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Anal fissures

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Anal fissures are a common cause of perianal pain that has been a source of frustration to man and their physicians for thousands of years. The symptoms of pain and bleeding on defecation are very often erroneously attributed to hemorrhoidal disease, even by physicians themselves. It represents about 10 to 15% of referrals to any colorectal practice. This issue of S-files aims to describe the fundamental pathophysiology of anal fissures, the investigational process to adopt when managing a patient with suspected fissures and the evidence-based efficacy of treatment modalities that are currently available.

What are Anal fissures

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An anal fissure is essentially a tear or split in the anoderm at the dentate line. 80-90% of these are located in the posterior midline. Anterior midline locations are far less common, occurring in 5-10% of all cases. Symptoms of anal fissures often arise soon after the passage of a hard bowel movement through the anal canal. This is believed to cause stretching and subsequent tearing of the anoderm. Occasionally, this may be associated with a bout of severe diarrhea. The anterior and posterior midlines are the weakest areas of the anal canal. It is at these locations that the external sphincter fibers decussate. In addition, the midline locations are areas where the skin is tethered more adherently to the sphincter complex. During the process of defecation, partial eversion of the anal canal leads to more tension arising in these areas. Coupled with the less adequate anodermal blood flow here, ischemia occurs and results in an ulcer being formed.

Once a fissure has formed, a cycle of repeated injury results. The resulting internal anal sphincter spasm tends to hold the edges of the ulcer apart, thereby preventing wound healing. Instead, further tearing of the mucosa tends to result with each bowel movement.

Only 2-5% of fissures are located in other locations and these should be viewed with suspicion. Common etiologies of these fissures include Crohn's disease, ulcerative colitis and chronic infective processes such as anal tuberculosis, HIV infection and cancer. Patients who present with such atypical fissures should be referred to a colorectal surgeon for further evaluation. Biopsies of these fissures are mandatory.

How does one examine a patient with perianal pain and suspected anal fissures?

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Patients are placed in a left lateral position with both hips and knees flexed towards the chest. Adequate lighting is mandatory. Simple spreading of the buttocks will easily reveal the distal anal canal and the fissure or ulcer complex. It is often not possible to perform an anoscopic examination in these patients and this is not recommended. The classical pain arising from the fissure can be elicited by using a cotton-tipped swab stick to stroke the fissure bed.Fissure Examination

What do fissures really look like?

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Patients with anal fissures present with a very classical history of a 'searing' or 'tearing' type of pain which is associated with each bowel movement. This is usually accompanied by bright red per rectal bleeding. Symptoms of pruritus or perianal skin irritation may also be present.

Acute Anal Fissure

Fissure
This is a superficial tear in the vertical axis of the squamous lining of the anal canal. Located between the anal verge and the dentate line, these tears may deepen to expose the underlying internal anal sphincter.

Chronic Anal Fissure

A fissure which fails to heal after 4 weeks is considered chronic. These fissures will have developed secondary changes which include the following:

Sentinel tag - these are hypertrophic skin tags at the distal edge ofthe fissure and are very commonly mistaken as external hemorrhoids and hence the misnomer 'sentinel pile'
Hypertrophic anal papilla
Induration of the edge of the fissure
Fibrosis of the exposed internal anal sphincter fibres
Relative stenosis secondary to spasm

Sentinel Pile

It is imperative that the examining physician attempt to differentiate between anal fissures and hemorrhoids. Although this may be difficult at times, a properly performed physical examination of the perianal region is often revealing. Non prolapsing internal hemorrhoids can only be diagnosed through an anoscopic or proctoscopic examination. Attempting this in a patient with anal fissure is almost impossible without inflicting severe pain. Again, most fissures can be diagnosed by simple parting of the perianal skin.

