Case

Mrs JS is a 35-year-old woman who presents with severe anal pain on defecation. The pain had worsened over the previous 6 months. On further questioning she admitted to straining at stool, and the stool was sometimes hard and pellet-like. Her pain occurred spontaneously when sitting but was greatly exacerbated while passing a stool and lasted up to an hour. As a result, she was reluctant to pass stool and often held back passing a motion for 2 or 3 days. She noted bright blood on the toilet paper intermittently. She had also noted a small swelling at the anus but was not aware of any prolapse during defecation. She had a background history of two normal vaginal deliveries, without a perineal tear or episiotomy. She was otherwise fit and healthy. Abdominal examination was normal. On anal examination there was a fissure posteriorly in the midline with a sentinel tag. On gentle digital examination she was exquisitely tender posteriorly just within the anal verge, and no further internal examination or proctoscopy was carried out. There was no perianal inflammation, swelling or tenderness.

Diagnosis: The history of severe acute anal pain usually suggests an anal fissure or perianal abscess (or other abscess, such as intersphincteric or ischiorectal). The finding of localised tenderness in the posterior midline within the anal canal is almost certainly due to a fissure. Haemorrhoids do not cause severe pain unless the haemorrhoids are thrombosed, in which case there are obvious prolapsed tender haemorrhoids on anorectal examination. Although haemorrhoids are more common than anal fissures overall, prolapsing haemorrhoids that are not acutely thrombosed cause slight discomfort only; the most common cause of severe pain is anal fissure.

Management and progress: First-line management is with dietary changes. The patient was commenced on a high fibre diet (of at least 30 g per day), supplemented with additional fibre such as psyllium (Metamucil™), with at least 1.5 L of water, to soften her stools. She was treated with glyceryl trinitrate (GTN) 0.2% cream (Rectogesic™) placed into the lower anal canal twice daily. She developed a troublesome headache after application of the cream. She was instructed to then reduce the amount used to the point where headaches do not occur, to continue with that dose for 2 or 3 days and then gradually increase to the recommended dose (the body adjusts to the lower dose, and the higher dose is subsequently tolerated, by the process of tachyphylaxis).

Her pain improved considerably, but she returned 6 weeks later complaining of a recurrence of severe pain. She had successfully softened her stool and had complied with use of the GTN for 4 weeks to allow the fissure time to granulate.

She was then progressed to the next line of treatment, which is injection of Botox®. This was carried out in hospital under sedation. A full digital examination and flexible sigmoidoscopy was also carried out to exclude other causes of pain and bleeding, and at the examination there were no signs of proctitis or other mucosal pathology, and no intersphincteric or other perianal sepsis.

The fissure healed and her symptoms resolved. However she again returned after 3 months with a recurrent fissure, producing sufficient pain to cause her to miss days off work. She was advised to undergo lateral sphincterotomy, after providing clear information about the small risk of permanent faecal incontinence (usually minor). After undergoing anal manometry and endoanal ultrasound to confirm that anal sphincter function had not been affected by her vaginal deliveries (and hence place her at increased risk of incontinence after sphincterotomy), she underwent sphincterotomy under general anaesthetic. The fissure healed fully, with complete resolution of pain.

Introduction

Perianal pain may be a mild discomfort, an acute severe pain, or a chronic debilitating symptom. The nature of the pain and any associated symptoms will provide important clues to the cause. Important points are the severity of the pain, the duration of the pain, the relationship of pain to defecation, and associated bowel symptoms such as rectal bleeding, prolapse at the anus, or discharge of pus.

The causes of perianal pain are listed in Box 12.1.

History

A patient presenting with severe unrelenting pain over recent hours to days, not related to defecation, is likely to have either perianal sepsis or thrombosed haemorrhoids. These patients are usually totally distracted from other activities by the pain. While thrombosed haemorrhoids cause severe, acute pain, non-thrombosed haemorrhoids are usually not associated with pain although there can be discomfort during defecation if the haemorrhoids prolapse.

Typically the pain from an acute anal fissure is severe and is precipitated by defecation; it may take minutes to hours to gradually settle. The pain associated with pruritus ani is annoying but not severe, and is usually associated with the presence of faecal soiling over a raw area.

