Use of a three-blood-sample plasma clearance technique to measure GFR in horses

Measurement of renal function in horses poses a particular challenge becaus e plasma creatinine is influenced by muscle mass which is highly developed and variable between individuals, while conventional clearance methods invo lve potentially daunting problems, particularly urine collection and bladde r washout. This paper provides data which enable technetium-diethyleneamino pentacetic acid (Tc-DTPA) clearance to be used to calculate glomerular filt ration rate (GFR)/extracellular fluid volume (ECFV) as an expression of GFR in horses, as previously validated in humans, dogs and calves. Apart from being arguably a more physiological expression of GFR than using derivative s of body weight, the use of GFR/ECFV eliminates a source of delay and erro r, namely measurement of the injected dose, and offers the convenience of r equiring only three blood samples. It therefore has advantages for both res earch and clinical applications. (C) 1999 Harcourt Publishers Ltd.