THE PERITONEUM 



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admits the little finger into the fossa to the depth of from four-fifths to one and one- 

 fifth inches, or 2 to 3 cm. The fossa is bounded above by the pancreas, to the right 

 by the aorta, and to the left by the kidney; beneath is the left renal vein. The 

 fossa exists in from 15 to 20 per cent, of cases, and has never yet been found 

 in conjunction with any other form of duodenal fossa, (d) Paraduodenal fossa or 

 the fossa of Landzert (recessus duodenojejunalis) is most distinct in the infant, 

 and is to the left of the ascending portion of the duodenum. The fold of peri- 

 toneum to its outer side and above is produced by the inferior mesenteric vein. 

 Its lower limit is a fold called the mesentericomesocolic fold. (e) The retro- 

 duodenal fossa (Fig. 980) was described in 1893 by Jonnesco. It is a peritoneal 

 cul-de-sac, sometimes found behind the horizontal and ascending portions of the 

 duodenum. 



2. Pericecal Folds and Fossae. There are at least three pouches or recesses to be 

 found in the neighborhood of the cecum, which are termed pericecal fossae. (1) 

 The ileocolic fossa or superior ileocecal (recessus ileocecalis superior) (Fig. 991) 



Epiploic appendages. 



Ileocolic fold. 



Superior ileocecal 

 recess. 



Cecaljold 



Retrocecal recess. I/eocecal fold. 



FIG. 991. The pericecal folds and fossae. 



is formed by a fold of peritoneum, the ileocolic fold, arching over the branch of 

 the ileocolic artery which supplies the ileocolic junction. The fossa is a narrow 

 chink situated between the ileocolic fold in front, and the mesentery of the small 

 intestine, the ileum, and a small portion of the cecum behind. (2) The ileocecal 

 or ileoappendicular fossa (recessus ileocecalis inferior) (Fig. 991) is situated behind 

 the angle of junction of the ileum and cecum. It is formed by a fold of peri- 

 toneum, the ileocecal fold (plica ileocecalis), or "bloodless fold" of Treves, the 

 upper border of which is attached to the ileum, opposite its mesenteric attach- 

 ment, while the lower border, passing over the ileocecal junction, joins the 

 mesentery of the appendix, and sometimes the appendix itself; hence this fold 

 is sometimes called the ileoappendicular fold. Between this fold and the mesen- 

 tery of the vermiform appendix is the ileocecal fossa. It is bounded above by 

 the posterior surface of the ileum and the mesentery; in front and below by the 

 ileocecal fold, and behind by the upper part of the mesentery of the appendix. 

 (3) The retrocecal or subcecal fossa (recessus retrocecalis) (Fig. 992) is situated 