The pain of anal fistula tends to be mild and associated symptoms are perianal discharge or bleeding. The pain of proctalgia fugax is very typical: sudden onset of a severe, dull rectal ache, often waking the patient from sleep, sometimes causing a desire to defecate, and lasting 15–20 minutes. There may be long periods without any pain. There are a number of chronic perianal pain syndromes associated with a vague dull ache.

The presence of associated bowel symptoms or systemic symptoms may clearly point to the diagnosis. The patient should be asked about rectal bleeding. There may be minor perianal bleeding with anal fissure, usually apparent on the toilet paper after defecation or occasionally on the surface of the stool. With internal haemorrhoids, bleeding can be a more prominent feature than pain; the bleeding tends to be related to defecation and is most commonly noted on the toilet paper or in the toilet bowl. Pruritus ani can be associated with minor bleeding associated with wiping the perianal region after defecation. Perianal abscess is not usually associated with bleeding unless the abscess has discharged spontaneously or has been drained. There may be a minor degree of perianal bleeding with anal fistula. There should not be significant rectal bleeding with any of the chronic pain syndromes or with proctalgia fugax.

Symptoms of constipation are commonly associated with a number of painful perianal conditions (Ch 11). In some cases the constipation leads to the condition, such as fissures or haemorrhoids, but in other cases of anal fissures or thrombosed haemorrhoids the constipation may be caused by the patient’s reluctance to defecate because it induces or exacerbates pain. The conditions causing perianal pain should not themselves be associated with diarrhoea. Therefore, the presence of diarrhoea suggests another disease process (e.g. Crohn’s disease).

Examination

Fissure-in-Ano

Pathology

The acute fissure is a superficial split with soft edges.

A chronic fissure evolves through several phases:

• superficial—longitudinal muscle fibres of musculus submucosae ani may be seen in the base;

• deeper fissure—the edges may be indurated; transverse fibres of internal sphincter are seen;

• advanced fissure—edges are indurated and may be undermined; a skin tag (sentinel pile) develops at the lower edge; a fibroepithelial polyp (hypertrophied anal papilla) may form at the upper end of the fissure at the dentate line (see Fig 12.1);

Figure 12.1 Chronic anal fissure. Note the deep chronic posterior fissure with skin tag below and fibroepithelial polyp above.

Finally, an abscess may form in the submucosal plane or in the skin tag leading to a superficial fistula, or between the internal and external sphincters (intersphincteric).

Secondary fissures may be broad or long. If a fissure extends into the upper anal canal above the dentate line, it is usually a secondary fissure. These are sometimes called anal ulcers.

Anal Sepsis

The majority of cases of anal abscess develop from a primary infection in an anal gland (Box 12.2). This infection results in the formation of an abscess in the intersphincteric space, which in turn may spread to form a perianal abscess, ischiorectal abscess or supralevator abscess. If an abscess communicates with the anal canal, and also discharges or is surgically drained through the perianal skin, a fistula has formed. Anal abscess and fistula are therefore part of the same pathological process.

Pathology

Primary anal gland (cryptoglandular) abscess and fistula

Infection in an anal gland starts after faecal bacteria gain entry via the anal duct, resulting in an intersphincteric abscess. This may then spread:

• downwards to the perianal skin to form a perianal abscess;

• upwards to the supralevator region to form a supralevator abscess;

• laterally along the longitudinal muscle strands that penetrate the external sphincter, or down and around the lower edge of the internal sphincter, in both cases to reach the ischiorectal fossa to form an ischiorectal abscess.

See Figures 12.2A and 12.2B.

Figure 12.2A Spread of anal infection. Infection starts in an anal gland and leads to an intersphincteric abscess. This may spread downwards, upwards, or outwards across the external sphincter.

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Figure 12.2B Spread of anal infection. As a result of this spread, an abscess forms in a perianal, supralevator or ischiorectal position.

From Gordon PH, Nivatvongs S. Principles and practice of surgery for the colon, rectum and anus. 2nd edn. Montreal: Routledge/Taylor & Francis Group; 2002, with permission.

An intersphincteric, ischiorectal or supralevator abscess may spread circumferentially to form a ‘horseshoe’ abscess.

Microbial culture of pus from an anal abscess yields gram-negative organisms and anaerobic organisms (mainly Bacteroides spp.) originating from the bowel.

