Pruritus ani

Published on 18/03/2015 by admin

Filed under Dermatology

Last modified 18/03/2015

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Pruritus ani

Gabriele Weichert

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

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Pruritus ani represents a chronic, idiopathic intensely pruritic sensation of perianal skin. Long-standing cases are associated with significant discomfort, embarrassment, and sleep disturbance. Chronic primary pruritus ani shows lichenification and excoriations of the perianal area in the absence of primary skin disorders, infections, or neoplasms.

Management strategy

When evaluating a patient, any contributing primary skin disorders must be identified. These may include atopic dermatitis, psoriasis, or lichen sclerosis. Neoplasms, hemorrhoids and anal fissures, infectious etiologies such as genital warts, tinea, candidiasis, infestations such as pinworms and scabies, and bacterial infections (e.g., β-hemolytic streptococcus) must be ruled out by clinical examination and appropriate investigations. With this approach, most causes of acute pruritus ani can be identified and treated. It is the patient in whom none of the above factors are identified who suffers from chronic or idiopathic pruritus ani. History may reveal atopy or sensitive skin, leading to an increased itch sensation from all causes.

A history of the management, including cleansing habits, may reveal a sensitizer (such as a wet wipe) causing a contact dermatitis. Over-cleansing is not uncommon and may be irritating. Many of these patients suffer from low-grade fecal incontinence. This is often evident on examination of the underclothes or of the perianal skin. A history of over-zealous cleansing routines or sleep disturbance is common. Potential topical sensitizers should be stopped. A biopsy should be performed if the diagnosis is in doubt. Avoidance of toilet paper to cleanse the area after bowel movements can be helpful, as this may be abrasive.

Advise patients to cleanse the perianal skin twice a day and after bowel movements using cotton balls or cotton squares (make-up removal pads) moistened with warm water or a liquid cleanser. Patients with low-grade fecal incontinence should perform this routine several times a day. Cleansing has been shown to be as effective as topical steroids. A short (few weeks) course of a low- to mid-potency topical steroid is recommended. Caution must be taken with prolonged high-potency steroid use, as this area is prone to atrophy. Potency should be reduced as symptoms improve. Topical tacrolimus may be used in clearance or maintenance treatment. Topical zinc paste can limit the degree of irritant dermatitis in patients with fecal incontinence. An evening sedating antihistamine may provide welcome sleep in the early weeks of treatment.

If a patient fails to improve, lower gastrointestinal investigations should be considered to rule out neoplastic disease. Patch testing should be performed in patients who fail to improve. Avoidance of caffeine and increased dietary fiber may be helpful. For second-line therapy, topical capsaicin 0.006% three times a day for 4 weeks could be used. Capsaicin will cause perianal irritation in most patients during the therapy. Finally, intralesional steroid injections to the perianal skin may be considered. Intradermal methylene blue injections are reported to damage dermal nerve endings and provide relief. Injection with phenol in almond oil has been reported to be beneficial.