[Sinus-parenchyma border of the human kidney as the site of origin of intracanalicular and extravascular diffusion of fluids].

Injecting fluids into the kidney against the physiological direction of flow leads to a passage of liquid across the border-line between the renal sinus and the parenchyma. This event, caused by a sudden raising of pressure during the injection is called pyelorenal backflow. It can be divided into a number of subtypes, as there are: pyelocanalicular backflow, pyelosinous backflow, pyelovenous backflow, pyelolymphatic backflow. Among all these phenomena only the pyelocanalicular backflow can be interpreted as a genuine backflow in the fullest sense of the word, while the others never can happen before the fornix had been mutilated. In the case of pyelocanalicular backflow, the contents of the renal pelvis regurgitate into the Ducts of Bellini, but the fluid never goes beyond the collecting ducts in the pyramids. Neither a rupture of the tubuli, followed by an interstitial spreading up to under the capsule, nor a direct penetration into the medullary veins are possible, because the pressure necessary for it causes a rupture of the fornix earlier. This rupture happens step by step as an oblique dissection of the calyx from the papilla. The big calices at the poles show an increased tendency to rupture because they are attached along a line which is shaped like an "8" or like a clover leaf, and so do calices the angle of which is acute. Depending on whether a vein is torn simultaneously with the fornix or not, the contents of the pelvis transflow into the vein (pyelovenous backflow) or into the sinus (pyelosinous backflow). In spite of a previous pyelocanalicular backflow the pelvis is not relieved of pressure to such an extent that there could not occur an additional rupture of the fornix, nevertheless. The pyelosinous backflow leads to a sinus-extravasation which can ascend towards the parenchyma and descend towards the hilum. The ascending sinus-extravasation spreads out within the vascular canals of the kidney. These canals, strictly situated between cortex and medulla, enclose a pyramid (Canales peripyramidales) and contain the interlobar and arcuate bloodvessels. The space between the bloodvessels and the wall of a peripyramidal canal (perivascular space) is filled with connective tissue consisting of 3 components: tunica adventitia of the bloodvessels themselves and fibres originating from the inner capsule and the wall of the calyx. The ascending sinus-extravasation proceeds into the perivascular space by pushing off the bloodvessels from the medulla.(ABSTRACT TRUNCATED AT 400 WORDS)