Blood Flow to the Kidney and Creatinine Clearance. ∗

Abstract

In a series of experiments carried out at the University Hospital, Minneapolis, by one of us (Medes) in collaboration with Dr. Hilding Berglund, it was demonstrated that creatinine clearance may be elevated in hyperthyroidism. In 20 cases of hyperthyroidism the clearance averages 196 ± 8.6 cc. per minute, as compared with a normal average of 173 ± 2.9 cc. per minute. In the former group the range extended from 111 to 338 cc. per minute, whereas in the latter group the highest value found in 60 tests was 296 cc. per minute. That increased blood flow through the kidneys might be one factor responsible for the increased creatinine clearance seemed probable, and the present investigation, undertaken at the suggestion of Dr. Berglund, is an attempt to evaluate this factor.

The thermo-stromuhr method of Rein 1 for measuring blood flow was used because it permits observations to be made under more nearly normal physiologic conditions. 2 , 3 All observations were made on dogs and limited to one kidney, the other having been removed 3 or more weeks prior to the measurement of blood flow. The unit was applied to the renal artery, employing the usual ether anesthesia and sterile technic. After the recovery of the animal observations were begun. The observations were made at intervals of about 15 minutes, and the average value throughout the period was estimated.

Creatinine clearance was measured by the method of Rehberg. 4 Creatinine (1.5 to 2 gm., depending on the weight of the animal) was administered intravenously one hour before readings were started, and 150 to 250 cc. of water was given by stomach tube. All urine was removed by catheter, the bladder was flushed with several washings of physiologic sodium chloride solution and the washings were added to the urine.

Summary and Conclusions. A series of experiments was undertaken to study the relation between creatinine clearance and blood flow. The thermo-stromuhr method of measuring blood flow was used because it permits such observations without the complicating factor of anesthesia. All observations were made on unilateral nephrectomized dogs. A general parallelism but not a direct proportinality between the blood flow to the kidney and the creatinine clearance was observed.