Pruritus ani

Patient Information Leaflet
Link: Pruritus ani (itchy bottom)

https://www.pcds.org.uk/patient-info-leaflets/pruritus-ani-itchy-bottom

Pruritus ani is a common condition characterised by the sensation of perianal itching or burning. Most cases are idiopathic or hygiene-related, but it can be secondary to an underlying skin condition, or occasionally a bowel disorder.

This chapter is set out as follows:

• The true incidence of pruritus ani is unknown with figures varying from 5-20%. It appears to be more common in men than women. Pruritus ani most commonly affects people between the ages of 40-60 years, although any age group can be affected. There are many different causes / contributing factors - refer to the section on clinical findings 

In order to ascertain the diagnosis patients require:

• An accurate history including bowel habit and hygiene regime 
• Examination of the perianal skin (and the genitalia if lichen sclerosus is suspected) 
• A digital rectal examination in appropriate cases
• Skin swabs
• Additionally, some patients require a more thorough skin examination if the likely cause is an inflammatory skin condition

Once this assessment has been made the differential can be broadly divided in to four categories (there may be overlap):

• Hygiene-related
• Inflammatory skin conditions 
• Infection
• Lower GI pathology

Hygiene-related 

• Too little cleansing leaves irritating stool and sweat residue on the peri-anal skin. This problem can sometimes be exacerbated by certain foods or beverages such as spicy foods, citrus fruits, beer and caffeine - signs of faecal staining or soilage suggests inadequate hygiene
  
• Too much cleansing, often with sanitary wipes and strong soaps, can be drying or irritating or occasionally cause a contact allergic dermatitis

Inflammatory skin conditions 

• Significant perianal erythema may suggest an inflammatory dermatosis, or infection
  
• Several inflammatory dermatoses such as eczema and psoriasis can cause itch, erythema and sometimes lichenification. If psoriasis is suspected do a thorough skin examination including the scalp and nails 
• Lichen sclerosus should be suspected if the skin is ivory white
• Contact allergic dermatitis can occur secondary to a number of topical treatments, some of which may be used in the treatment of haemorrhoids. These treatments may have been prescribed or purchased over-the-counter 

Infection

• Threadworms are a common cause of pruritus ani in children, and occasionally adults. Itching is usually worse at night. Threadworms look like thin, white, cotton threads. They can sometimes be seen on the stools in the toilet. If the child / parent cannot see the threadworms, but suspects the child may have them they can try looking at the child's back passage in the late evening - if the child has threadworms one or two can often be seen coming out of the anus 
• Bacterial infection including streptococci
• Yeast infection especially candida albicans

Digital rectal examination

• Is there any change of bowel habit, bleeding, discharge, incontinence, palpable lump or abdominal pain that could suggest malignancy?
• Local gastrointestinal pathology such as haemorrhoids and anal skin tags can exacerbate matters - large external haemorrhoids or anal skin tags (some of which arise secondary to old external haemorrhoids) can make post-defecation cleansing difficult, and large internal haemorrhoids can cause mucous drainage or faecal soilage and consequent irritation. Sphincter tone can be assessed by having the patient contract the sphincter during digital rectal examination - the patient should then be asked to bear down as if for a bowel movement, which may show prolapsing internal haemorrhoids. Anoscopy may be necessary to further evaluate the anorectum for haemorrhoids
• Sinuses and/or fistulas can suggest inflammatory bowel disease 

• All patients require a swab for microscopy, culture and sensitivity (MC&S)

• Referral for gastrointestinal investigations will occasionally be required. If there are any red flags of malignancy then an urgent referral will be needed

General management 

• Refer to the top right of the page for a patient information leaflet available through a QR code or printable PDF 
• A good hygiene regime is important 
• Avoid or limit any dietary triggers
• Ideally patients should have a good bowel habit, and go once a day. Patients should also avoid straining as this can cause haemorrhoids or fissures. Such matters may need addressing by way of a high-fibre diet and/or a natural laxative such as ispaghula husk (Fybogel ®)
• An emollient cream used regularly, including after a bowel motion and before bed, is often helpful. Some patients also find applying Vaseline ® before a bowel motion of benefit as it has a barrier effect

Infection

• Treat relevant infections such as threadworms, streptococcus, and candida 

Inflammatory skin conditions and lichen sclerosus 

• Emollients - patients should use both a moisturising emollient cream and a soap-substitute (the same cream can be used for both). Patient preference is important 
• A mildly potent topical steroid such as Eumovate ® cream may need to be used periodically, and is safe to use in the long-term. For severe inflammatory changes the short-term use of a potent topical steroid may be required
• If symptoms are very significant and do not respond adequately to treatment consider referral for patch tests to look for contact allergic dermatitis

Lichen sclerosus 

• Refer to the chapter  Lichen sclerosus 

GI pathology

• If haemorrhoids or anal skin tags remain a problem the patient may need to be referred for further management 
  
• If bowel cancer is suspected refer urgently (two-week wait)