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- Blood supply to superior rectum
- Superior hemorrhoidal artery from inferior mesenteric artery --> drains into superior rectal veins --> inferior mesenteric vein --> portal vein
Blood supply to middle rectum
Middle hemorrhoidal arteries from internal iliac arteries --> drains into middle rectal veins --> internal iliac veins --> systemic circulation
Blood supply to inferior rectum
Inferior hemorrhoidal arteries from the internal pudendal arteries --> inferior rectal veins --> drains into pudendal veins --> systemic circulation
Internal anal sphincter is a continuation of what layer?
- Circular muscular layer of the rectum
- Involuntary sphincter made of smooth muscle
3 layers of the external anal sphincter:
- Deep - in continuity with levator ani muscle
Cancer of upper and middle rectum treated with:
Low anterior resection = removal of distal sigmoid & ~1/2 rectum with primary anastomosis of proximal sigmoid to the distal rectum
Treatment of low rectal cancers:
Abdomioperineal resection = removal of lower sigmoid colon and entire rectum and anus, leaving a permanent proximal sigmoid colostomy
Typical locations for hemorrhoids:
- Left lateral
- Right anterior
- Right posterior
Describe the supralevator space
- Located above the levator ani on both sides and communicates with the contralateral side posteriorly (can form horseshoe abscess)
- Bounded superiorly by the peritoneum, laterally by the pelvic wall, medially by the rectum, and inferiorly by the levator ani.
Describe the retrorectal space
- Lies above the rectosacral fascia between the upper two thirds of the rectum and sacrum. The fascia runs downward and forward from the sacrum to the anorectal junction.
- Bounded anteriorly by the rectum, posteriorly by the presacral fascia, laterally by pelvic side wall, superiorly by the peritoneal reflection, inferiorly by the rectosacral fascia
Contains loose connective tissue and is a site for formation of tumors arising from embryologic remnants (dermoids, teratomas, & chordomas)
Describe the ischiorectal space
Lies below the levator muscle, above the transverse septum of the ischiorectal fossa, and between the external sphincter and lateral pelvic wall
Communicates posteriorly through the deep postanal space --> horseshoe abscess
Describe the deep postanal space
- Lies between the levator ani and the superficial external sphincter.
- Lower border is the anococcygeal ligament
Origin and insertion of the anococcygeal ligament
- Origin = superficial portion of the external sphincter in the midline
- Insertion =
What is a horseshoe abscess?
- Abscess in the deep poatanal space extends to both ischiorectal spaces
- Can form in perianal, ischiorectal, and supralevator spaces
Describe the perianal space
- Lies superficial to the superficial external anal sphincter
- May connect posteriorly to contralateral side forming a horseshoe abscess
- Most common space involved in abscesses
Describe the intersphincteric space
Lies within the conjoined longitudinal muscle where anal glands are located
What are internal hemorrhoids?
Submucosal cushions located above the dentate line.
Type of tissue above the dentate line =
Type of tissue below the dentate line =
What are external hemorrhoids?
Dilated veins of the inferior hemorrhoidal plexus located below the dentate line
Internal hemorrhoid staging:
- Stage 1 - no prolapse
- Stage 2 - prolapse & spontaneously reduce
- Stage 3 - prolapse, require manual reduction
- Stage 4 - prolapsed, cannot be reduced