Role of urinary supersaturation in the evaluation of children with urolithiasis.
Timed urine collections are a standard part of the evaluation for predisposition to stone formation in children with urolithiasis. Supersaturation is defined as the ratio of the concentration of dissolved salt to its solubility in urine. The purpose of the present study was to determine if adding supersaturation to the standard timed urine collection increased the ability to detect a metabolic predisposition to stone formation. Thirty-two children with urolithiasis had 24-hour urine measurements of calcium, oxalate, citrate, uric acid, and cystine (the "traditional" evaluation), as well as supersaturation for calcium oxalate, calcium phosphate, and uric acid, on the same urine sample. Nine (28%) of the 32 were hypercalciuric, 2 (6%) hyperoxaluric, and 4 (12%) hypocitraturic. In total, 14 (44%) had a metabolic predisposition that was detected by the traditional evaluation. Supersaturation was elevated in 18 (56%), including nine who did not have metabolic predisposition detected by traditional evaluation. Urine volume was low in 17 (53%) of 32 children, including eight of nine children with abnormal supersaturation but normal traditional evaluation. Only one child with normal traditional evaluation and normal urine volume had elevated supersaturation. These results show that the benefit of adding supersaturation to the traditional evaluation was largely negated by consideration of urine volume.
Lande
Marc B
MB
Division of Pediatric Nephrology, Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642, USA. marc_lande@urmc.rochester.edu
Varade
William
W
Erkan
Elif
E
Niederbracht
Yvonne
Y
Schwartz
George J
GJ
D000293:Adolescent; D002118:Calcium / Q000652:urine; D002648:Child; D002675:Child, Preschool; D019343:Citric Acid / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010070:Oxalates / Q000652:urine; D014527:Uric Acid / Q000652:urine; D014545:Urinary Calculi / Q000175:diagnosis* / Q000652:urine*
D010070:Oxalates; D014527:Uric Acid; D019343:Citric Acid; D002118:Calcium
Adv Pediatr. 1993;40:353-84
8249711
J Urol. 1997 Aug;158(2):557-9
9224359
Mayo Clin Proc. 1993 Mar;68(3):241-8
8474265
Clin Pediatr (Phila). 1998 Oct;37(10):583-99
9793728
Pediatr Nephrol. 2004 May;19(5):516-20
15015063
Endocrinol Metab Clin North Am. 2002 Dec;31(4):1001-15, ix
12474642
J Urol. 2001 Oct;166(4):1247-51
11547051
J Urol. 1985 Dec;134(6):1242-4
3840540
J Urol. 1999 Apr;161(4):1077-81
10081841
J Urol. 1983 Jun;129(6):1166-8
6854792
J Urol. 1989 Apr;141(4):918-20
2926890
Am J Clin Nutr. 2002 Mar;75(3):561-9
11864864
J Urol. 2002 Dec;168(6):2568-71
12441985