Several different techniques are available for estimating renal function in man. Some of these measure very accurately discrete and specific functions, such as glomerular filtration rate, renal blood flow, and maximum rates at which the tubules can transport materials (Tm). These methods, however, are time-consuming, expensive, and unsuitable for routine clinical use. The clinical methods for estimating renal function, such as the blood urea nitrogen content, the urea or creatinine clearance, phenolsulfonphthalein excretion, and urinary concentrating ability, are reasonably accurate and very useful in evaluating bilateral renal disease. However, these tests rarely are of diagnostic value and, in the absence of ureteral catheterization, are of no value in detecting unilateral renal disease.
Recently, Winter, Taplin, and co-Work-ers 1,2 have introduced a new method for studying renal function, the radioactive iodopyracet (Diodrast) renogram, that appears to be of practical clinical value although it is not a precise measure of any specific