A cryptoglandular abscess should be distinguished from:

• an abscess originating in the perianal skin from infection in a hair follicle—culture of pus shows skin flora, particularly Staphylococcus aureus, and the abscess is never associated with an anal fistula;

• hidradenitis suppurativa—apocrine sweat glands are found in the axilla, groin, areola and perianal region; infection may result in abscess and chronic sinus formation; and

• pilonidal sinus—a pilonidal sinus usually occurs in the natal cleft, beginning as an ingrown hair, which results in a chronic infection in the subcutaneous tissues. Occasionally, a pilonidal sinus may occur in the perianal region and appear very similar to a true cryptoglandular abscess or fistula.

A cryptoglandular abscess may progress to form a fistula of the following type:

• intersphincteric fistula (45% of fistulae): this forms from a perianal abscess which discharges spontaneously through the perianal skin or is surgically drained through the perianal skin to form a communication between the skin and the anal canal (Fig 12.3);

• trans-sphincteric fistula (35%): this forms in a similar way to an ischiorectal abscess. The fistula encloses a variable amount of external sphincter muscle, and the amount of muscle enclosed will determine the correct surgical treatment (Fig 12.4);

• suprasphincteric fistula (15%): this forms when a supralevator abscess discharges downwards through the levator ani muscle into the ischiorectal fossa and then through the skin (Fig 12.5);

• extrasphincteric fistula (3%): in most cases there is a history of attempted surgical drainage of a fistula. Iatrogenic damage results from probing an ischiorectal abscess or trans-sphincteric fistula, creating a passage into the rectum instead of along the correct course into the anal canal. Very rarely an extrasphincteric fistula results from spontaneous discharge of a rectal or sigmoid abscess resulting from diverticular disease, Crohn’s disease or from perforation of the bowel by a fish or chicken bone (Fig 12.6);

• subcutaneous fistula (2%): this is a superficial fistula that begins as an abscess in an oedematous skin tag usually associated with an anal fissure. The abscess discharges through the mucosa of the lower anal canal and through the perianal skin to form a small subcutaneous fistula.

Figure 12.3 Intersphincteric fistula—infection does not cross the external sphincter. Perianal abscess (left) results in the fistula (right). Note that the fistula opens internally in the anal canal at the position of the infected anal gland at the dentate line.

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Figure 12.4 Trans-sphincteric fistula—infection crosses the external sphincter to form an ischiorectal abscess (left), which then discharges to form the fistula (right).

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Figure 12.5 Suprasphincteric fistula—infection spreads upwards in the intersphincteric plane to form a supralevator abscess (left), which discharges downwards through the levator ani to reach the ischiorectal fossa and then through the skin to form a fistula.

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Figure 12.6 Extrasphincteric fistula (right)—develops from a trans-sphincteric fistula that is incorrectly probed so that the probe is pushed upwards through the levator ani into the rectum. Rarely the fistula forms spontaneously from pathology in the rectum (left).

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Secondary abscess and fistula

The features of these are as follows:

• inflammatory bowel disease: Crohn’s disease is the most common cause of secondary abscess formation, which in turn may lead to fistula formation. Complicated, circuitous or multiple fistulae may form. Ulcerative colitis is a less common cause.

• leucopenia: leukaemia or other cause of pancytopenia may result in anal sepsis. Pain and spreading perianal infection occur. Since there is a paucity of white blood cells, an abscess does not form. Treatment is therefore with antibiotics rather than surgical drainage.

• immunosuppression: AIDS or drugs causing immunosuppression predispose to infection in the anal glands, with abscess and fistula formation.

• infection: tuberculosis, actinomycosis and occasionally threadworm infestation may cause abscess formation.

• trauma: trauma to the rectum by a penetrating injury, or by insertion of a sharp object per anum, may pierce the rectum and cause a supralevator abscess and extrasphincteric fistula.

• rectal carcinoma: advanced rectal cancer may undergo tissue necrosis and abscess formation, usually in the ischiorectal fossa. Another rare variety of malignant fistula occurs when a rectal cancer seeds malignant cells into an established primary fistula.

• diabetes mellitus: the incidence of diabetes mellitus is higher in patients with anal sepsis than in the rest of the population. Occasionally, anal sepsis is the presenting feature of occult diabetes.

