Correspondence: Ronald J Hogg MD, Baylor University Medical Center, 3500 Gaston Avenue, Dallas, Texas 75246, USA.

¹Southwest Pediatric Nephrology Study Group (Central Office: Baylor University Medical Center, 3500 Gaston Avenue, Dallas, TX 75246). Director: RONALD J. HOGG. Statistician: JOAN S. REISCH. Administrative Assistant: KAYE GREEN. SPNSG Centers and individuals participating in this study: Baylor College of Medicine, Houston, Texas: PHILIP L. BERRY, L. LEIGHTON HILL, SAMI A. SANJAD; Baylor University Medical Center, Dallas, Texas: RONALD J. HOGG, KAYE GREEN; Tulane University Medical Center, New Orleans, Louisiana: FRANK BOINEAU, JOHN E. LEWY, RADHAKRISHNA BALIGA; University of Arkansas for Medical Sciences, Little Rock, Arkansas: WATSON ARNOLD, EILEEN ELLIS; University of Colorado Health Science Center, Denver, Colorado: GARY M. LUM, DOUGLAS M. FORD; University of Oklahoma Medical Center, Oklahoma City, Oklahoma: JAMES WENZL; University of Tennessee, Memphis, Tennessee: F. BRUDER STAPLETON, SHANE ROY III, ROBERT J WYATT; University of Texas Southwestern Medical Center, Dallas, Texas: BILLY S. ARANT, JR., MICHEL BAUM, JOAN REISCH; University of Texas Health Science Center at Houston, Texas: SUSAN B. CONLEY, GILBERT ROSE; University of Texas Health Science Center at San Antonio, San Antonio, Texas: MICHAEL FOULDS, SUDESH MAKKER; University of Texas Medical Branch, Galveston, Texas: BEN H. BROUHARD, ALOK KALIA, LUTHER B. TRAVIS; University of Utah Medical Center, Salt Lake City, Utah: EILEEN BREWER, RICHARD SIEGLER.

Received 20 April 1989; Revised 17 August 1989; Accepted 23 August 1989.

Abstract

Idiopathic hypercalciuria: Association with isolated hematuria and risk for urolithiasis in children. A prospective multicenter study was designed to determine the frequency and prognostic importance of hypercalciuria in children with hematuria. Urinary calcium excretion was examined in 215 patients with unexplained isolated hematuria (no proteinuria, urolithiasis, infection or systemic disorder). Hypercalciuria (urinary calcium excretion > 4 mg/kg/day) was identified in 76 patients (35%). Compared to patients with normal urinary calcium excretion, children with hematuria and hypercalciuria were characterized by male preponderance, white race, family history of urolithiasis, gross hematuria and calcium oxalate crystals. Renal biopsies were performed in 10 patients with urinary calcium excretion 0.4 to 2.5 mg/kg/day; three had IgA glomerulonephritis, three had glomerular basement membrane thinning, one had proliferative glomerulonephritis and three were normal. Renal biopsies in three patients with hypercalciuria showed focal segmental glomerulosclerosis, hereditary nephritis or no abnormalities. Oral calcium loading tests showed renal hypercalciuria in 26 patients, absorptive hypercalciuria in 15 patients and were not diagnostic in 35 patients. Serum parathyroid hormone, bicarbonate and phosphorus and urinary cyclic adenosine monophosphate concentrations were similar in the three groups of hypercalciuric patients. Urinary calcium excretion after one week of dietary calcium restriction was higher (5.8 mg/kg/day) in renal hypercalciuria than in other hypercalciuric patients (3.4 mg/kg/day), P < 0.01. One to four years follow-up was available for 184 patients. Eight of 60 hypercalciuric patients developed urolithiasis or renal colic compared to 2 of 124 patients with normal urinary calcium excretion (P < 0.001). Hypercalciuria is commonly associated with isolated hematuria and represents a risk factor for future urolithiasis in children with hematuria. Oral calcium loading tests offer little diagnostic benefit over 24-hour urinary calcium excretion following dietary calcium restriction.