Monitoring of renal function in patients with spinal cord injury.

OBJECTIVE: To assess the sensitivity of serum creatinine level in detecting clinically important and early deterioration of renal function in patients with spinal cord injury (SCI), and to evaluate the optimal method of determining creatinine clearance in these patients. PATIENTS AND METHODS: The serum creatinine level of 36 patients (25 paraplegics and 11 quadriplegics) was evaluated and compared with the corresponding measured creatinine clearance rate. Correlations were also assessed between the creatinine clearance measured by 24-h endogenous clearance, single-shot 99mTc-labelled diethylenetriamine pentaacetic acid (99mTc-DTPA) clearance technique, and the Cockcroft-Gault formula, to test their validity.
RESULTS: Of the 36 patients 11 (31%) had a measured creatinine clearance of < 100 mL/min (mean 84.8) and a corresponding normal serum creatinine level. Creatinine clearance calculated by the Cockcroft-Gault formula did not correlate well with that measured by the 24-h endogenous clearance (r = 0.426) and 99mTc-DTPA clearance (r = 0. 366), overestimating creatinine clearance in all but three patients. The mean (SD) difference between the creatinine clearance measured by the 24-h and DTPA clearance technique was 17.7 (16.5)% and the correlation between these techniques was good (r = 0.71).
CONCLUSION: Serum creatinine level is not sensitive in detecting early deterioration of renal function in patients with SCI. The Cockcroft-Gault formula generally significantly overestimates the true creatinine clearance and is not recommended. The 24-h endogenous creatinine clearance measured on appropriately collected urine samples is an acceptable accurate and practical method of determining glomerular filtration rate in patients with SCI.