The basics - Pruritus ani

Breaking the itch-scratch cycle is key to management.

ECzema: pruritus ani is rarely due to serious pathology
ECzema: pruritus ani is rarely due to serious pathology

Pruritus ani is defined as an uncontrollable desire to scratch the anus. It is a symptom and not an actual diagnosis.

This means that it is very important that appropriate investigations are performed to exclude an important underlying disease in patients who present with this symptom.

Pruritus ani is very common; it affects around one in 20 adults at some stage of their lifetime. It is around four times more common in men and most often affects people aged 40-70 years.

Most patients find it is worse at night, in warm weather and also after a bowel motion. Exacerbating factors may include wool, heat, moisture, faecal leaking and stress.

It can become a self-perpetuating problem resulting in an 'itch-scratch' cycle that can be difficult to break and can cause chronic skin changes.

Clinical presentation
It is very common for patients to delay seeking advice about this embarrassing condition, so they will often have a long history on presentation.

Any symptoms to suggest an underlying condition, for example altered bowel habit or blood in the motions need to be explored in the consultation.

Patients complain of usually very intense itching and burning around the rectum. There can also be associated anal pain and soreness.1

Examination may reveal excoriation of the perianal area or even lichenification in patients with a long history of the condition. A rectal examination of patients is mandatory.

Complications may include bleeding and formation of anal fissures. Patients with severe, persistent symptoms may become depressed.

Causes
The majority of cases of pruritus are idiopathic with an underlying pathology found in 10 per cent of cases.

An irritant in the stool (excess alkalinity, drugs e.g. antibiotics, tomatoes, wine, ale and caffeine) or intermittent stool seepage can lead to irritation on the skin and mucosa.

Colorectal and anal cancers may present with pruritus ani.

In children, the cause is mainly an infection with threadworms. However, faecal soiling, poor hygiene, local irritation and dietary agents may also be contributing factors.2

Management
Any underlying condition needs to be treated appropriately. Elimination of any irritants needs to be implemented.

Management includes introducing measures to reduce scratching, advising ways to gain general control and also instigate any necessary active treatment measures.3 Meticulous hygiene is extremely important.

Many patients find it very difficult to stop the 'itch-scratch' cycle. An injection of methylene blue may be used to control itching if other measures fail.

One recent study showed that an intradermal injection of methylene blue is effective and generally well tolerated for patients with refractory pruritus ani.4

Many patients find some relief with soothing ointments and creams (bismuth subgallate or zinc oxide).

Treatment with 1% hydrocortisone ointment may be beneficial for some patients. However, this should not be used long term because of contact dermatitis and skin atrophy.

More potent topical steroids should only be prescribed by specialists. Topical capsaicin has also been shown to reduce symptoms of severe intractable idiopathic pruritus ani.5

Although most patients respond well to simple measures, many have periodic relapses in the future.

Referral to a colorectal surgeon or dermatologist should be considered in any patient who has had no relief after three to four weeks of conservative measures.

General advice

  • Try to avoid scratching.
  • The perianal area should be washed with water after defecation.
  • Excessive wiping of the perianal area with toilet paper should be discouraged.
  • The skin should be patted dry (not wiped) with a soft towel or even by using a cool hairdryer.
  • Any soaps, perfumes or wipes should be avoided.
  • Loose-fitting cotton underwear should be worn.
  • Antihistamines may be beneficial (especially sedating ones at night time).
Causes of Pruritus ani
  • Dermatological conditions e.g. atopic dermatitis, lichen planus, lichen sclerosis, psoriasis.
  • Systemic disease e.g. diabetes mellitus.
  • Malignancy colorectal cancer, anal cancer, leukaemia, lymphoma.
  • Medications immunosuppressives, antibiotics.
  • Infections candidia, folliculitis, erythrasma (Corynebacterium minutissimum).
  • STIs e.g. syphilis, gonorrhoea, herpes simplex virus and HPV.
  • Threadworms more common in children (and their parents).
  • Anorectal disease e.g. haemorrhoids, fissures, rectal prolapse.

References

1. Kuehn HG, Gebbensleben O, Hilger Y, Rohde H. Relationship between anal symptoms and anal findings. Int J Med Sci 2009; 6: 77-84.

2. Stermer E, Sukhotnic I, Shaoul R. Pruritus ani: an approach to an itching condition. J Pediatr Gastroenterol Nutr 2009; 48(5): 513-6.

3. Siddiqi S, Vijay V, Ward M et al. Pruritus ani. Ann R Coll Surg Engl 2008; 90(6): 457-63.

4. Sutherland AD, Faragher IG, Frizelle FA. Intradermal injection of methylene blue for the treatment of refractory pruritus ani. Colorectal Dis 2009; 11(3): 282-7.

5. Lysy J, Sistiery-Ittah M, Israelit Y et al. Topical capsaicin - a novel and effective treatment for idiopathic intractable pruritus ani: a randomised, placebo controlled, crossover study. Gut 2003; 52(9): 1323-6.

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