Estimating Glomerular Filtration Rate in Pediatric Patients with Neurogenic Bladder: a comparison between Creatinine- and Cystatine C-equations

Abstract Purpose: Patients with neurogenic bladder (NB) have higher risk of developing chronic kidney disease (CKD). Due to their lower muscle mass, the estimated glomerular filtration rate (eGFR) using creatinine (Cr) may be overestimated and delay the diagnosis of renal failure. The study compare eGFR calculated by different formulas based on creatinine and/or cystatin C (CysC) in children with NB, and the differences between patients with lower muscle mass (underdeveloped lower limbs) and with independent gait (less muscle depletion). Methods: The eGFR was calculated in all pediatric patients with NB and CKD stage 1 and 2, using different formulas: CKiD-Cr, CKiD-CysC, CKiD combined-Cr/CysC, Zappitelli-CysC and Zappitelli combined-Cr/CysC. Results: Forty-seven patients were evaluated, 74.5% in CKD stage 1, with median age of 14.1 years, 59.6% had lipo/myelomeningocele. When compared with CKiD-Cr, CysC-based formulas showed lower eGFR ​​(p<0.05), (CKiD-CysC (p<0.001), Zappitelli-CysC (p<0.001), CKiD -Cr/CysC (p<0.001) and Zappitelli combined-Cr/CysC (p<0.05)). When CKiD-CysC was used, 68% of patients moved to a more advanced CKD stage. In patients without independent gait, with lower muscle mass (55.3%), the median eGFR using CKiD-Cr and CKiD combined-Cr/CysC were higher (p<0.05). No differences were found between the two groups using the others CysC-based formulas. Conclusion: In patients with NB and poor muscle mass, CKiD-Cr formula may overestimate renal function. CysC-based formulas seem more reliable in these patients, especially in those with greater muscular atrophy.