-RECTUM-

RECTUM

FEATURES –

• The rectum is the distal part of the large gut.
• It is placed between the sigmoid colon above and the anal canal below.
• Distension of the rectum causes the desire to defaecate.
• The rectum in man is not straight as the name implies.
• In fact it is curved in an anteroposterior direction and also from side to side.
• The three cardinal features of the large intestine, e.g. sacculations, appendices epiploicae and taeniae, are absent in the rectum.

SITUATION-

• The rectum is situated in the posterior part of the lesser Pelvis, in front of the lower three pieces of the sacrum and the coccyx.

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EXTENT –

• The rectum begins as a continuation of the sigmoid colon at the level of third sacral vertebra.
• The rectosigmoid junction is indicated by the lower end of the sigmoid mesocolon.
• The rectum ends by becoming continuous with the anal canal at the anorectal junction.
• The junction lies 2 to 3 cm in front of and a little below the tip of the

coccyx.

• In males the junction corresponds to the apex of the prostate.

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DIMENSIONS-

• The rectum is 12 cm long.
• In the upper part it has the same diameter of 4 cm as that of the sigmoid colon.
• In the lower part it is dilated to form the rectal ampulla.

COURSE AND DIRECTION –

• Its upper end is continuous with the sigmoid colon and the junction lies in front of the S3 vertebra.
• It passes downward in front of sacrococcygeal curve .
• The lower end of the rectum lies a little below and in front of the tip of the coccyx. This end turns downward and backward and becomes continuous with the anal canal.

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• The beginning and the end of the rectum lie in the median plane, but it shows two types of curvatures in its course.

Two anteroposterior curves:

a. The sacral flexure of the rectum follows the concavity of the sacrum and coccyx.

b. The perineal flexure of the rectum is the backward bend at the anorectal junction.

Three lateral curves:

a. The upper lateral curve of rectum is convex to the right.�b. The middle lateral curve is convex to the left and is most prominent.�c. The lower lateral curve is convex to the right.

Curvatures of the rectum: (a) Anteroposterior

curves, and (b) side to side (lateral Curves)

RELATIONS:-

Peritoneal Relations –

1. The upper one-third of the rectum is covered with peritoneum in front and on the sides.
2. The middle one-third is covered only in front.
3. The lower one-third, which is dilated to form the ampulla, is devoid of peritoneum, and lies below the rectovesical pouch in males and below the rectouterine pouch in females.
4. The distance between the anus and the floor of the pouch is 7.5 cm in males but only 5.5 cm in females.

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FIGURE – Peritoneal Relation of Rectum

Visceral relations-

1.Anteriorly in males :-

• The upper two-thirds of the rectum are related to the rectovesical pouch with coils of intestine and sigmoid colon.
• The lower one-third of the rectum is related to the base of the urinary bladder, the terminal parts of the ureters, the seminal vesicles, the deferent ducts and the prostate.

2.Anteriorly in females :-

• The upper two-thirds of the rectum are related to the rectouterine pouch with coils of intestine and sigmoid colon. The pouch separates the rectum from the uterus, and from the upper part of the vagina.
• The lower one-third of the rectum is related to the lower part of the vagina

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3.Posteriorly:-

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The relations are the same in the male and female. They

are as follows.

1. Lower three pieces of the sacrum, the coccyx and the

anococcygeal ligament.

2. Piriformis, the coccygeus and the levator ani.

3. The median sacral, the superior rectal and the lower

Lateral sacral vessels.

4. The sympathetic chain with the ganglion impar; the

anterior primary rami of S3,S4, S5, coccygeal 1 and

the pelvic splanchnic nerves; lymph nodes,

lymphatics and fat.

Figure:-Posterior relations of the rectum

Mucosal Folds-

• The mucous membrane of an empty rectum shows two types of folds, longitudinal and transverse.

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• The longitudinal folds are transitory. They are present in the lower part of an empty rectum, and are obliterated by distension.

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• The transverse or horizontal folds or Houston’s valves or plicae transversales are permanent and most marked when the rectum is distended.

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• a. The first small transverse fold projects from right wall. It is

About 15 cm above anal canal.

• b. The second transverse fold lies near the upper end of the rectum,

about 8 cm from anus and projects from the anterior and right

walls.

• c. The third transverse fold, the largest and most constant, lies at the

upper end of the rectal ampulla, and projects from the anterior and

right walls. It is some above anus.

• d. The fourth transverse fold which is inconstant lies 2.5 cm below the

middle fold, and projects from the left wall

Figure :-superior view of the transverse mucosal folds of

the rectum

Functional parts of rectum:-

• The rectum has two developmental parts. The upper part related to the peritoneum develops from the Hindgut and lies above the third transverse fold of the rectum.

