Anal pain

Chapter 21 ANAL PAIN




KEY POINTS



• The differential diagnosis of anal pain includes anal fissure, abscess and proctalgia fugax. Haemorrhoids rarely cause pain unless they are complicated by thrombosis.

• Patients with thrombosed external haemorrhoids (perianal haematoma) present with severe pain associated with a tense bluish lump adjacent to the anal verge.

• Patients with perianal haematoma present with severe pain and a tense bluish lump adjacent to the anal verge.

• Thrombosed internal haemorrhoids can occur when prolapse becomes irreducible. Conservative treatment involves bed rest, elevation, ice, analgesia and aperients.

• When an anal fissure is not situated in the posterior or anterior positions, a secondary aetiological factor such as Crohn’s disease, infection or malignancy should be considered.

• Proctalgia fugax is a benign fleeting pain in the perineum that often wakes patients.

• Pruritus ani results in distressing itching and excoriation around the anus.


CAUSES OF ANAL PAIN


There are many causes of anal pain (Table 21.1). Patients usually attribute anal pain to haemorrhoids. However, haemorrhoids rarely cause pain unless they are complicated by prolapse and thrombosis. There is usually some delay in presentation because of patient embarrassment. A thorough history and careful examination can usually elicit the diagnosis without need for further investigations (Figure 21.1). Occasionally, other investigations are required and may include examination under anaesthesia, biopsy and pathological analysis, sigmoidoscopy, endoanal ultrasound and magnetic resonance imaging (MRI).


TABLE 21.1 Causes of anal pain















Frequency Causes
Common
• Anal fissure

• Anorectal abscess/fistula

• Thrombosed external haemorrhoid

• Thrombosed internal haemorrhoid

• Proctalgia fugax

• Pruritus ani

• Postoperative (anal procedures)
Infrequent
• Rectal prolapse

• Foreign body

• Faecal impaction

• Hidradenitis suppurativa

• Crohn’s disease

• Low pilonidal abscess

• Bartholin’s abscess
Rare
• Anal tumours (squamous cell carcinoma, melanoma, Bowen’s disease, Paget’s disease, basal cell carcinoma)

• Rectal cancer

• Tumours of pelvic bones or organs (prostate, cervix, vulva, vagina or urethra)

• HIV and other sexually transmitted infections

• Tuberculosis and actinomycosis

image

FIGURE 21.1 Diagnosis of anal pain.



Anal fissure


Anal fissure is caused by a tear in the mucosa of the anal canal, usually from a hard stool. It causes anal pain worse on defecation, lasting for several hours and associated with a small amount of bright red rectal bleeding. Physical examination may reveal the triad of internal anal papilloma, anal fissure and external sentinel skin tag. Sphincter muscle is present in the base of the fissure. Of all anal fissures, 90% are located in the posterior region, 5% in the anterior region and 5% in other areas. When an anal fissure is not situated in the posterior or anterior positions, a secondary aetiological factor (e.g. Crohn’s disease, infection or malignancy) should be entertained. Delay in healing of anal fissures has been attributed to impaired blood supply, demonstrated on ultrasound Doppler studies and postmortem studies.


Conservative treatment with addition of aperients, increased fibre and fluid intake and warm baths after each bowel motion is effective. The addition of topical ointments can help relieve pain. Topical glyceryl trinitrate has been shown in some studies to promote healing by its effect on nitric oxide to enhance sphincter muscle relaxation. Botulinum toxin and other drugs (e.g. calcium antagonists) have been used with varying success.


Lateral internal anal sphincterotomy is the most effective surgical treatment for anal fissures. However there is a risk for future incontinence because some sphincter muscle is divided. It is unclear how much internal anal sphincter needs to be divided: some surgeons advocate division to the height of the fissure and others advocate minimal division. Posterior internal anal sphincterotomy and anal dilatation are rarely performed now because of the risk of keyhole deformity and uncontrolled sphincter tears, respectively. Other surgical options include fissurectomy (excising the edges of the fissure to stimulate healing) and advancement flaps to cover the defect.

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Mar 29, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Anal pain

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