Clinical features

The cardinal feature of an anal abscess is severe pain. A perianal abscess usually causes a tender red swelling near the anal verge (see Fig 12.7).

Figure 12.7 Perianal abscess

An ischiorectal abscess is placed more deeply and there is usually less tenderness and swelling, but there may be high fevers if the abscess is large. An intersphincteric abscess produces marked tenderness on digital examination of the anal canal.

Usually the external opening of a fistula is easily identified. The position should be noted in order to predict where the internal opening will be found (see Fig 12.8).

Figure 12.8 Goodsall’s rule—a posterior fistula passes around to open internally at the posterior midline. An anterior fistula passes radially to open directly at a corresponding internal position.

From Goligher JC, Duthie HL, Nixon HH. Surgery of the anus, rectum and colon. 4th edn. London: Baillière Tindall; 1980, with permission.

Supralevator extension is easily palpated on digital examination (see Fig 12.9).

Figure 12.9 Supralevator induration is palpated on rectal examination. This indicates proximal extension of an abscess or fistula, and should raise suspicion of a suprasphincteric fistula.

From Parks AG, Gordon PH, Hardcastle JD: A classification of fistula-in-ano. Br J Surg 1976; 63(1):1–12, with permission.

Principles of surgical treatment

Incorrect surgical treatment of anal sepsis can have devastating consequences, with faecal incontinence resulting from division of excessive amounts of sphincter muscle. An abscess requires immediate drainage. This is best done under general anaesthetic, both for patient comfort as well as to optimally assess the extent of the abscess. An internal opening is found in 30–50% of cases. If an internal opening is not present and culture of pus yields a growth of Staphylococcus and other skin flora, no further treatment is needed. If bowel flora are cultured, an internal opening may be present and examination under anaesthesia should be carried out 10–14 days later. If an internal opening is present at the time of abscess drainage, the fistula should be laid open (fistulotomy).

An intersphincteric or trans-sphincteric fistula can be laid open if there is sufficient muscle remaining above the fistula track. If the track is too high, or if it is suprasphincteric or extrasphincteric, it should be treated either by placing a flap of mucosa and internal muscle to close the internal opening of the fistula, or alternatively with a Seton technique, where a rubber drain is placed around the fistula and gradually tightened (Fig 12.10).

Figure 12.10 Anterior anal fistula. The external opening was at the top end of the wound near the surgeon’s finger; the fistula has been incised down towards the anal verge; a rubber Seton has been placed through the high trans-sphincteric fistula since the fistula enclosed too much muscle to be safely divided.

The use of curettage and injection of fibrin glue, or plugs made from pig small bowel mucosa, will heal 20–30% of fistulas. While the long-term healing rate of these techniques may be low, they are safe as they do not affect continence.

Recurrent fistulae require careful assessment under anaesthesia, as well as endoanal ultrasound or magnetic resonance imaging (MRI) to help identify tracks that have not been detected during initial surgical treatment. Underlying inflammatory bowel disease should be excluded.

Haemorrhoids

Haemorrhoids (also known as piles) are usually a painless condition and, although haemorrhoids may cause discomfort during prolapse, severe anal pain should not be attributed to haemorrhoids unless the haemorrhoids are found to be acutely thrombosed.

Clinical features

Bleeding

Bleeding is the most common symptom. The blood is bright red and noted on the toilet paper. When the haemorrhoids prolapse externally beyond the hypertonic internal sphincter there may be a large amount of blood dripping into the toilet bowl during defecation. Occasionally, there may be streaks of blood on the surface of the stool, but this symptom should always raise suspicion of more serious rectal pathology. When the haemorrhoids are continuously prolapsed, spontaneous bleeding unrelated to defecation may occur with blood seeping through to the clothes. Anaemia uncommonly results from haemorrhoidal bleeding, but may occur with profuse or frequent bleeding over a prolonged period.

Prolapse

Haemorrhoids are classified according to the degree of prolapse of the anal cushions:

• first degree: prolapse within the anal canal so that the subject is not aware of any external prolapse. Bleeding is the only symptom;

• second degree: prolapse outside the anal canal on defecation, with spontaneous reduction immediately after defecation;

• third degree: prolapse that requires manual reduction. If the patient does not reduce the haemorrhoids, they may remain external for up to some hours and then reduce spontaneously (see Fig 12.11);

• fourth degree: haemorrhoids that cannot be reduced.

