Surgical physiology of the anal muscles and pelvic floor

Above The dentate line

•cubical epithelium;

•autonomic nerves (insensitive);

•portal venous system;

Below The dentate line

•from squamous epithelium;

•from spinal nerves (very sensitive);

•from systemic venous system.

The crypts of Morgagni (syn. anal crypts) are small pockets between the inferior extremities of the columns of Morgagni. Into several of these crypts, mostly those situated posteriorly, opens one anal gland by a narrow duct.

Arterial supply

The anal canal is supplied by branches fromthe superior, middle and inferior haemorrhoidal arteries.

Venous drainage

The superior haemorrhoidal veins drain via the inferior mesenteric vein into the portal system. The superior haemorrhoidal vein drains the upper half of the anal canal. The middle & inferior haemorrhoidal veins drain the lower half of the anal canal and the subcutaneous perianal plexus of veins: they eventually join the external iliac vein (systemic circulation) on each side.

Lymphatic drainage

Lymph from the upper half of the anal canal flows upwards to drain into the para-aortic nodes. Lymph from the lower half of the anal canal drains on each side first into the superficial and then into the deep inguinal group of lymph glands.

Surgical physiology of the anal muscles and pelvic floor

The function of the anal canal and pelvic floor muscles is not only to contain the contents of the rectum, but also to allow effortless, unimpeded voiding at defecation.

INVESTIGATIONS:

· Proctoscopy (Fig. 61.10)

· Sigmoidoscopy (Chapter 60)

· Physiological studies

o Manometry

o Electrophysiology

· Proctography

· Endoluminal ultrasound

CONGENITAL ABNORMALITIES

Early in embryonic life there is a common chamber the cloaca into which open the hind gut and the allantois. The cloaca becomes separated into the bladder and post-allantoic gut (rectum) by the down growth of a septum. About this rime an epiblastic bud, the proctodaeum, grows in towards the rectum. Normally fusion between these two structures occurs during the third month of intrauterine life.

Imperforate anus: (‘agenesis’ and ‘atresia’ of the rectum and anus.). The condition is divided into two main groups: the high (These are often associated with a fistulous connection between the blind rectal stump and the bladder, or other abnormalities of the pelvic structures) and the low, depending on whether the termination of the bowel is above or below the pelvic floor.

PILONIDAL SINUS: (Latin: pilus = hair, nidus= nest).

The reasons which support the acquired theory of origin of pilonidal sinus can be summarised as follows.

• Interdigital pilonidal sinus is an occupational disease of hairdressers, the hair within the interdigital cleft or clefts being the customers’. Pilonidal sinuses of the axilla and umbilicus have also been reported.

• The age incidence of the appearance of pilonidal sinus (82 per cent occur between the ages of 20 and 29 years).

• Hair follicles have almost never been demonstrated in the walls of the sinus.

• The hairs projecting from the sinus are dead hairs, with their pointed ends directed towards the blind end of the sinus.

• The disease mostly affects men, and hairy men most frequently.

• Recurrence is common, even though adequate excision of the track is carried out.

So common was pilonidal sinus among jeep riders in the 1935—45 war, that it became known as ‘jeep bottom’.

Clinical features: There is a chronic or recurring sinus in the midline about the level of the first piece of the coccyx. Typically, a tuft of hair projects from its mouth.

Treatment:

· Conservative treatment

· In acute exacerbation (abscess): abscess should be opened

· Operation should be performed only when the inflammation has been controlled by the measures indicated already(Excise all of the tracks, as stained by blue dye)

ANAL INCONTINENCE

Aetiology of incontinence: Descent(rectal prolapsed), Destruction(malignant tumours, irradiation), Debility(illness), Deficiency(congenital abnormalities), Damage(childbirth), Denervation(spinal injuries), Dementia(senility).

ANAL FISSURE

An anal fissure (syn. fissure in ano) is an elongated ulcer in the long axis of the lower anal canal.suituated in the midline posteriorly (90 % overall). The next most frequent situation is the midline anteriorly.