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• The lower part devoid of peritoneum develops from the cloaca and lies below the third transverse fold.

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• Functionally, the sigmoid colon is the faecal reservoir and the whole of the rectum is empty in normal individuals, being sensitive to distension. Passage of faeces into the rectum, therefore, causes the desire to defaecate.

Arterial supply:-

Superior rectal artery-

• This is the chief artery of the rectum. It is the continuation of the inferior mesenteric artery at the pelvic brim, medial to the Left ureter.
• It lies in medial limb of pelvic mesocolon and divides opposite the third sacral vertebra into right and left branches which run on each side of the rectum.
• Each branch breaks up at the middle of the rectum into several small branches which pierce the muscular coats and run in the anal column up to the anal valves where they form looped anastomoses.

Middle rectal arteries-

• These supply only the superficial coats of the lower rectum.
• They arise from the anterior division of the internal iliac artery, run in the lateral ligaments of rectum, and supply the muscle coats of the lower part of the rectum.
• Their anastomoses with the adjacent arteries are poor.

Median sacral artery-

• This is a small branch arising from the back of the aorta near its lower end.
• It descends in the median plane and supplies the posterior wall of the anorectal junction.

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Figure:- Arterial supply of the rectum

Venous Drainage:-

Superior Rectal vein-

• The tributaries of this vein begin in the anal canal, from the internal rectal venous plexus, in the form of about three veins of considerable size.

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• They pass upwards in the rectal submucosa, pierce the muscular coat about 7.5 cm above the anus and unite to form the superior rectal vein which continues upwards as the inferior mesenteric vein to end in the splenic vein.

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Middle rectal vein-

• The tributaries of this vein drain, chiefly, the muscular walls of the rectal ampulla, and open into the internal iliac veins.

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Median sacral vein-

• It joins left common iliac vein.

Figure:- Venous drainage of Rectum

Lymphatic Drainage:-

1. Lymphatics from more than the upper half of the

rectum pass along the superior rectal vessels to the

Inferior mesenteric nodes after passing through the

pararectal and sigmoid nodes .

2. Lymphatics from the lower half of the rectum pass along

the middle rectal vessels to the internal iliac nodes.

3. Lymphatics from the lower part of anal canal drain into

superficial inguinal nodes.

Figure:- Lymphatic drainage of rectum and anal canal

Nerve supply:-

• The rectum is supplied by both sympathetic (L1., L2)

and parasympathetic (52,53, 54) nerves through the

superior rectal or inferior mesenteric and inferior

hypogastric plexuses.

• Sympathetic nerves are vasoconstrictor, inhibitory to

the rectal musculature and motor to the internal

sphincter.

• Parasympathetic nerves are motor to the musculature of the

rectum and inhibitory to the internal sphincter.

• Sensations of distension of the rectum pass through the

parasympathetic nerves, while pain sensations are carried

by both the sympathetic and parasympathetic Nerves.

Figure:- Nerve supply of rectum

Support of rectum:-

• Pelvic floor formed by levator ani muscles.
• Fascia of Waldeyer; It attaches the lower part of the rectal ampulla to the sacrum. It is formed by condensation of the pelvic fascia behind the rectum. It encloses the superior rectal vessels and lymphatics.
• Lateral ligaments of the rectum; They are formed by Condensation of the pelvic fascia on each side of the Rectum. They enclose the middle rectal vessels, and Branches of the pelvic plexuses, and attach the Rectum to the posterolateral walls of the lesser pelvis.

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• Rectovesical fascia of Denonvilliers:It extends from the rectum behind to the seminal vesicles and prostate in front.
• The pelvic peritoneum and the related vascular pedicles also help in keeping the rectum in position.
• Perineal body with its muscles.

Clinical Anatomy :-

Digital per rectum (PR) examination-

* In PR examination the finger enters anal canal before reaching lower end of rectum.

In a normal person the following structures can be palpated by a finger passed per rectum.

° In males :

1. Posterior surface of prostate.

2. Seminal vesicles.

3. Vas deferens.

° ln females :

1. Perineal body.

2. Cervix.

3. Presenting part of the foetus during delivery.

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° In both sexes:

1. Anorectal ring.

2. Coccyx and sacrum .

3. Ischioanal fossae and ischial spines.

° In patients, a PR examination can help in the palpation of following abnormalities.

a. Within the lumen: Faecal impaction and foreign bodies, bleeding piles or haemorrhoids.

b. In the rectal wall: Rectal growths and strictures, and thrombosed piles.

