Anal Pain

D Z Lubowski. Perianal Pain. In: Clinical Gastroenterology (Talley NJ, Martin CJ, Editors), McLennan and Petty, Sydney 1996, ppl8l-203, (copyright 1996 Sydney, Elsevier Australia, Talley and Martin, Clinical Gastroenterology)

CLINICAL APPROACH
In a patient presenting with perianal pain, the critical lines of questioning are:
1. the severity of the pain;
2. the duration of the pain;
3. whether the pain has been constant or fluctuating;
4. relationship of pain to rectal evacuation; and
5. associated bowel symptoms (eg rectal bleeding).

The important causes of perianal pain are listed in Table 11.1.

HISTORY
A patient who presents with severe unrelenting pain over recent hours to days is likely to have either perianal sepsis or thrombosed haemorrhoids. These patients are usually totally distracted from other activities by the pain. Some patients will complain of episodic severe perianal pain with intervening periods without pain.

Typically the pain from an acute fissure-in-ano is severe and is precipitated by defecation; it may take minutes to hours to gradually settle. Thrombosed haemorrhoids cause severe, acute pain, while non-thrombosed haemorrhoids are usually not associated with pain. The pain associated with pruritus ani can be moderately severe. The pain is specifically associated with the presence of faecal soiling over a raw area and is relieved by effective cleaning of the soiled surface.

The pain of anal fistula tends to be mild, dull and aching. Associated symptoms such as discharge or leakage of pus perianally are clues. The pain of proctalgia fugax is of short duration, usually lasting minutes with a rapid onset over seconds and resolution over minutes. There are long periods without any pain. There are a number of chronic perianal pain syndromes associated with a vague dull throbbing ache.

The presence of associated bowel symptoms or systemic symptoms may clearly point to the diagnosis. Ask about any rectal bleeding. There may be minor perianal bleeding with fissure-in-ano, usually apparent on the toilet paper after defecation or occasionally on the bowel motion. 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 after wiping (haematochesia). Pruritus ani can be associated with minor bleeding associated with wiping the perianal region with paper after defecation. Perianal abscess should not be associated with bleeding unless the abscess has erupted 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 (Chapter 10). This is because in some cases patients are reluctant to defecate because it induces or exacerbates pain. This can occur with a fissure-in-ano or thrombosed haemorrhoids. Excessive straining can also cause a fissure in some cases. The conditions causing perianal pain should not themselves be associated with diarrhoea. Therefore, the presence of diarrhoea suggests another disease process (eg Crohn's disease).

EXAMINATION
Inspection
While the history will commonly give vital clues as to the cause of the perianal pain, local examination will usually confirm the diagnosis. The examination clearly needs to be focused in the perianal region. A general abdominal examination, however, is also necessary.

The easiest and most comfortable position for inspection is with the patient in the left lateral position with the hips and knees flexed. The buttocks are parted with gentle pressure from the palm of the hand so that the perianal skin can be closely scrutinised. Red excoriated, weeping skin suggests that the pain is due to pruritus ani. The presence of a sinus means an anal fistula should be sought. The presence of a spot of pus or blood in the perianal region, particularly if this returns after a gentle wipe, can point one to the external opening of a fistula. A perianal abscess can be associated with a perianal swelling depending upon the proximity of the abscess to the external skin. The skin over an abscess may be red, depending on the proximity of the abscess to the skin, and such swellings are usually diffuse and greater than 2 cm.

Just beyond the anal verge there might be irregular flaccid tags of skin which are asymptomatic but may be associated with underlying haemorrhoids. The presence of a small, tense, often bluish swelling, just beyond the anal verge is suggestive of a thrombosed external haemorrhoid. A fissure-in-ano is commonly not obvious on external examination except in very chronic cases because in the acute case the patient will not allow the buttocks to be parted sufficiently to allow adequate inspection because of the pain that is induced. A thrombosed internal haemorrhoid which has prolapsed may be evident at the anal verge as an oedematous 1-2 cm swelling.

Internal haemorrhoids are usually not apparent on external examination. The chronic pain syndromes are not associated with perianal stigmata on inspection.

Palpation
The features to be sought on palpation are:
1. the presence of a lump;
2. tenderness with or without an obvious palpable lump;
3. the presence of a sub-mucosal cord; and
4. associated abnormality of sphincter tone.