Aetiology:During defecation the pressure of a hard faecal mass is mainly on the posterior anal tissues, in which event the overlying epithelium is greatly stretched and, being relatively unsupported by muscle, is placed in a vulnerable position when a fecal mass is being expelled. An anterior anal fissure is much more common in women, particularly in those who have borne children. A more recent suggestion supported by Doppler flow studies is that a fissure is due to ischaemia. It may be that the cause is a combination of trauma initially perpetuated by a poor blood supply.

other causes:

· an incorrectly performed haemorrhoidectomy(in which too much skin is removed).

· inflammatory bowel disease — particularly Crohn’s disease;

· sexually transmitted diseases.

Pathology

An anal fissure is either acute or chronic. Acute anal fissur e is a deep tear through the skin of the anal margin extending into the anal canal. There is little inflammatory induration or oedema of its edges. There is accompanying spasm of the anal sphincter muscle. Chronic anal fissure is characterised by inflamed indurated margins, and a base consisting of either scar tissue or the lower border of the internal sphincter muscle. The ulcer is canoe-shaped, and at the inferior extremity there is a tag of skin, usually oedematous. This tag is known picturesquely as a sentinel pile ‘sentinel’ because it guards the fissure.

CLINICAL FEATURES: Pain on defecation, Bright red bleeding, Mucus discharge,Constipation. On examination a sentinel skin tag can usually be displayed,a tightly closed, puckered anus, the lower end of the fissure can be seen (Because of the intense pain it causes, digital examination of the anal canal should not be attempted at this stage).The diagnosis must be established beyond doubt, for which a general anaesthetic may be required.

Differential diagnosis: Carcinoma of the anus, skin diseases, inflammatory bowel disease, homosexual practices, Tuberculous ulcer, Proctalgia fugax.

TREATMENT:

· Conservative treatment (Glyceryl trinitrate, being a nitric acid donor, when applied as an ointment (0.2 per cent by weight) to the anal canal produces sufficient relaxation of the sphincter to allow the fissure to heal in up to two-thirds of patients.Other measures include laxatives to ensure the motions are soft, but the stools should not be made watery. Celevac tablets give a soft stool of good bulk which is ideal.

· Operative measures. Lateral anal sphincterotomy

HAEMORRHOIDS

Haemorrhoids (Greek: haima blood, rhoos = flowing) syn. piles1 (Latin: pila= a ball) are dilated veins occurring in relation to the anus. Such haemorrhoids may be external or internal, i.e. external or internal to the anal orifice. The external variety is covered by skin, while the internal variety lies beneath the anal mucous membrane. When the two varieties are associated, they are known as interoexternal haemorrhoids.

The veins which form internal haemorrhoids become engorged as the anal lining descends and is gripped by the anal sphincters. The mucosal lining is gathered prominently in three places (the ‘ anal cushions’), which can be in the areas of the three terminal branches of the superior haemorrhoidal artery. The anal cushions are present in embryonic life and are necessary for full continence. Straining causes these cushions to slide downwards and internal haemorrhoids develop in the prolapsing tissues.

Haemorrhoids may be symptomatic of some other condition

· in carcinoma of rectum. This, by compressing or causing thrombosis of the superior rectal vein, gives rise to haemorrhoids.

· during pregnancy. Pregnancy piles are due to compression of the supe­rior rectal veins by the pregnant uterus and the relaxing effect of progesterone on the smooth muscle in the walls of the veins, plus an increased pelvic circulating volume;

· from at raining at micturition consequent upon a stricture of the urethra or an enlarged prostate;

· from chronic constipation.

CLINICAL FEATURES: Bright red painless bleeding, Mucus discharge, Prolapse

First-Degree Haemorrhoids:Haemorrhoids that bleed but do not prolapse outside the anus, or the protrusion is slight and occurs only at stool, and reduction is spontaneous.

2cond-Degree Haemorrhoids Haemorrhoids that prolapse on defecation but return or need to be replaced manually and then stay reduced.

3rd-Degree Haemorrhoids Haemorrhoids that are permanently prolapsed

Investigation: By inspection,Digital examination,proctoscope, Sigmoidoscopy should be done as a precaution in every case

Complications:

· Profuse haemorrhage is not rare.

· Strangulation.

· Thrombosis.

· Ulceration.

· Gangrene

· Fibrosis.

· Suppuration

· Pylephlebitis (syn. portal pyaemia). Theoretically, infected haemorrhoids should be a potent cause of portal pyaemia and liver abscesses,Although cases do occur from time to time, this complication is surprisingly infrequent.

