the anatomy of rectum

Presentation by

K Hari Krishnan

I Year MBBS (2008-’09)Tirunelveli Medical College

Tirunelveli, Tamilnadu, India

• Distal part of the large gut

• The pelvic part of the alimentary tract

Rectum

• Posterior part of the lesser pelvis

• In front of lower three pieces of sacrum and the coccyx

• Begins at the rectosigmoid junction– at level of third

sacral vertebra

• Ends at the anorectal junction– 2-3 cm in front of

and a little below the coccyx

• Length– 13 cm (5 in.)

• Diameter– 4 cm (in the upper part)– Dilated (in the lower part)

• Downwards and backwards• Downwards• Downwards and forwards

• Antero-posterior flexures (2 in number)– Sacral flexure

• Follows the curve of the sacrum and coccyx

• Antero-posterior flexures–Perineal flexure / Anorectal flexure

• 80° anorectal angle• In the terminal part of the rectum• At the anorectal junction• Here the rectum perforates the pelvic

diaphragm to become the anal canal

• Lateral flexures (3 in number) – correspond to the transverse rectal folds

• Superior– Convex to the right

• Intermediate– Convex to the left– Most prominent

• Inferior– Convex to the right

• Superior 1/3rd of the rectum– Covered by peritoneum on the anterior

and lateral surfaces• Middle 1/3rd of the rectum

– Covered by peritoneum on the anterior surface

• Inferior 1/3rd of the rectum– Subperitoneal – Devoid of peritoneum

• In males– Upper 2/3rd

• Rectovesical pouch• Coils of ileum• Sigmoid colon

– Lower 1/3rd• Fundus (base) of the urinary bladder• Terminal parts of the ureters• Seminal vesicles• Ductus deferentes• Prostate

• In females– Upper 2/3rd

• Rectouterine pouch, which separates the rectum from the uterus and from the upper part of vagina

• Coils of ileum• Sigmoid colon

– Lower 1/3rd• Lower part of vagina

• Bones– Lower three pieces of sacrum– Coccyx

• Ligaments– Anococcygeal ligament

• Muscles– Piriformis– Coccygeus– Levator ani

• Vessels– Median sacral– Superior rectal– Lower lateral sacral

• Nerves– Sympathetic chain with ganglion impar– Ventral primary rami of S3, S4, S5, Co1– Pelvic splanchnic nerves

• Lymph nodes and lymphatics• Fat

• Superior rectal artery– Direct continuation of Inferior mesenteric artery– Enters the pelvis by descending in the root of the sigmoid

mesocolon and divides into right and left branches, which pierce the muscular coat and supply the mucous membrane

– They anastomose with one another and with the middle and inferior rectal arteries

• Middle rectal artery– Small branch of anterior division of Internal iliac artery– Run in the lateral ligaments of the rectum– Supplies the muscular coat of the lower part of rectum

• Inferior rectal artery– Branch of Internal pudental artery in the perineum– Anastomoses with the middle rectal artery at the anorectal

junction• Median sacral artery

– Direct branch from the dorsal surface of Aorta near its inferior end

– Descends in the median plane– Supplies the posterior wall of the anorectal junction

• Submucosal rectal venous plexus– Surrounds rectum– Communicates

• vesical venous plexus – males• uterovaginal venous plexus – females

– 2 Parts:• Internal rectal venous plexus

– Deep to the epithelium of rectum– Drains into Superior rectal vein

• External rectal venous plexus– External to the muscular wall of rectum– Superior portion: drains into Superior rectal vein– Middle portion: drains into Middle rectal vein– Inferior portion: drains into Inferior rectal vein

• Superior rectal vein– Formed from Internal rectal venous plexus– Consists of 6 main tributary veins– Continues upwards as Inferior mesenteric vein

• Middle rectal vein– Formed from the middle portion of External rectal

venous plexus– Pass alongside middle rectal artery– Drains into the anterior division of Internal iliac vein on

the lateral wall of the pelvis

• Inferior rectal vein– Formed from the inferior portion of the Inferior rectal

vein– Drains into the Internal pudental vein

• Superior half of the rectum– Pararectal lymph nodes, located

directly on the muscle layer of the rectum

– Inferior mesenteric lymph nodes, via either the sacral lymph nodes or the nodes along the superior rectal vessels

