Anorectal Surgeries – Lecture 1
Anatomy of the Rectum
The rectum differs from the colon in several important anatomical features:
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The outer longitudinal muscle layer is continuous (formed by the fusion of the three taeniae coli).
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Total length: approximately 12–15 cm.
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It lacks:
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Mesentery (in most of its length)
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Sacculations (haustra)
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Appendices epiploicae
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Curvatures of the Rectum
The rectum has three lateral curvatures:
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Upper curve – convex to the right
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Middle curve – convex to the left
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Lower curve – convex to the right
Valves of Houston (Transverse Rectal Folds)
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These are internal infoldings of the rectal wall corresponding to the lateral curvatures.
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They project into the lumen.
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Important during:
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Rectal biopsy
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Proctosigmoidoscopy
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These folds must be carefully negotiated during endoscopic procedures.Biopsy from these sites carries a very low risk of perforation.
The middle rectal fold is an important landmark:
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It marks the level of anterior and posterior peritoneal reflection.
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Extra caution is required when excising polyps above this level.
Relations of the Rectum
Posterior Relations
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Sacrum
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Coccyx
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Levator ani muscle
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Coccygeus muscle
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Median sacral vessels
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Roots of the sacral nerve plexus
Anterior Relations
In Males
Extraperitoneal relations:
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Prostate
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Seminal vesicles
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Vas deferens
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Ureters
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Urinary bladder
Intraperitoneal relations:
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Small intestine
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Sigmoid colon
In Females
Extraperitoneal relations:
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Posterior wall of the vagina
Intraperitoneal relations:
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Upper part of the vagina
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Uterus
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Fallopian tubes
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Ovaries
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Small intestine
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Sigmoid colon
Lateral Relations
Above the peritoneal reflection:
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Small intestine
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Adnexa
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Sigmoid colon
Below the peritoneal reflection:
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Pelvic wall
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Uterus
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Iliac vessels
Denonvilliers’ Fascia
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A delicate layer of connective tissue.
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Separates the rectum from:
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Seminal vesicles
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Prostate
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Vagina
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It has no macroscopically distinct layers.
Fascia Propria of the Rectum
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The rectum is covered anteriorly by visceral pelvic fascia, also known as the fascia propria.
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This fascia separates the rectum from Denonvilliers’ fascia.