Comparing Cystatin C- and Creatinine-Estimated Glomerular Filtration Rates in Patients With Thoracic Versus Sacral Motor Levels of Spina Bifida.

OBJECTIVE: Patients with myelomeningocele-type spina bifida are at increased risk of developing kidney disease from neurogenic bladder. Differences between creatinine- and cystatin C-estimated glomerular filtration rates were examined in patients with thoracic versus sacral level myelomeningocele given presumed differences in muscle mass. DESIGN: A retrospective chart review (2005-2018) was performed on 57 adults with myelomeningocele [thoracic n = 44 (77%); sacral n = 13 (23%)]. Concurrently obtained creatinine and cystatin C levels were extracted and calculated creatinine- and cystatin C-estimated glomerular filtration rates were compared. RESULTS: Mean creatinine-estimated glomerular filtration rate was significantly higher for thoracic [140.8 ml/min (SD = 23.9)] versus sacral myelomeningocele [112.0 ml/min (SD = 22.6), P = 0.0003]. There was no difference in cystatin C-estimated glomerular filtration rate between sacral [116.6 ml/min (SD = 23.7)] and thoracic myelomeningocele [124.8 ml/min (SD = 17.9)]. The mean difference between creatinine- and cystatin C-estimated glomerular filtration rates in thoracic myelomeningocele [24.2 ml/min (SD = 16.3)] was significantly greater than in sacral myelomeningocele [-12.8 (SD = 15.7), P < 0.0001]. CONCLUSIONS: There was a significantly higher discrepancy between creatinine- and cystatin C-estimated glomerular filtration rates in thoracic versus sacral motor levels of myelomeningocele. These data suggest that creatinine-estimated glomerular filtration rate may overestimate kidney function in patients with thoracic myelomeningocele. Providers who manage patients with thoracic myelomeningocele should consider monitoring cystatin C to evaluate for underlying renal disease.