Figure 12.11 Prolapsed third-degree (manually reducible) haemorrhoids.

Discomfort

External prolapse of large haemorrhoids may cause discomfort. There may be further discomfort when attempting to reduce the haemorrhoids. Severe pain is experienced only if thrombosis occurs.

Thrombosed haemorrhoids

Prolapse beyond the anal sphincter may result in thrombosis. There is swelling and severe pain. The prolapsed haemorrhoids are easily visible and very tender (see Fig 12.12).

Figure 12.12 Irreducible fourth degree haemorrhoids. Note the left lateral pedicle (centre), which is thrombosed.

If thrombosed haemorrhoids are not treated surgically there is usually gradual resolution, but pain may persist for up to 2–4 weeks. Necrosis and infection may result. Most patients will be treated symptomatically with stool softeners and oral (non-constipating) medications, and once the thrombosed sections have resolved rubber banding to the internal haemorrhoids should be carried out, usually after 6–8 weeks (see below). Occasionally, thrombosed haemorrhoids may return into the anal canal and are not visible externally, but if thrombosis is established, severe pain persists and a tender lump is palpated on digital examination.

Incontinence

Minor seepage of faeces or mucus may occur. The perianal skin may become excoriated with resulting pruritus and pain.

Pruritus Ani

Pruritus ani is a common condition varying from mild itching to severe intractable itching and pain. The true prevalence is unknown since many sufferers do not seek medical advice, but one study in Birmingham found that 45% of people surveyed had symptoms of pruritus within a 5-year period.

Management

Pruritus ani is a difficult condition to treat and several steps must be followed if success is to be achieved:

1. A careful history about symptoms of local pathology and faecal seepage should be obtained. Examination for local pathology is made and any condition that predisposes to seepage is treated. Threadworms are seen at the anal verge or in the anal canal and are treated with a single dose of pyrantel.

2. If the skin is excoriated scrapings are obtained for microscopic examination and culture. A scalpel blade is used and several scrapings are placed onto a glass slide, which is then sealed in a container. If Candida is present, topical nystatin cream is used. Tolnaftate is used for tinea.

3. If there has been a recent change to nylon underwear or a change of washing powder or bath soap, these should be eliminated as a cause.

Figure 12.13 Thrombosed external haemorrhoid. Note how it is confined to a small area, compared with thrombosed internal haemorrhoids.

4. If no predisposing cause is found, idiopathic pruritus ani is present. Vigorous efforts at perianal hygiene are needed since collection of moisture in the area, often unrecognised by the patient, is sometimes present. Washing the area once or twice daily may not be adequate. Washing may need to occur at least three or four times daily. Thereafter, the area is dabbed dry (Box 12.3). Recent studies have shown that improvement of symptoms can be achieved with the use of intradermal injection of methylene blue in resistant cases of idiopathic pruritus ani.

Box 12.3 Instructions to patients with anal irritation (pruritus ani)

1. The area must be kept clean and dry. This means cleaning as instructed below at least twice during the day and once at night, and after every bowel action. It is not sufficient to clean once or twice a day only.

(a) Use soft toilet paper only.

(b) Wipe the area with cotton wool and warm water. ‘Baby wipes’ without alcohol can be used if preferred.

(c) Gently dab the area completely dry with soft toilet paper.

(d) Apply the prescribed cream only, for the length of time indicated. At the end of that period, apply a zinc oxide powder to the area in place of the cream. Do not use other powders, or any cream or ointment unless prescribed by your doctor.

2. Use a pH-balanced soap for bathing or showering.

3. Do not scratch the skin. If irritation is severe, pinch the skin outside the clothes.

4. If there is minor seepage of mucus or bowel motion, report this at your next visit.

5. Continue treatment strictly for 3 months after the itching stops. If the symptoms recur recommence treatment.

Chronic Perianal Pain Syndromes

There are a number of conditions of uncertain aetiology that produce chronic perianal and pelvic pain. They may produce significant morbidity, and treatment is often unsuccessful.

Key Points