Tests for renal function fall into three general groups depending on: (1) The ability of the kidney to excrete from the circulation abnormal substances, such as dyes or drugs which are introduced into it; (2) analysis of the products of metabolism retained in the blood as a result of faulty eliminative powers of the kidney; (3) abnormalities in the physical and chemical properties of the urine.
The phenolsulphonephthalein test is an excellent example of the first group. Rowntree and Geraghty1 have found that the amount of this dye excreted in the urine after its intramuscular or intravenous injection varies almost in proportion to the degree of injury existing in the kidneys. This test is used so generally by clinical and experimental observers that its value in the study of the renal function can be accepted without further comment.
Of substances studied in the blood of nephritics the
FITZ R. STUDY XXIII. THE RELATION BETWEEN AMYLASE RETENTION AND EXCRETION AND NON-PROTEIN NITROGEN RETENTION IN EXPERIMENTAL URANIUM NEPHRITIS. Arch Intern Med (Chic). 1915;XV(4):524-542. doi:10.1001/archinte.1915.00070220026004