DUODENAL HEENIA. 371 



opening of the diaphragm may be so displaced downwards that 

 it actually encircles part of the stomach below the oesophagus. 



Duodenal hernia may occur in two forms, the right and the 

 left. Of these the left hernia occupies a peritoneal fossa which 

 lies to the left of the duodeno-jejunal junction. The mouth of 

 the sac contains in its left margin the inferior mesenteric vein 

 and usually the left colic artery. These two vessels form by 

 their intersection the vascular arch of Treitz. The hernial sac 

 burrows in the retroperitoneal tissue in a direction outwards or out- 

 wards and upwards. In extreme instances the whole of the small 

 intestine may lie in the sac. When the opening of the sac is in 

 view only the issuing coil of intestine can be seen ; the entering 

 coil being entirely concealed, appears to gain the interior by 

 perforating the sac wall. As the hernia extends in the retro- 

 peritoneal tissue it passes behind the attachment of the ascend- 

 ing and descending colon to the parietal peritoneum, so that the 

 colon becomes closely applied to the front of the sac. Behind the 

 sac lie the psoas and the kidney with the renal vessels. The com- 

 pression to which the inferior mesenteric vein is exposed at the 

 mouth of the sac may give rise to haemorrhoids and bleeding 

 from the bowel. 



The right duodenal hernia is so called because it lies to the 

 right of the spine. The orifice of the sac lies behind and to the 

 left, on the lumbar vertebrae. The hernia appears to originate 

 in a small fossa in the mesentery of the upper part of the 

 jejunum, lying immediately below the transverse portion of the 

 duodenum. The orifice of the sac lies within the concavity of 

 the curve formed by the superior mesenteric artery as that 

 vessel arches downwards and to the right. The aperture may 

 be dragged downwards to the right iliac fossa by the weight of 

 the intestine, and so confounded with hernial orifices in this 

 region. As the hernia develops it establishes relations with the 

 back of the ascending and transverse colon. 



Hernia into a fossa about the caecum is either ileo-caecal 

 or retro-colic. The ileo-colic fossa is not known to be the site 

 of hernia. The ileo-caecal fossa lies between the mesentery of 



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