[Importance of the renal interstitium for kidney function].

After presentation of the structure of the cortical interstitium, numerous examples are cited illustrating the significance of the cortical interstitium for the function of the glomeruli and the tubular epithelium. Details are presented showing that every form of interstitial fibrosis increases the resistance of the postglomerular capillary network through the obliteration of the postglomerular capillaries and therefore negatively influences the function of the filter organ by hindering the outflow of blood from the glomeruli. It is also shown that, when glomerular involvement is isolated (e.g., glomerulonephritis, amyloidosis), even the most severe forms of glomerular nephropathy do not compromise the excretory function of the kidneys if the tubular epithelium and the intertubular capillaries are intact. On the basis of these findings, it is concluded that uremia does not develop in isolated glomerular nephropathy, but that the tubulo-interstitial system is also involved when the serum creatinine concentration is slightly increased in the various forms of "glomerular disease".