Serum creatinine is a poor marker of glomerular filtration rate in patients with spina bifida.

Serum creatinine is used to estimate the glomerular filtration rate (GFR). The serum creatinine, however, may not accurately reflect the GFR in spina bifida patients, who often have decreased overall muscle mass resulting from spinal cord abnormalities. The relationship between the serum creatinine and GFR (obtained by [(125)I]iothalamate clearance) was examined in a population of spina bifida patients. Age-matched patients without spina bifida were used as controls. Results demonstrate that, for serum creatinines above 0.5 mg/dL, serum creatinine is a very poor predictor of GFR. Two patients with serum creatinines of 2.2 mg/dL are near end-stage renal disease with GFRs of 12.5 and 13 mL/minute per 1.73m2 and two patients were initiated on dialysis at the conclusion of the study. It is concluded that obtaining a GFR from a clearance study and not serum creatinine is the only reliable method to assess renal function in spina bifida patients once the serum creatinine is greater than 0.5 mg/dL.