THE ABDOMINAL CAVITY 351 



colic flexure are then stripped medially and the whole of the 

 anterior surface of the kidney can be exposed. 



The peritoneum must not be incised along the medial border 

 of the bowel lest the colic vessels be injured. Further, in the 

 excision of either kidney, the possible presence, generally at the 

 lower pole, of one or more supernumerary renal arteries must be 

 remembered. 



The trans-peritoneal operation for excision of the kidney 

 possesses one great advantage over the lumbar or extra-peritoneal 

 operation, namely, that the surgeon is able to palpate both 

 kidneys through the incision in the abdominal wall. 



Structure of the Kidney, The hilum of the kidney leads into a space, 

 termed the renal sinus, into the cavity of which numerous renal papillae 

 project. On section, the kidney is seen to possess a narrow cortical and a 

 deeper medullary layer. The latter is darker in colour and striated in appear- 

 ance, and is subdivided into a number of small pyramids, the apices of which 

 constitute the renal papillae. 



At the hilum the ureter becomes greatly dilated to form the renal pelvis 

 (pelvis of ureter), which divides into two or sometimes three calyces majores. 

 Each calyx major subdivides into smaller calyces, and each of the latter is 

 associated with one or more renal papillae, receiving the urine from the 

 uriniferous tubules which open on their surfaces. 



Calculi may form in the kidney, calyces, or renal pelvis, 

 and give rise to hydronephrotic changes by obstructing the 

 urinary outflow ; on the other hand, a stone may lie latent for 

 a considerable period. 



A stone or stones lying in the renal pelvis may be removed 

 by incising the pelvis and without cutting into the kidney. 

 This is best carried out by the lumbar route, and after the kidney 

 has been brought to the surface, it is turned slightly forwards 

 and the pelvis is incised horizontally. Occasionally one or 

 more of the renal vessels may intervene, but these may be 

 retracted out of the way. The pelvis heals extremely readily, 

 and there is no danger of establishing a fistula. 



The Renal Arteries arise from the aorta a little below the 

 transpyloric plane. The right one passes behind the vena cava 

 inferior, the head of the pancreas, the second part of the 

 duodenum, and its own vein. The left one passes behind the 

 body of the pancreas and the left renal vein. 



In the renal sinus the terminal branches of the renal artery 

 divide into ventral and dorsal groups. Brodel has pointed out 

 that an incision along the convex lateral margin of the kidney 

 cuts through the principal arteries of the ventral group, and he 

 suggests that incisions should be made slightly behind that 



