Pruritus ani

Typical Patient Profile:

• Typically an anxious and/or overweight male aged 40–60 years.
• Often has a colonic reflex associated with stress.
• Experiences persistent pruritus and constant urge to scratch, causing distress and embarrassment.

Aetiology

Idiopathic Causes:

• Up to a quarter of cases of anal pruritus are idiopathic.

Benign Aetiology:

• Majority of cases result from a combination of faecal soiling and dietary factors.
• Local anorectal disorders and contact dermatitis of the perianal skin may exacerbate the problem.

Faecal Soiling, Diet, and the Itch-Scratch Cycle

Causes of Faecal Soiling:

• Poor hygiene, anatomical abnormalities (e.g., haemorrhoids, fissures, skin tags), or internal anal sphincter dysfunction.
• Abnormal bowel motions, including diarrhoea (food intolerance, antibiotics, laxatives, enemas) and constipation (causing fissures).

Contributing Factors:

• Sweating associated with inappropriate clothing or obesity.
• These factors lead to irritation and subsequent scratching, damaging the perianal skin and worsening the itch-scratch cycle.

Anorectal Conditions

Common Conditions:

• Up to half of patients with pruritus ani have an anorectal disorder, most commonly haemorrhoids.

Serious Conditions:

• Anal cancers, perianal Paget disease, and perianal Bowen disease may present with itch.

Skin Disorders

Contact Dermatitis:

• Caused by a wide range of topical agents (soaps, shower gels, creams, talc, perfumed/bleached toilet paper, baby wipes, latex condoms).
• Patients often overwash with soap products or use over-the-counter products, worsening the problem.

Therapeutic Agents:

• Haemorrhoid preparations can cause contact dermatitis (e.g., benzocaine, a common allergen).

Infections

Fungal Infections:

• Account for up to 15% of cases of pruritus ani.
• Candida is more likely pathogenic in patients with diabetes, after steroid treatment, and after systemic antibiotic use.

Bacterial Infections:

• Include beta haemolytic streptococci and Staphylococcus aureus, causing chronic symptoms.
• Erythrasma, a cutaneous infection by Corynebacterium minutissimum, can be diagnosed by Wood’s light fluorescence.

Parasitic Infections:

• Threadworms, often infect multiple family members.
• Sexually transmissible infections (STIs) including genital warts, genital herpes, syphilis, gonorrhoea, Chlamydia trachomatis, molluscum contagiosum, and scabies.

Investigations

Initial Review:

• Comprehensive history and full physical/dermatological examination are crucial.
• Consider factors like resource limitations, cognitive impairment, depression, or physical disability in the elderly that may lead to neglect of hygiene.

Tests:

• Full blood count (infection, worm infestation, atopy).
• Immunoglobulin E.
• Blood glucose.
• Syphilis serology (if signs of possible syphilis infection).
• Tissue transglutaminase (coeliac screen).
• Swabs for microscopy and culture (fungal, streptococcal, staphylococcal, gonococcal, and Corynebacterium infections).
• Anal PCR swabs for STIs, PCR swabs from lesions for HSV, syphilis, and vaginal swabs.
• Patch tests if contact dermatitis is suspected.
• Nocturnal cellotape test and/or stool test for helminths.

Management

Normalisation of Bowel Motions:

• Additional fibre and adequate fluid intake to achieve well-formed stools.

Cleaning After Defaecation:

• Avoid overzealous cleaning.
• Use non-irritant cleaning methods (bidet, lukewarm water, wet cloth, or moist cotton wool).

Clothing:

• Wear loose, natural fibre clothing.
• Avoid prolonged sitting.

Soaps and Cleansers:

• Advise against using soap; use aqueous cream or soap-free cleanser.
• Cease the use of other creams or potential irritants.

Avoid Scratching:

• Trim fingernails and wear gloves or mittens to bed to prevent scratching during sleep.

Medications:

• Zinc cream.
• Mild hydrocortisone 1% ointment (contains fewer potential preservative irritants).