title: Cystatin C as a marker of early renal insufficiency in children with congenital neuropathic bladder.
abstract: OBJECTIVE
  Due to decreased muscle mass in children with congenital neuropathic bladder there may be significant inaccuracy when using the creatinine based estimated glomerular filtration rate. Cystatin C is highly sensitive and specific for measuring changes in the glomerular filtration rate in children and in patients with muscle wasting conditions. We hypothesized that a cystatin C calculated glomerular filtration rate would be more sensitive than the standard creatinine based modified Schwartz equation to detect renal insufficiency in children with congenital neuropathic bladder.
  
  
  METHODS
  We prospectively identified children with congenital neuropathic bladder at a multidisciplinary spina bifida clinic who underwent serum creatinine and serum cystatin C testing. Clinical history and anthropomorphic variables at the time of laboratory testing were catalogued. The creatinine based glomerular filtration rate was estimated using the modified (bedside) Schwartz formula and the cystatin C based rate was calculated using the Zappitelli cystatin C formula.
  
  
  RESULTS
  Dual estimated glomerular filtration rate calculation was done in 69 children at a total of 74 patient encounters. Absolute creatinine was within age range normal limits in each patient, including 1 with chronic kidney disease stage 3A. The median creatinine based estimated glomerular filtration rate was 123 ml per minute/1.73 m(2) (range 58 to 229). The median cystatin C based estimated rate was 103 ml per minute/1.73 m(2) (range 47 to 144) for an absolute median rate reduction of 15.4%. Using cystatin C estimates chronic kidney disease stage was upgraded from stage 1 to 2 in 13 patients (18.8%).
  
  
  CONCLUSIONS
  In children with neuropathic bladder the cystatin C estimated glomerular filtration rate is a better screening test for early renal insufficiency that is not detected by creatinine based rate calculations. To our knowledge it remains to be determined whether the cystatin C estimated glomerular filtration rate can ultimately improve the clinical outcome in this population.
authors.affiliation: Division of Pediatric Urology, Department of Urology, Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; Naval Medical Center Portsmouth, Portsmouth, Virginia.
authors.forename: Janelle A
authors.initials: JA
authors.lastname: Fox
authors.affiliation: Division of Pediatric Urology, Department of Urology, Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Anne G
authors.initials: AG
authors.lastname: Dudley
authors.affiliation: Department of Nephrology, Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors.forename: Carlton
authors.initials: C
authors.lastname: Bates
authors.affiliation: Division of Pediatric Urology, Department of Urology, Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. Electronic address: cannongm2@upmc.edu.
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Cannon
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D011446:Prospective Studies; D051437:Renal Insufficiency / Q000175:diagnosis*; D012307:Risk Factors; D001750:Urinary Bladder, Neurogenic / Q000150:complications* / Q000151:congenital
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine
keywords: creatinine; cystatin C; glomerular filtration rate; kidney; neurogenic; urinary bladder