Treatment of haemorrhoids

· Symptomatic

· Injection of sclerosant

· Banding

· Photocoagulation(infrared coagulation).

· Cryosurgery(The extreme cold -196C⁰, liquid nitrogen)

· Haemorrhoidectomy(third-degree haemorrhoids; failure of nonoperative treatments of second-degree haemorrhoids; intero-external haemorrhoids when the external haemorrhoid is well defined).

Haemorrhoidectomy: can be performed using an open or a closed technique(the wound is sutured).

Complications of haemorrhoidectomy

· Early: (Pain, Reactionary haemorrhage, Acute retention of urine).

· Late:Secondary haemorrhage, Anal fissure, Anal stricture

ANORECTAL ABSCESSES:In 60 percent of cases the pus from the abscess yields a pure culture of Escherichia coli; in 23 per cent a pure culture of Staphylococcus aureus is obtained. In diminishing frequency, pure cultures of Bacteroides,a Streptococcus or Proteus strain are found. In many cases the infection is mixed. In a high per­centage of cases — some estimate it as high as 90 per cent —the abscess commences as an infection of an anal gland.

A large percentage of anorectal abscesses coincides with a fistula in ano.

Differential diagnosis: an abscess connected with a pilonidal sinus, Bartholin’s gland.

Classification

Perianal(60 %), ischiorectal(30 %), submucous(5 %) and pelvirectal(a pelvic abscess and, as such, is usually secondary to appendicitis, salpingitis, diverticulitis or parametritis).

Treatment. Operation should be undertaken early Operation. Stage 1.A cruciate incision,& deroofing.

Stage 2. the treatment should be as for fistula.

FISTULA IN ANO

A fistula in ano is a track, lined by granulation tissue, which connects deeply in the anal canal or rectum and superficially on the skin around the anus. It usually results from an anorectal abscess which burst spontaneously or was opened inadequately.The fistula continues to discharge and, because of constant reinfection from the anal canal or rectum, seldom, if ever, closes permanently without surgical aid.

Types of anal fistulae

These are divided into two groups, according to whether their internal opening is below or above the anorectal ring.

· Low-level fistulae open into the anal canal below theanorectal ring.

· High-level fistulae open into the anal canal at or above theanorectal ring.

THE PARKS’ CLASSIFICATION, both a high trans sphinctenic and a supralevator fistula would qualify as high, with the intersphincteric falling into either category depending on whether an internal opening was present at all, and at what level it entered the anal canal

GOODSALL’S RULE. Fistulae with an external opening in relation to the anterior half of the anus tend to be of the direct type (Fig. 61.41). Those with an external opening or openings in relation to the posterior half of the anus, which are much more common, usually have curving tracks, and may be of the horseshoe variety. Note that posteriorly situated fistulae may have multiple external openings which always connect to a solitary internal orifice, usually midline.

Examination:

· Digital examination Not infrequently an internal opening can be felt as a nodule on the wall of the anal canal.

· Proctoscopy sometimes will reveal the internal opening of the fistula

· The injection of lipiodol, or other opaque medium, along the sinus(radiology).

· Endoluminal ultrasonography

· magnetic resonance imaging are being developed as techniques for ‘mapping’ complex fistulae.

TREATMENT.

· fistulotomy.

· fistulectomy.

· A seton (i.e. a ligature of silk, nylon, silastic or linen) is helpful when the internal opening is near the anorectal ring. Insertion of a seton and subsequent reexamination of the patient without anaesthesia will establish whether the internal opening is situated so near to the anorectal ring that incontinence would result if the track were laid open.

· A traumatic fistula usually needs a colostomy.

Malignant tumours

· Squamous cell carcinoma(Radiation, Anal warts sometimes take on a carcinomatous change e.g: in HIVpositive individuals, a long-standing fistula in ano.

· Basaloid carcinoma(nonkeratinising squamous carcinoma)

· Mucoepidermal carcinoma

· Basal cell carcinoma

· Malignant melanoma

· Anal intraepithelial neoplasia (AIN)

· Lymphoma

The traditional treatment for carcinoma of the anal canal

· abdominopenineal excision, removing the growth and perianal area widely.

conservative approach(Radiotherapy alone" by external beam, interstitial and intracavitary", chemo radiation

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