Anal fissure
Definition
An anal fissure (syn. fissure in ano) is an
elongated ulcer in the long axis of the lower anal canal.
Location
The site of election for an anal fissure is
the midline posteriorly (90 per cent overall). The next most frequent
situation is the midline anteriorly.
Aetiology
The
cause of anal fissure, and particularly the reason why the midline posteriorly
is so frequently affected, is not completely understood. A probable explanation
is as follows: the posterior wall of the rectum curves forwards from the hollow
of the sacrum to join the anal canal, which then turns sharply backwards. 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
scybalous mass is being expelled. Possibly some cases are due to tearing down of
an anal valve of Ball. An anterior anal fissure is much more common in women,
particularly in those who have borne children. This can be explained by the lack
of support of the anal mucous membrane by a damaged pelvic floor and an
attenuated perineal body. 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.
Some
causes of anal fissure are certain:
•
an incorrectly performed operation for haemorrhoids in which too much
skin is removed. This results in anal stenosis and tearing of the sear when a
hard motion is passed;
•
inflammatory bowel disease — particularly Crohn’s disease;
•
sexually transmitted diseases.
Pathology
An anal fissure is either acute or chronic.
The upper internal end of the fissure stops at the dentate line. Because the
fissure occurs in the stratified sensitive epithelium of the lower half of the
anal canal, pain is the most prominent symptom (see below).
Acute
anal fissure 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. There may be spasm of the
involuntary musculature of the internal sphincter. In long-standing cases, this
muscle becomes organically contracted by infiltration of fibrous tissue.
Infection is common and may be severe, ending in abscess formation. A cutaneous
fistula may follow.
Chronic
fissure in ano may have a specific cause — often a granulomatous infection,
e.g. Crohn’s disease. Biopsy examination is advisable of any tissue removed
at operation for a chronic fissure. Specific fissures of this type are often
less painful than the appearances of the lesion would suggest.
Clinical
features
1
Symptoms
of anal fissure
2
Pain
on defecation
3
Bright
red bleeding
4
Mucus
discharge
5
Constipation
The condition is more common in women and
generally occurs during the meridian of life. It is uncommon in the aged,
because of muscular atony, whereas anal fissure is not rare in children, is
sometimes encountered during infancy and may cause acquired megacolon (Chapter 57).
• Pain is the symptom — sharp,
agonising pain starting during defecation, often overwhelming in intensity and
lasting for
an hour or more. As a rule, it ceases suddenly, and the sufferer is
comfortable until the next action of the bowel. Periods of remission occur for
days or weeks. The patient tends to become constipated
rather than go through the agony of defecation. (One patient accustomed
himself to take a generous dose of senna on Saturday night, and retire to the
toilet on Sunday morning with a bottle of whisky and the newspaper.)
• Bleeding — this is usually slight and consists of bright streaks on the stools
or the paper.
• Discharge. A slight discharge accompanies fully established
cases.
On examination
In cases of some standing, a sentinel skin tag
can usually be displayed. This, together with a typical history and a tightly
closed, puckered anus, is almost pathognomonic of the condition. By gently
parting the margins of the anus, the lower end of the fissure can be seen (Fig.
61.23).
Because
of the intense pain it causes, digital examination of the anal canal should not
be attempted at this stage unless the
fissure cannot be seen, or it seems imperative to exclude major intrarectal
pathology. In these circumstances, the local application of a surface
anaesthetic such as 5 per cent
xylocaine on a pledget of cotton wool, left in place for about 5
minutes, will enable the necessary examination to be made. In early cases,
the edges of the fissure are impalpable; in fully established cases, a
characteristic crater which feels like a vertical buttonhole can be palpated. The diagnosis must be established beyond doubt, for which a general
anaesthetic may be required.
Differential
diagnosis
Carcinoma of the anus in its very early stages
easily simulates a fissure. If real doubt exists, the lesion must be excised
under general anaesthesia and submitted to histological examination.
Multiple
fissures in the perianal skin are commonly seen as a complication of skin
diseases, scratching and inflammatory bowel disease, as well as homosexual
practices (sodomy, fluting and the use of anorectal sex toys; Fig.
60.8) and
anorectal sexually transmitted disease such as herpes. Admitted homosexuals,
should, after appropriate counselling, be offered a human immunodeficiency virus
(HIV) test as they may have acquired immunodeflciency syndrome (AIDS) (Chapter 9).
Tuberculous
ulcer has an undermined edge.
Proctalgia
fugax (see below) causes severe episodic pain.
Treatment
The pain of an anal fissure is so great that
usually the patient demands relief, and consequently many patients with an acute
fissure present early. The object of all treatment for this condition is to
obtain complete relaxation of the
internal sphincter. Provided the complications are dealt with, the fissure will
slowly heal as soon as all spasm has disappeared.