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c. Outside the rectal wall: In males, the enlargements of prostate, seminal vesicles and bulbourethral glands, and stone inmembranous urethra; in females, enlargements of uterus, tubes and ovaries, and abnormalities in the pouch of Douglas; and in both sexes, the distended bladder, lower ureteric stones, and tumours of the bony pelvis.

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During parturition the dilatation of cervix is commonly assessed through the rectal wall to avoid infection by repeated vaginal examinations.

Digital per rectum examination-

Proctoscopy and sigmoidocopy_-

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∆ The proctoscopy is an instrument through which the interior anal canal and rectum can be examined. However, it may not be possible to see the upper part of the rectum with a proctoscope. A sigmoidoscope can be used for this purpose.

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∆ In passing a sigmoidoscope into the rectum the curvatures of the rectum and the presence of transverse folds within it has to be remembered.

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Proctoscopy and sigmoidocopy-

Prolapse of rectum-

1. Partial prolapse :

Protrusion of the mucous membrane or the entire rectum outside the

anal verge. This condition is common in children and elderly patients

Prolapse can be partial or complete. When protrusion is between 1.25

and 3.75 cm, it is partial prolapse and it is mainly a mucosal prolapse.

Any form of strain including whooping cough or excessive straining

or due to habitual constipation can give rise to partial prolapse of

rectum. It can follow an attack of diarrhoea resulting in loss of fat in

the ischiorectal fossae, which support the rectum.

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B. Complete/total prolapse

It is also called procidentia . Factors have been summarised below.�Pelvic floor: Weakness of pelvic floor can be due to birth injuries or collagen maturation.�Large lateral ligaments: These ligaments are condensation of pelvic fascia on each side of the rectum�Deep rectovesical pouch is often found in prolapse rectum.

Inadequate fixation of the rectum in its persacral bed.

Prolapse of rectum-

Neurological disturbances of the rectum-

In spite of the identical innervation of the rectum and bladder, the rectal involvement in nervous lesions is less severe than that of the bladder.

After sacral denervation of the rectum the peripheral nervous plexus controls the automatic evacuation of the rectum. This reflex activity is more massive and complete when sacral innervation is intact, e.g. complete cord lesion above the sacral region. However, due to weak musculature of the rectum and sparing of the tone of the external sphincter by transverse lesions of the cord, rectal disturbances tend to cause constipation, although complete lesions may cause Reflex defaecation.

Neurological disturbances of the rectum-

Carcinoma of rectum-

Typically, patients are middle-aged around 40-50 years who present with bleeding per rectum or passage of blood and mucus per rectum. Early morning spurious diarrhoea indicates growth in the ampulla of the rectum. Increasing constipation indicates growth in the rectosigmoid junction. Backache indicates sacral infiltration. Per rectal examination can detect almost all cases of carcinoma rectum. Typically, it is hard, indurated and friable-bleeds on touch. Infiltration to the structures around should be carefully looked into. Proctoscopy is an outpatient procedure to take a biopsy and diagnosis. If difficulty arises, sigmoidoscopy or even colonoscopy can be done. Ultrasound is done to rule out liver and lymph nodal metastasis. MRI is the best investigation to see for local infiltration such as bladder base, sacrum, posterior vaginal wall and side wall of the pelvis. When sphincter can be saved, surgery of choice is low anterior resection or high anterior resection. When sphincter cannot be saved, abdominoperineal resection (APR) with a permanent colostomy is the only operation to achieve cure. Adjuvant radiotherapy and chemotherapy are also given. Prognosis is very good for early lesions.

Carcinoma of rectum-

Rectal continence-

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* Rectal continence depends solely on the anorectal ring. Damage to

the ring results in rectal incontinence.

*The surgeon has to carefully protect the anorectal ring in operating

on the Region.

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Rectal continence-

Research paper on rectum

Functional disorders of Anus and rectum

Abstract:-

In this report the functional anorectal disorders, the etiology of which is currently unknown or related to the abnormal functioning of normally innervated and structurally intact muscles, are discussed. These disorders include functional fecal incontinence, functional anorectal pain, including levator ani syndrome and proctalgia fugax, and pelvic floor dyssynergia. The epidemiology of each disorder is defined and discussed, their pathophysiology is summarized and diagnostic approaches and treatment are suggested. Some suggestions for the direction of future research on these disorders are also given.

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Citation:-

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Whitehead, W. E., Wald, A., Diamant, N. E., Enck, P., Pemberton, J. H., & Rao, S. S. C. (1999). Functional disorders of the anus and rectum. Gut, 45(suppl 2), 1155-1159.