ELEVATED CYSTATIN C GFR IN CHILDREN WITH ANORECTAL MALFORMATIONS: DOES IT INDICATE NEPHROPATHY?
Nathalie Kremer, MD, Brian VanderBrink, MD, Pramod Reddy, MD, Eugene Minevich, MD, FACS, FAAP, Elizabeth Jackson, MD, Curtis Sheldon, MD, Marion Schulte, RN, William R. DeFoor, MD, MPH.
Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
BACKGROUND:Serum Cystatin C is becoming more widely utilized to estimate glomerular filtration rate (GFR) in complex pediatric urology patients with neurogenic bladder. An elevated GFR has been suggested to indicate possible hyperfiltration injury to the kidneys. Our protocol for follow-up has been to check a yearly GFR in patients with a diagnosis of neurogenic bladder secondary to anorectal malformations and screen for proteinuria in those with an elevated Cystatin C GFR. The purpose of this study is to assess the risk of proteinuria in this group of patients and to determine if suboptimal bladder management may be contributing to ongoing renal injury.
METHODS:This retrospective single-center cohort study included all patients with an anorectal malformation seen for neurogenic bladder between 2010 and 2015. Data collected included patient demographics, upper and lower tract imaging studies, urodynamic data, medications, Cystatin C GFR values, urine protein and creatinine data. A Cystatin C GFR of greater than 130 ml/min was considered elevated. Proteinuria was defined as a quantitative random urine protein to creatinine ratio exceeding 0.21 or presence of greater than trace protein on urinalysis. Patients with a specific urine gravity less than 1.010 were excluded.
RESULTS:A total of 103 patients were seen for evaluation of neurogenic bladder secondary to anorectal malformation. 79% were female. Median age was 10 years. 25 patients (22%) had a GFR greater than 130 ml/min. Of those, 20 patients (80%) had a negative quantitative protein to creatinine ratio and/or a negative protein level on urinalysis. A total of five patients (20%) had proteinuria. Four performed CIC via a Mitrofanoff and one had a vesicostomy. Two patients had recently undergone continent lower urinary tract reconstruction. One patient with a solitary kidney was found to be non-adherent with CIC. Proteinuria resolved in one patient within one year after continent reconstruction. In all the other patients proteinuria persisted, with confirmed proteinuria via 24 hour collection in one patient. Medical management was maximized in one patient with cloacal malformation who subsequently underwent Mitrofanoff appendico-vesicostomy due to difficulty with her native urethral access. Her GFR increased from 150 to 177 over two years with persistent proteinuria. Of the five patients with proteinuria, two had vesicoureteral reflux (one grade I and one grade III). One patient was taking an ACE inhibitor for congenital heart disease. None of the patients were found to have uninhibited detrusor contractions on filling cystometrogram. All five patients were on anti-cholinergic medication. The prevalence of proteinuria was similar between those with a normal and an elevated GFR.
CONCLUSIONS:Our findings show that an elevated Cystatin C GFR is not uncommon in patients with anorectal malformation. The majority of these patients do not have evidence of proteinuria upon screening. Suboptimal bladder management may be a cause of progressive nephropathy in these high risk children. Further follow-up is needed to understand the clinical significance of an elevated GFR in this setting to detect those at highest risk for progression of chronic kidney disease.
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