Conservative
treatment
Because of the risks of incontinence
associated with sphincterotomy, it is now usual practice to treat anal
fissures conservatively in the first instance using a chemical sphincterotomy.
Nitric oxide has been shown to be the neurotransmitter which induces relaxation
of the internal sphincter. 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 (Scholefield). In addition, glyceryl trinitrate ointment
improves blood flow to the area, and this aids healing. Unfortunately, glyceryl
trinitrate ointment may produce severe headaches and other agents with fewer
side effects should be available soon. 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. Anal dilators used in conjunction
with xylocaine ointment are difficult to insert because of pain and are rarely
effective.
Operative
measures. The simplest procedure in the past has been gentle dilatation of the
sphincter. Under general anaesthesia, the index and middle finger of each hand
were inserted simultaneously into the anus and carefully pulled apart dilating
the anus so that its diameter was no greater than four finger breadths. Great
care and judgement had to be exercised, so that the anal sphincter was not
overstretched. The risks of incontinence following this procedure have now made
it unpopular. Although it might still be used for young men with high pressure
sphincters who understand the slight risk, it is definitely contraindicated in
those patients with weak sphincters.
Should
these measures prove ineffective, or if the fissure is chronic with fibrosis, a
skin tag or a mucous polyp, then surgical measures are advisable. General
anaesthesia is best, although some surgeons use a local anaesthetic in the form
of xylocaine or lignocaine introduced into the ischiorectal fossa on each side,
in order to anaesthetise the nerves passing towards the rectum. In other
situations, a caudal anaesthetic is suitable.
Lateral
anal sphincterotomy (Notaras).
In this operation, the internal sphincter is divided away from the fissure
itself — usually either in the right or the left lateral positions. The
procedure can be done by an open or a closed method. Healing is usually complete
within 3 weeks. The operation is more successful for acute than chronic
fissures. Seventy-five per cent of cases are suitable for treatment by this
method, which can be done as an out-patient procedure under local anaesthesia by
an experienced surgeon. However, there is a definite yet small risk of
incontinence and it is imperative that patients are appraised of this risk
preoperatively.
Dorsal
fissurectomy and sphincterotomy. The essential part of the
operation is to divide the transverse fibres
of the internal sphincter in the floor of the fissure. If a sentinel pile is
present, this is excised. The ends of the dividend muscle retract and a smooth
wound is left. The after-treatment consists of attention to bowels, a daily bath
and the passage of an anal dilator until the wounds have healed, which usually
takes about 3 weeks. Despite the presence of the wound, there is little or no
pain and the results are good. The disadvantage of this operation is the
prolonged healing time — usually not less than 3 weeks and often longer —
and, occasionally, a mild, persistent and permanent mucus discharge. It is now
reserved only for the most chronic or recurrent anal fissures, the majority
being treated by lateral sphincterotomy. Once again incontinence might be a
postoperative complication.
Hypertrophied
anal papilla
Anal papillae occur at the dentate line, and
are remnants of the ectoderma) membrane that separated the hindgut from the
proctodaeum. As these papillae are present in 60 per cent of patients examined
proctologically, they should be regarded as normal structures. Anal papillae
can become elongated, as they frequently do in the presence of an anal fissure.
Occasionally, an elongated anal papilla may be the cause of pruritus. An
elongated anal papilla associated with pain and/or bleeding at defecation is
sometimes encountered in infancy. Haemorrhage into a hypertrophied anal papilla
can cause sudden rectal pain. A prolapsed papilla may become nipped by
contraction of the sphincter mechanism after defecation. Occasionally, a red
oedematous papilla is encountered with local pain and a purulent discharge from
the associated crypt. This condition of `cryptitis’ may be cured by laying
open the mouth of the infected anal gland and removing the papilla.
Treatment.
Using a slotted proctoscope, elongated papillae without haemorrhoids should be
crushed and excised after injecting the base with local anaesthetic. When large
papillae complicate internal haemorrhoids, this is an indication for operative
treatment of the haemorrhoids, as well as excision of the elongated papillae.
Proctalgia
fugax
This disease is characterised by attacks of
severe pain arising in the rectum, recurring at irregular intervals and
apparently unrelated to organic disease. The pain is described as cramp-like,
often occurs when the patient is in bed at night, usually lasts only for a few
minutes and disappears spontaneously. It may follow straining at stool, sudden
explosive bowel action or ejaculation. It seems to occur more commonly in
patients suffering from anxiety or undue stress, and also it is said to afflict
young doctors. The pain may be unbearable — it is possibly due to segmental
cramp in the pubococcygeus muscle. It is unpleasant, incurable, but fortunately
harmless and gradually subsides. A mote chronic form of the disease has been
termed the ‘levator syndrome’ and can he associated with severe
constipation. Biofeedback techniques have been used to help such patients: some
surgeons have been willing to sever the puborectalis muscle, but this can cause
incontinence.