Rectal arteries middle

Absorption from the rectum depends on various physiological factors such as surface area, blood supply, pH, fluid volume, and possible metabolism by microorganisms in the rectum. The rectum is perfused by the inferior and middle rectal arteries, whereas the superior, the middle, and the inferior rectal veins drain the rectum. The latter two are directly connected to the systemic circulation the superior rectal vein drains into the portal system. Drugs absorbed from the lower rectum are carried directly into the systemic circulation, whereas drugs absorbed from the upper rectum are subjected to hepatic first-pass effect. Therefore, a high-clearance drug should be more bioavailable after rectal than oral administration. The volume of fluid in the rectum, the pH of that fluid, and the presence of stool in the rectal vault may affect drug absorption. Because the fluid volume is... 

Figure 3.6. Formation of a diverticulum, (A) A cross-sectiun of the wail of the colon reveals the mucasal layer (top surface of diagram), pari of the belt of muscle that encircles the gut, and an artery passing through a naturally occurring gap in the muscle. (B) As middle age approaches, weak spots may develop in places where there exist gaps between muscles-(C) Diverticuli develop. The artery follows the path of the outpouching, and it is this part of the artery that may rupture and bleed and produce rectal bleeding in persons with diverticular disease. (Redrawn with permission from Meyers ef ai, 1976.)...

The IMA supplies colon distal to the splenic flexure including the descending colon, sigmoid colon, and rectum. When embolizing rectal branches off of the superior hemorrhoidal branch of the IMA, one must remember the rich collateral network around the rectum with middle hemorrhoidal branches arising from the internal iliac arteries. The internal iliac arteries should be studied after embolizing a rectal branch to exclude the possibility of collateral flow to the bleeding site. 

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