THE A B D O M E N
Barium enema (Fig. 5.20) If the lumen of the appendix is patent, it may fill on bariumenema examination. The lumen is often obliterated in patients past mid-adulthood. To fill the appendix the patient should be supine because its orifice is on the posterior aspect of the caecum. Some elevation of the head is also helpful. CT and MRI The normal appendix can usually be identified arising from the caecum inferior to the insertion of the terminal ileum. Appendiceal abscess Because the appendix is on a mesentery and mobile, pus from an infected appendix may cause abscess formation in
a variety of locations. Pus may travel inferiorly to the pelvic peritoneum to the rectovesical (or rectouterine) pouch. Pus may also travel superiorly in the right paracolic gutter to the intrahepatic spaces (see section on the peritoneum). THE LARGE INTESTINE (Fig. 5.20) (see also Rectum and Anus in the section on the pelvis) The length of the large intestine is very variable, with an average length of 1.5 m. It is wider in diameter than the small intestine, with a maximum diameter of the caecum at 9 cm and the transverse colon at 5.5 cm. As far as the rectum the colon is marked by taeniae coli. These are three flattened bands of longitudinal muscle that represent the longitudinal muscle layer of the colon. The taeniae converge on the appendix proximally and the Fig. 5.20
Barium study of the colon.
1. Rectum 2. Valve of Houston (lateral mucosal fold) 3. Sigmoid colon 4. Descending colon 5. Splenic flexure 6. Transverse colon 7. Hepatic flexure 8. Ascending colon 9. Caecum 10. Caecal pole 11. Base of appendix 12. Tip of appendix
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