The phenolsulphonephthalein test is one of the best known and most reliable of the many procedures which aid in the estimation of the functional activity of the kidneys. Since its introduction by Rountree and Geraghty, it has been employed extensively and has proved to be an invaluable clinical aid. Our knowledge of the significance of the test is purely empirical, however, being based on the evidence presented by thousands of tests, the findings of which have been carefully compared with clinical, experimental and pathological examinations. Hence, any additional data which throws light on the manner of the excretion of phenolsulphonephthalein is always of interest and value.
The following studies seem to indicate that as the ability of the kidney to excrete phenolsulphonephthalein becomes impaired in many cases of chronic interstitial nephritis, the process of excretion becomes more and more one of simple filtration, and the amount of dye eliminated varies