A perianal abscess which has presented as a perianal lump with associated overlying erythema will always be focally extremely tender. Focal tenderness to palpation also is present with thrombosed internal as well as external haemorrhoids.

The patient with an anal fissure will usually not tolerate perianal examination because of the pain. Gentle local pressure just lateral to the site where the fissure is thought to be will often elicit focal pain. This should be the limit of the examination in such cases without anaesthesia.

The perianal regions should be gently palpated looking for a subcutaneous or submucosal cord leading from the ostium of an anal fistula. This cord will be followed internally and its position in relation to the anal sphincter should be noted.

Deeper rectal examination may demonstrate focal tenderness associated with abscess formation in the ischiorectal fossa. If the cause of the perineal pain is not clear at this stage, gently rocking the coccyx with posterior pressure may elicit sharp pain suggesting the diagnosis of coccygodynia. None of the conditions that causes chronic perianal pain is associated with an abnormality of sphincter function on digital rectal examination.

If an adequate rectal examination is not possible. because of perianal pain, then it is appropriate to perform this examination under anaesthesia. Given the risks associated with anaesthesia, this examination should be performed by an experienced person capable of dealing with any perianal pathology found at that examination.

Proctoscopy
Proctoscopy will be possible in an office setting for most of these patients (Chapter 20). It may not be possible in patients with a fissure-in-ano, anal abscess or thrombosed haemorrhoids. Proctoscopy will allow a diagnosis of internal haemorrhoids which will become more prominent or evident as the proctoscope is withdrawn.

Sigmoidoscopy
This examination, although commonly performed, usually adds little additional information in these cases unless more proximal bowel disease is suspected, based on the history.

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 found that 45% of people surveyed had symptoms of pruritus within a five-year period.

Aetiology
In a minority of cases a definite cause is found. The majority of cases are idiopathic. In those cases where the perianal skin is cracked and excoriated, the cause for the itch and pain is obvious; but in many cases the perianal skin appears normal and the precise cause for the itching is unknown.

Predisposing causes
Faecal seepage. Minor degrees of soiling may cause irritation of the perianal skin. Underlying anal pathology such as haemorrhoids, mucosal prolapse or anal fissure should be identified and treated. Some patients are not aware that minor seepage is occurring.

Anal disease. Primary anal conditions must always be excluded. These include anal warts, skin tags, haemorrhoids, fissure, fistula, anal cancer, Bowen's disease, and generalised skin conditions such as eczema and psoriasis which may also affect the perianal skin.

Infection. Organisms known to be associated with pruritus ani include:
• fungi - Candida albicans, tinea;
• bacteria - Corynebacterium minutissimum;
• parasites - threadworm (Enterobius vermicularis), a common cause in children but a rare cause in adults.

Allergy. Hypersensitivity of the perianal skin may result from:
• topical creams or suppositories containing steroids or local anaesthetic agents;
• underwear, particularly nylon;
• washing powders for clothing.

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

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

Coccygodynia
This presents with an ache in the lower sacrum and coccyx. The pain may radiate to the buttocks and is worse on sitting. Eighty percent of cases are in women, usually over 50 years of age. Sometimes there is a history of trauma to the coccyx. X-ray findings are normal. Rocking the coccyx on rectal examination may elicit pain.

Treatment
Local points of tenderness are infiltrated with local anaesthetic; the injection of alcohol or phenol has been reported to be successful in up to 50% of cases. This treatment is best carried out in a specialised pain clinic. Coccygectomy is usually unsuccessful.

Proctalgia fugax
This is an unmistakable clinical condition, most commonly affecting young men, although it occurs at all ages, consisting of severe pain in the anal canal or slightly higher in the pelvis, lasting 5-30 minutes. It may occur during the day or night, sometimes waking the sufferer. It is occasionally relieved by flexing the thighs up against the chest. The pain is not relieved by inducing a bowel action with suppositories. The frequency of episodes varies from a few times weekly to once every few months. It is thought to be due to spasm in the levator ani muscles.

Treatment
There is no effective treatment. The hip flexion manoeuvre should be attempted. Galvanic electrostimulation of the puborectalis muscle has been reported to be successful but this technique is not widely available. Inhalation of a B2-agonist (salbutamol) may be of value. Patients should be reassured that there is no serious pathology in the rectum.

