314 ABDOMEN 



the terminal part of the duodenum. The retro-duodenal fossa passes 

 upwards behind the terminal part of the duodenum. 



The fossae in the region of the ileo-csecal junction are the anterior ileo- 

 Cczcal, the posterior ileo-c<zcal, and the retro-c<zcal or retro-colic. The 

 anterior ileo-coecal fossa lies behind a small fold of peritoneum which 

 crosses the front of the ileo-coecal junction. Its mouth is directed down- 

 wards and to the left. The inferior ileo-czecal fossa also opens towards the 

 left. It is bounded to the right by the caecum, in front by the terminal 

 part of the ileum and the adjacent part its mesentery, behind by the 

 mesentery of the vermiform process, and below by the//zV# ileo-ccecalis^ a 

 fold of peritoneum which passes from the lower border of the ileum to the 

 anterior surface of the mesentery of the vermiform process or, sometimes, 

 to the process itself. The retro-ccecal or retro-colic fossa passes upwards 

 behind the upper part of the coecum and the lower part of the ascending 

 colon ; when this fossa is present the vermiform process usually lies in it. 



The inter-sigmoid fossa also should be looked for at this stage, in 

 order that, if it is present, its boundaries may be examined before they are 

 interfered with by dissection. It runs upwards behind the root of the 

 pelvic meso-colon, at the left side of the last lumbar vertebra. To find it, 

 turn the pelvic part of the colon upwards. 



Dissection. After the occasional peritoneal fossae which 

 happen to be present have been examined make an incision 

 through the peritoneum of the right side of the root of the mesen- 

 tery, from its upper to its lower end, and reflect the right layer of 

 the mesentery towards the gut from above downwards. As the 

 reflection proceeds take away the fat which lies between the 

 two layers and clean the structures which are exposed. They 

 are (i) the trunk of the superior mesenteric artery surrounded 

 by the superior mesenteric plexus of nerves, lying along the root 

 of the mesentery ; (2) the superior mesenteric vein, which lies 

 usually to the right of the artery ; (3) the intestinal branches 

 of the superior mesenteric artery, passing to the wall of the gut ; 



(4) the accompanying veins, nerves, and lymph vessels ; and 



(5) the mesenteric lymph glands, which lie in the intervals 

 between the blood-vessels ; they are scattered at varying distances 

 from the border of the gut to the superior mesenteric trunk in 

 the root of the mesentery. 



After the structures which lie between the two layers of 

 the mesentery have been cleaned make an incision through the 

 peritoneum on the posterior wall of the abdomen from the upper 

 end of the root of the mesentery to the upper end of the ascend- 

 ing colon, then reflect the peritoneum, below the level of the 

 incision, downwards and to the right to the medial margin of 

 the ascending colon and the ileo-caecal junction. Now clear 

 away the extra-peritoneal fat which is displayed, and expose 

 the structures which lie on the posterior wall of the abdomen 

 between the root of the mesentery and the ascending colon. 

 Most superficially, immediately behind the peritoneum, will be 

 found the right colic and ileo-coltc branches of the superior 

 mesenteric artery, with the accompanying veins, nerves, lymph 

 vessels and glands. In the upper part of the region, directly 

 below the root of the transverse meso-colon, the lower part 

 of the descending portion and the right part of the inferior portion 

 of the duodenum will be found, with the superior mesenteric 

 artery and vein, crossing in front of the inferior portion. Behind 





