Validation and impact of a new technique for assessment of glomerular filtration rate in patients with liver disease.

Abstract

Previously we have proposed a technique for the measurement of plasma clearance in patients with ascites. The impact of using the technique was assessed and the results compared with those from a reference technique in 111 patients having glomerular filtration rate measurements as part of their workup for liver transplantation. Results of calculations using the new technique were compared with plasma clearance measurements obtained using a conventional slope-intercept technique and with clearance measurements based on urine collection. Discrepancies between the results of plasma clearance and urinary clearance assessments were investigated by using an uncollimated gamma camera to measure the total retention of the tracer. Conventional slope-intercept calculations overestimated clearance compared with the new technique by more than 20% in 21% of the patients. Significant differences between the results of the two methods were more likely in patients with more severe ascites. Results of urine collection-based measurements of Cr-51 EDTA clearance were frequently significantly lower than measurements using the new technique, whereas measurements of urinary clearance of creatinine were higher. Gamma camera measurements suggest that discrepancies between total and urinary clearance of Cr-51 EDTA are due to incomplete urine collection. The new technique is a practical method for assessment of kidney function and should be used in patients with liver disease who have or may have ascites.