Chronic Fissure

Adjunct Investigations

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Anal manometry

Studies have shown that patients with anal fissure demonstrate high resting pressures. This is the fundamental basis of

internal sphincterotomy as the surgical treatment of choice. Manometry is not used routinely in the evaluation process.However, it is extremely useful in evaluating patients with recurrent
recurrent fissures, elderly patients with pre-existing incontinence and multigravid women with possible pre-existing sphincter defects as this allows the surgeon to decide on the procedure of choice.

Manometery

Endoscopy

In patients who are below the age of 50 years, it is reasonable to allow for a trial of conservative or medical treatment before embarking on any endoscopic evaluation. However, persistence of symptoms warrants a sigmoidoscopic evaluation in this group of patients.

On the other hand, any patient above the age of 50 years who presents with per rectal bleeding should be offered a full colonoscopic evaluation before concluding that the symptomatology is fissure related.

CARET (Careful Assessment & Rapid Effective Therapy) Service

At the Colorectal Clinic, we offer a one-stop service that enables us to offer your patient a flexible sigmoidoscopy or a colonoscopy (as required) as part of our specialist consulation. If indicated, anal manometry or endoanal ultrasonography can be performed at the same consult. This service will provide immediate reassurance of the benign nature of the rectal bleeding.

Aspects of Treating Fissures

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The main goal of treatment is to interrupt the cycle of sphincter spasm and further tearing of the injured mucosa, thereby allowing the fissure to heal. This is carried out by advising the patient on the 4 pillars of treatment:

Regulation of stool consistency
Reduction of anal sphincter tone
Relief of discomfort, bleeding and pain
Allow healing of the fissure

These targets are achievable through a variety of measures that will be described.

What to Advise

This is an often overlooked component of treatment which cannot be overemphasized. All patients suffering from anal fissures should be encouraged to increase their intake of fluid and fiber. Stool softeners and sitz baths have virtually no side effects and often diminish the bleeding and pain. Additional comfort may be achieved with the use topical anesthetics such as 2% lignocaine. Fluid intake should be adequate and a minimum of 8 to 10 glasses of water is recommended especially in our tropical climate. Simple hygiene practices such as the use of moist tissues or baby wipes is often a better alternative to toilet paper after bowel movements. If possible, using a shower spray for cleaning the perineum and padding dry is recommended.
Dietary advice includes increasing one's intake of fresh fruits, vegetables and bran cereal. Additional fibre supplements are also very useful in maintaining soft bowel movements.

Sitz Baths - How to prepare them

These warm baths provide soothing comfort to patients suffering from anal fissures by relaxing the anal tone and relieving the pain. They are prepared by adding lukewarm water to a shallow tub with or without an added 2 tablespoon of salt. A duration of 15-20 minutes is usually sufficient.
Healing rates of up to 50% can be expected with the institution of such measures.

Medicines - Do They Work?

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The medical literature is filled with numerous studies addressing the efficacy of non-surgical treatments for anal fissures. It is therefore imperative that physicians be cognizant of the evidence that is available for each one of these. The following serves to summarize the treatment options the current available evidence on their efficacy.

The main intents of medical therapy are threefold:
To promote internal anal sphincter relaxation
To maintain the passage of soft stools in order to minimize further trauma to the mucosa around the fissure
To provide pain relief

Topical Nitrates

These have been shown to improve the local blood flow and reduce the pressure exerted by the internal anal sphincter, thereby increasing the likelihood of healing. These are prepared in the form of a glyceryl trinitrate (GTN) paste or ointment at a 0.2% concentration. Most pharmacies are able to custom prepare these on request. Alternatively, commercially available preparations e.g. Rectogesic are available. Application around the perianal skin 2 to 3 times a day usually suffices. Patients must be warned of the reported 20-30% incidence of headaches as a side effect. These commonly occur about 30 minutes following application. In addition, patients on Sildanefil (Viagra) should avoid this form of treatment in view of the increased risk of hypotension. The comprehensive Cochrane review has found that the success rates of topical nitrates are only marginally better than placebo in the management of chronic anal fissures.

