Validation of ‘Transit Renography’ for the Determination of the Intrarenal Distribution of Plasma Flow: Comparison with the Microsphere Method in the Anaesthetized Rabbit and Pig

1. The spectrum of transit times of sodium o-iodohippurate (Hippuran) through the kidney can be derived from an 131I- (or 123I-) labelled Hippuran renogram by deconvolution. In the rabbit and pig, as has previously been shown in man, the frequency distribution curve for the transit times was bimodal. Since the transit time is likely to be proportional to the nephron length, the area of the first mode is likely to represent plasma flow to the shorter outer cortical nephrons whereas the delayed mode represents flow to the long juxtamedullary nephrons. 2. This interpretation was tested by simultaneously comparing renography with the microsphere method of measuring intrarenal plasma flow distribution in 12 rabbits and two pigs with a variety of anaesthetics. A close agreement was found between both methods for the percentage of plasma flow distributed to the outer cortical nephrons, thus supporting the use of ‘transit renography’ to determine the intrarenal distribution of plasma flow.

Applications of Computer Produced Frequency Distribution Curves

A method is described for determining the diagnostic significance of test results. It is based upon the relation of a test value to a frequency distribution curve of patients with a particular disease, and to a curve of others without that disease. When the two curves overlap at the test value found, the results are evaluated in terms of the probability of the patient corresponding to either of the two curves. The evaluation of results in terms of probabilities is more descriptive than the classification of all answers as either "normal" or "abnormal" and permits the combination of probabilities obtained from a number of tests into a single, resultant probability. The most probable diagnosis of a given patient, based upon all the tests done, or the most discriminating combination of tests for the diagnosis of any disease can be determined. The method permits compensation for such factors as a patient's age and sex, or the stage of a disease. It is nonparametric, and can be performed automatically with a data-processing system.

Comparison of dye-dilution and flowmeter estimates of pulmonary valve incompetence in dogs

Quantitative estimates of backflow were obtained in dogs with experimental pulmonary valve incompetence by means of a bristle flowmeter and the dye curve variance method. The variance of the curve was found to be the best index of indicator dispersion and is calculated from analogy to a frequency distribution curve. The method postulates that (forward flow + backflow)/forward flow = variance observed during incompetence/Vx(F; V), where Vx(F; V) is the expected variance for the same forward flow and volume between injection and sampling sites and is determined from regression equations calculated from data of normal dogs. There was good agreement between dye and flowmeter results, provided that Vx(F2;V) was estimated for the specific regression equations obtained from individual dogs. Three or four successive dye curves, obtained while the animal was in a steady state, permitted quantitation of backflow with the accuracy of a single determination of forward flow by the direct Fick or dye method. When Vx(F;V) was estimated from regression equations obtained from the pooled data and normal dogs, agreement with the flowmeter estimates was poor. Submitted on October 28, 1959