• Inferior half of the rectum– Sacral group of lymph nodes or

Internal iliac lymph nodes

• Sympathetic nerve supply– L1, L2 fibres– Through Superior rectal and Inferior

hypogastric plexuses– Vasoconstrictor– Inhibitory to musculature of rectum– Motor to internal sphincter– Carry sensations of pain

• Parasympathetic nerve supply– S2, S3, S4 fibres– Passes via pelvic splanchnic nerves and

inferior hypogastric plexuses to rectal (pelvic) plexus

– Motor to musculature of the rectum– Inhibitory to internal sphincter– Carry sensations of pain and distension

Longitudinal folds

• Present in lower part of the empty rectum

• Effaced during distension

Transverse folds (Houston’s valves or plicae transversae recti)

• Marked in rectal distension

• Superior fold– At beginning of rectum– Projects from the right or the left wall

• Middle fold– Above the rectal ampulla– Projects from the anterior and right

walls– Largest and most constant

• Inferior fold– About 2.5 cm below the middle fold– Projects from the left wall– Variable

• Occasional fourth fold– About 2.5 cm above the middle fold– Projects from the left wall

• Pelvic Floor– Levator ani muscles

• Fascia of Waldeyer– Condensation of pelvic fascia behind rectum– Lower part of ampulla to Sacrum– Encloses Superior rectal vessels and

lymphatics

• Lateral ligaments of Rectum

• Denonvilliers fascia

• Pelvic peritoneum

• Perineal body

• Examination to check for abnormalities of organs or other structures in the pelvis and lower abdomen

• To check for– growths in or enlargement

of the prostate gland in males. A tumor in the prostate can often be felt as a hard lump

– problems in female reproductive organs (uterus and ovaries)

– rectal bleeding or tumors in the rectum

• Proctoscopy - Visual examination of the rectum and anus

• Visualizing the interior of the rectum and anal canal

• Helps in revealing ulcers, abnormal growths and diverticula

• Sigmoidoscope–An endoscope

for viewing the lumen of the sigmoid colon

• Rectocoele• Protrusion of the mucous membrane and submucosa of

the rectum outside the anus for approximately 1–4 cm

• Common in– Children: 1 – 3 years– Elderly people– Middle-aged women

• Rectal mucous membrane and submucous coat protrude for a short distance outside the anus

• Common in children

• Procidentia

• Whole thickness of the rectal wall protrudes through the anus

• A sliding hernia through the pelvic diaphragm

• Common in adults

• Associated with rectal incontinence

Causes

• In infants– Undeveloped sacral curve– Reduced resting anal tone

– diminished support to the mucosal lining of anal canal

• In children– Diminution of fat in

ischiorectal fossae• Diarrhoea• Severe whooping cough• Sudden loss of weight

– Fibrocystic disease– Neurological causes– Mal-development of pelvis

Causes

• In adults– Haemorrhoids– Torn perineum– Straining from urethral obstruction– Following operation for fistula in ano

• In the elderly– Atony of sphincter mechanism

Treatment

• Submucous injections

• Excision of the prolapsed mucosa

• Surgery

• Found mainly in– Rectosigmoid junction– Ampulla

• Bleeding per rectum

• Initial finding – Lymphatics around the bowel

• Later – lymph nodes along superior rectal and middle rectal arteries

• Venous spread – Superior rectal vein to portal vein– Liver – secondary deposits

Treatment

• Rectal excision and total mesorectal excision

• Abdomino-perineal excision with a permanent colostomy

• Adjuvant preoperative radiotherapy

• Liver resection for liver metastases

• Gray’s Anatomy: The Anatomical Basis of Clinical Medicine

• Gray’s Anatomy for Students• Richard S. Snell – Clinical Anatomy by

Regions• Keith L. Moore – Essential Clinical Anatomy• Last’s Anatomy - Regional and Applied• Frank H. Netter – Atlas of Human Anatomy• Bailey and Love’s Short Practice of Surgery