Topical Calcium Channel Blockers

These act mainly by reducing the internal anal sphincter pressure. Healing rates of 65-95% have been reported by several studies. Nifedipine and diltiazem(2%) are the 2 main topicals that have been studied. The advantages of these when compared to the topical nitrates are the lower incidences of headaches as a side effect. The efficacy of these agents has been shown to be equivalent to nitrates but there is currently insufficient data to conclude if they are superior to even placebo in healing fissures.

Botox for the other end

Injection of botulinum toxin into the internal anal sphincter results in what is commonly known as 'chemical sphincterotomy'. The resulting effect of a reduction of the internal anal sphincter pressure lasts for 2-3 months, allowing the fissure to heal. Patients are informed of the possibility of transient incontinence to flatus, which occurs in 10%. 5% of patients will experience incontinence to stools transiently. Failure rates of 20% have been reported.
This procedure is performed in the Colorectal Clinic under endoanal ultrasonographic guidance. Again, like the topicals, the data available does not show any significant advantage in efficacy when compared to the nitrates. However a single injection translates to convenience over the need for thrice daily topical applications of ointments.

Surgery to ease the pain

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This is indicated when a trial of medical treatment has failed to produce any significant healing of the fissure, which is most commonly manifested as a persistence of pain. The goal of this is once again, to effect relaxation of the internal anal sphincter. This is achieved by an internal sphincterotomy, which essentially involves the surgical division of the internal anal sphincter from its distal most end to the level of the dentate line, or the most proximal limit of the fissure. The procedure is routinely performed as a day case, with the patient under either general or regional anesthesia. It is performed through a small incision at the anodermal junction overlying the inter-sphincteric groove. This incision is placed laterally to avoid what is known as a keyhole deformity, hence the term lateral internal sphincterotomy.

The lateral internal sphincterotomy is the treatment of choice for anal fissures with success rates in excess of 90%. Symptom improvement is usually dramatic and a median of 2-3 weeks is usually required for total resolution of symptoms. The major concern with the procedure is the risk of fecal incontinence. Although about 40% of patients will report some degree of incontinence in the first week, either to flatus or stools, studies have shown that only about 5% will suffer from mild incontinence to flatus 1 month post-operatively. Quality of life scores have been reported to be consistently good in patients following lateral internal sphincterotomy.

Sphincterectomy
Nevertheless, in view of these risks, patients who have had a history of anorectal surgery and multiparous women should only be offered lateral internal sphincterotomy with caution. At the Colorectal Clinic, we routinely perform anal manometry and endoanal ultrasonography in these patients prior to surgery.

Recurrent anal fissures and alternative procedures

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In patients who have had a previous history of internal sphincterotomy, or who have poor sphincter function, an alternative procedure is typically offered. These include advancement flaps or fissurectomy with or without adjunct medical treatments such as botulinum injection and topicals. Evaluation by a colorectal surgeon is recommended in these group of patients.

Take-home points

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Bleeding from anal fissures are commonly and erroneously attributed to hemorrhoids. Anal fissures are associated with pain. Hemorrhoidal bleeding is usually painless.
Most acute fissures will heal with conservative measures.
General advice include fluid intake, ensuring soft consistency of stools and symptomatic relief with topical anesthetics and analgesics.
Medical therapy is a good option for acute fissures although the efficacy and complication rates are variable.
Most patients with chronic anal fissures will require surgical treatment, which have excellent results. These are routinely performed in a day surgery setting.
Recurrent fissures should be evaluated by an experienced coloproctologist with adjunct investigations such as anal manometry and endoanal ultrasonography before deciding on the appropriate therapy.
Atypically located fissures must be biopsied.

Doctors

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Associate Professor Tan Ker Kan
Dr Cheong Wai Kit
Assistant Professor Bettina Lieske
Dr Ian Tan
Dr Norman Lin
Dr Lee Kai Yin

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2023/08/22