[Principles in the X-ray diagnosis of early stages of renal failure]

The study was undertaken to impart better functional capacities to a urographic study and to convert its results to quantitative characteristics in order to realize its new capacities, namely, to detect early and latent renal functions. Three hundred and fifty-eight patients (165 males and 193 females) aged 3 to 74 years underwent excretory urography using the contrast agent Urografin. In 173 patients, X-ray planimetry determined the index of the renal parenchymatous area and estimated its size in relation to the individual normal value, i.e. the area of the body of the first lumbar vertebra. During urographic studies, 185 patients had a X-ray functional test that was used to determine the glomerular filtration by X-ray contrast agent clearance. A high correlation was established between the area of the parenchyma of the unaffected kidney and the X-ray planimetric area of the body of the first lumbar vertebra (a ratio of 3:1), which offered possibilities of estimating the normal value of parenchymatous tissue for each specific person. A procedure was developed to determine the individual normal glomerular filtration rate by contrast agent clearance. There was evidence for the fact that there was a close relationship of the anatomic parameters of the normal kidneys to their functional ones, which suggests that the filtrability of the glomerular apparatus corresponds to the mass of the intact parenchyma. This has allowed the authors to discover a basic principle of the X-ray diagnosis of renal failure, which consists in recording the parenchymatous tissue size-filtrability imbalance occurring in this condition; this fact may suggest the death of acting nephrons or a temporary reduction in their physiological potential.