THE ABDOMElsf 753 



the aorta, and cross the crura of the diaphragm on their way to the 

 hila of the kidneys, the right vessel passing behind the inferior 

 vena cava, second part of the duodenum, and head of the 

 pancreas, whilst the left passes behind the body of the pancreas. 

 Each vessel has its own vein in front of it, and the aortico-renal 

 ganglion lies over its root. On approaching the renal hilum each 

 vessel divides into three or four branches, one of which usually 

 passes behind the pelvis of the kidney, whilst the others lie between 

 the renal vein in front and the pelvis behind. For the subsequent 

 distribution of the branches in the kidney, see p. 822. 



Before breaking up into its proper renal branches the vessel gives 

 oS an inferior capsular artery to the suprarenal capsule, peri-renal 

 branches to the capsule, and ureteric to the upper part of the 

 ureter. 



Differences between the Renal Arteries. — (i) The right artery is 

 rather lower than the left. (2) The right is rather longer than the 

 left, on accoimt of the inclination of the aorta to the left of the 

 middle line. (3) The right passes behind the inferior vena cava, 

 second part of the duodenum, and head of the pancreas, whilst the 

 left passes behind the body of the pancreas. 



Varieties. — 1. Very often there is an accessory renal artery present, arising 

 close to the main vessel, and usually above it. 2. The renal artery may 

 divide into its renal branches close to its origin. 3. There may be an aberrant 

 renal artery, which may arise frofti the inferior phrenic, spermatic (or ovarian), 

 inferior mesenteric, common or external iUac, or middle sacral. 4. In cases 

 of variations, or even in the normal condition, one or more of the renal branches 

 may fail to enter the hilum, and may pierce the kidney on its anterior surface, 

 or near the upper or lower end. 



The renal veins, like the arteries, are of large size. Each lies 

 in front of its artery, and receives tributaries from the adipose tunic 

 and the upper part of the ureter. The vessels are tributaries of 

 the inferior vena cava, which they join almost at a right angle, 

 the left a little higher than the right. The left vein crosses in 

 front of the aorta, taking up in its course the left suprarenal and 

 left spermatic (or ovarian) veins. In some cases there is a single 

 semilunar valve at the lower part of the opening of each renal vein 

 into the inferior vena cava. 



Difference between the Renal Veins. — (i) The left vein is longer 

 than the right, on account of the position of the inferior vena cava on 

 the right side. (2) The left is rather higher than the right. (3) The 

 left crosses in front of the aorta. (4) The left receives the left 

 suprarenal and left spermatic (or ovarian) veins. 



The renal veins originally open into the cardinal veins. Subsequently the 

 right renal vein opens into the junction of the upper and lower segments of 

 the inferior vena cava. \\Tien the left cardinal vein becomes obliterated, 

 in great part the left renal vein becomes continuous with the left division 

 of the primitive inferior vena cava. The mesial portion of the left renal 

 vein is developed from the left division of the priaiitive inferior vrua 

 ca'a. 



48 



