The use of lithium clearance measurements as an estimate of glomerulo- tubular function

Abstract

Lithium clearance measurements are based on the observation that lithium undergoes isosmotic reabsorption in the proximal renal tubule to the same extent as salt and water, but undergoes neither reabsorption nor secretion elsewhere in the nephron. Consequently, lithium clearance values estimate the delivery of isosmotic fluid to the loop of Henle and hence provide an assessment of proximal tubular reabsorption of isosmotic fluid. If sodium clearance and urinary flow rate are also measured, then this allows the derivation of a number of parameters relating to both the absolute and relative renal handling of isosmotic fluid in the proximal and distal regions of the kidney. Consequently, lithium clearance techniques can be used in both experimental and clinical studies to evaluate glomerulo-tubular function and provide information regarding the handling of sodium and water by the proximal and distal nephron in both health and disease. The use of lithium clearance measurements in the assessment of glomerulo-tubular function in patients treated with rIL2 for colorectal cancer is described and its application to both drug-induced toxicity and other disease states discussed.