Selected monographs.

Date:: 1888

Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs. Source: Wellcome Collection.

85/440 (page 69)

falls, as we have said, below the normal; if, when the occlu- sion is complete, compensation takes place by a retrograde movement of the blood from the spot where the renal vein opens into the inferior vena cava, the pressure in the radicles of the renal vein will become equal to that in the vena cava, and therefore as a matter of course always lower than the normal degree. The case is, of course, different when the vein is occluded, for then the pressure must reach an abnormal height, the degree varying with the degree of completeness of the closure. In consequence, however, of the peculiarity involved in the fact that the majority of the branches of the renal artery break up into the glomerular capillaries before passing into the interstitial capillary system, the increase of pressure in the various por- tions of the vascular system must differ in amount (68). It will be most marked and its occurrence earliest in the inter- stitial capillary system ; it will appear later and in a less degree in the glomerular vessels. The production of oedema, here as everywhere else, necessarily follows as the second direct effect of occlusion of the vein with unimpeded arterial supply. And thus it ifi that this form differs from the ischaemic congestion, which per se does not immediately pro- duce oedema, but which, only after a much longer period, and when in consequence of the deficient supply of blood the nutrition of the tissues has become affected, may be the indirect cause of a dropsical swelling. Thirdly, and lastly, as I have already more than once mentioned, the excretoiy portions of the uriniferous tubules, especially in the medullary substance, are compressed by the congested veins and stag- nation of urine is the result. These three sets of consequences blend with each other and their mutual influence is to some extent contrary, so that it is difficult to separate their effects, and to determine separately the share which each has in the disturbances they jointly produce. The stagnation of urine in particular counteracts to a certain extent the increase of pressure, as already explained. If we therefore leave this complication out of the question, we shall have less difficulty in estimating the effects of tying the vein upon the two factors concerned in the production of urine, always of course supposing that