pediatric Nephrology, The Children's Mercy Hospital, University of Missouri at Kansas City, 64108, USA. ualon@cmh.edu
authors.forename: U S
authors.initials: US
authors.lastname: Alon
authors.forename: A
authors.initials: A
authors.lastname: Berenbom
mesh_terms: D000293:Adolescent; D002118:Calcium / Q000652:urine*; D002648:Child; D003404:Creatinine / Q000652:urine; D004039:Diet, Sodium-Restricted; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D009318:Natriuresis; D011188:Potassium / Q000652:urine; D017419:Potassium, Dietary / Q000008:administration & dosage; D014463:Ultrasonography; D014545:Urinary Calculi / Q000209:etiology / Q000517:prevention & control
chemical_list: D017419:Potassium, Dietary; D003404:Creatinine; D011188:Potassium; D002118:Calcium