Kidney Stones Diseases

EFFERENT ARTERIOLES -  The efferent arterioles of the juxtamedullary glomeruli are long and have a relatively thick wall. They have not been studied systematically in the human kidney and the following account is based upon their structure in the rat as described by Moffat (1967) and later by other workers (see Moffat 1975 for references). The wall of the juxtamedullary efferent is thicker than that of the cortical efferent since it has a well-developed muscular media. The endothelium is relatively thick and non-fenestrated and it is surrounded by two or three layers of smooth muscle cells. Outside the media there are bundles of non-myelinated nerve fibres, a few fibroblasts and bundles of collagen fibres which separate the arterioles from the surrounding renal tubules. The sphincter-like arrangement of smooth muscle around these arterioles could control the medullary blood flow and in injected animal preparations there often appears to be a narrow constriction at this site (

The medullary capillaries - As the efferent arteriole passes through the subcortical region it gives small branches to the coarse meshed capillary plexus which is found in this region (Fig. 1.9). This plexus is continuous both with the cortical capillary plexus and with a much more dense capillary plexus which occupies the outer medulla. The outer medullary plexus is less conspicuous in the human kidney than in most animals, where it has a closely packed ‘frizzled’ appearance (Fourman & Moffat 1971). The vascular bundles traverse. this plexus (Fig. 1.10) and individual descending vasa recta supply it by peeling off the periphery of the bundles and breaking up into capillaries. These vessels often loop sharply backwards before forming their capillaries, so that in sections where the termination of the vessel may not be visible the appearance may suggest that the vessel is forming a hairpin loop before climbing out of the medulla again. The question of the so-called ‘U-loops wil

Juxtamedullary efferent arterioles -  The efferent arterioles of the juxtamedullary glomeruli differ in many respects from those of the cortical glomeruli, being longer, wider, and having a thicker wall containing a well-developed smooth muscle coat. It should, perhaps, be mentioned here that this terminology for glomeruli (cortical and juxtamedullary) is inaccurate since all glomeruli are in the cortex (or subcortex) but it has been used by so many authors that it has now become a convention. The juxtamedullary glomeruli are those whose efferent arterioles supply the medulla rather than the cortex. Even these, however, are not necessarily juxtamedullary in the geographical sense since some of them lie almost as far out as the middle zone of the cortex. It seems likely that when more is known about changes in the distribution of blood flow through the different layers of the cortex as a result of changes in salt and water balance and in response to various pathological condit

Preglomerular vessels INTERLOBULAR ARTERIES The most obvious vessels of supply to the cortex are the interlobular arteries. These are mostly relatively short, straight vessels which take origin from the convex surface of the arcuate arteries or are formed from the terminations of the latter as they turn up towards the surface of the kidney. They may have an uncomplicated course or they may branch once or twice to give arteries of the second or third order. In the final part of their course they run directly towards the surface except in the renal columns where their arrangement is somewhat complicated. The renal columns of Bertin consist of the fused cortices of adjacent lobes so that there is a cortico-medullary junctional zone on each side of the column. Fig. 1.4: Diagram to show long and short-looped nephrones and their relation to the zones of the kidney. From Moffat (1975), by permission of Cambridge University Press. Arcuate arteries lie in each of these zone

Interlobar and arcuate arteries -  Each segmental artery breaks up into a number of interlobar arteries which run in close relation to the calyceal walls and enter the renal substance proper in the vicinity of the renal columns of Bertin. At this point, or sometimes before, they break up to form arcuate arteries (Fig. 1.2). Both interlobar and arcuate arteries give branches which ramify in the fat and connective tissue around the pelvis and calyces to form an important plexus which will be described later. The arcuate vessels branch out from the interlobar arteries, their arched form being due to the fact that they run in a plane that corresponds approximately to the cortico-medullary junction (Figs 1.2, 1.3 and 1.4/Read: Cortical vessels ). They are not, however, an accurate guide to this junction since a number of glomeruli lie on the medullary side of them, the corresponding afferent arterioles arising directly from the arcuate arteries themselves. The branching out of th

The renal arteries and their branches  -  As befits the very large volume of blood flowing through them, the main renal vessels are short, wide and pass straight from the aorta to the kidney and from the kidney to the inferior vena cava. As the renal artery is traced towards the kidney it gives off one or more branches to the suprarenal (which may come from the apical segmental artery) and other branches to the capsule, the perinephric tissues and the upper part of the ureter. The capsular branches are particularly important-they usually leave the renal artery within the hilum and emerge to supply the capsule on both surfaces of the kidney. They anastomose with a superior capsular artery (usually from the suprarenal branch of the renal artery) and an inferior capsular artery (commonly from the testicular or ovarian artery). The whole network of capsular arteries anastomoses not only with a number of retroperitoneal vessels, particularly the lumbar arteries, but also with the