What are the best ways to estimate kidney clearance in the elderly?
Given loss of muscle mass with age, serum creatinine may not be the most useful marker for estimating kidney clearance. When appropriately collected, 24-hour urine creatinine clearances can be useful to measure steady-state clearances in the elderly. Formulas derived from 24-hour urine collections of populations of elderly with and without kidney disease are frequently used to estimate GFR at the bedside, minimizing frequent cumbersome 24-hour urine clearances in the elderly. Radioisotopes including iothalamate or iohexol X-ray fluorescence can be accurate; however, expense, radioactivity exposure, and availability limit these procedures for routine GFR measurements