Descending perineum "syndrome"
Abnormal descent of the pelvic floor as a clinical sign was first recognised in 1970, and a clinical syndrome consisting of pelvic discomfort or pain, abnormal perineal (pelvic floor) descent, marked difficulty with defecation (obstructed defecation), and straining at stool was subsequently described. The pain is felt as a dull ache in the anal area and perineum, sometimes worse after defecation.

There is a variety of clinical conditions in which perineal descent and straining at stool are found including haemorrhoids, neurogenic faecal incontinence, urinary stress incontinence, solitary rectal ulcer syndrome, utero-vaginal prolapse, and rectocele. This group of conditions arises as a result of a functional obstruction to rectal evacuation which causes excessive straining during defecation.

The importance of this concept is that treatment of any of these conditions, eg haemorrhoidectomy, often will not cure the anal pain, which is caused by pelvic muscle weakness rather than by the associated condition. It is therefore important to decide in each case whether the pain is due to the muscle weakness or to the associated condition such as the haemorrhoids. Treatment should be directed at changing defecation habits and avoiding straining at stool.

Idiopathic perianal and perineal pain
Sometimes called perineal neuralgia, this is a condition of unknown aetiology affecting women in 80% of cases. The pain is characteristic and usually easily diagnosed on history; it is described as constant and unremitting, often with a feeling in the perineum like "sitting on a ball". In 75% of cases, the pain has been found to radiate into various places from its position of maximal intensity in the anal area, including the sacrum, pelvis and back of the thighs. In 50% of cases the pain is exacerbated when sitting. It is not worse during defecation. Patients have often undergone a variety of unsuccessful operations in the anal area including excision of skin tags, anal dilatation or treatment of haemorrhoids.

The cause of the pain is unknown. Clinical examination of the anal area and pelvic floor muscles, the pelvic gynaecological organs, and neurological examination provide normal findings. Investigations including X-ray examination of the spine and sacrum, and endoscopic examination of the rectum and sigmoid are all unhelpful. A neuralgia affecting the sacral or pudendal nerves has been postulated. Pelvic nerve ischaemia has also been considered. Although the absence of any weakness of the pelvic floor muscles is against the neuralgia hypothesis, it is possible that the injury is not sufficiently severe to lead to muscle weakness.

Management
It is very important to exclude other causes of chronic pain including chronic intersphincteric or supralevator abscess, endometriosis of the pelvis or rectovaginal septum, and pelvic or spinal lesions compressing the sacral plexus. A CT scan of the pelvis and CT myelography of the lumbosacral area should be carried out. To ensure that none of the above is overlooked, the diagnosis should be confirmed by a specialist. Treatment is very unsatisfactory. Standard analgesics or tricyclic antidepressants are usually not effective. Anticonvulsant drugs have been tried, without success. Transcutaneous or spinal cord stimulation has had poor results. Psychological counselling is sometimes required to assist the patient to cope with the pain.

Further reading

Daniel GL, Longo WE, Vernava AM. Pruritus ani. Causes and concerns. Dis Colon Rectum 1994; 37: 670-4.

Eckardt UF, Dodt 0, Kanzler G, Bernhard G. Treatment of proctalgia fugax with salbutamol inhalation. Am J Gastroenterol 1996; 91: 686-9.

Hancock BD. ABC of colorectal diseases. Anal fissures and fistulas. BMJ 1992; 304: 904-7.

Hancock BD. ABC of colorectal diseases. Haemorrhoids. BMJ 1992; 304: 1042-4.

Jones DJ. ABC of colorectal diseases. Pruritus ani. BMJ 1992; 305: 575-7.

Keighley MRB. Anorectal abscess. In: Keighley MRB, Williams NS (eds), Surgery of the anus, rectum and colon. London: WB Saunders, 1993: 397-417.

Loder PB, Kamm MA, Nicholls RJ, Phillips RK. Haemorrhoids: pathology, pathophysiology and aetiology. Brit J Surg 1994; 81: 946-54.

Mazier WP. Hemorrhoids, fissures, and pruritus ani. Surg Clin Nth Am 1994; 74: 1277-92.

Motson RW, Keck JO. Pathogenesis and treatment of anal fissure. In: Henry MM, Swash M (eds), Coloproctology and the pelvic floor. Oxford: Butterworths-Heinemann, 1992:394-402.

Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. Brit J Surg 1976; 63: 1-12.

Thomson WHF. The nature of haemorrhoids. Brit J Surg 1975; 62: 542-52.