Estimation of glomerular filtration rate in conscious dogs following a bolus of creatinine

The renal clearance of creatinine was measured following orogastric administration in conscious dogs. Values of creatinine clearance were compared with simul taneously determined values of inulin clearance, when urine volume, glomerular filtration rate and volume status were acutely altered by a variety of experimental manoeuvres. At urine volumes greater than 20 μl. min^?1 · kg^?1, creatinine clearance was not significantly different from inulin clearance. At low urine volumes there was some evidence of creatinine reabsorption. It is concluded that the bolus creatinine technique provides reliable estimates of glomerular filtration rate and is particularly applicable to long-term studies in conscious dogs.