Pruritis ani
This is intractable itching around the anus.
Usually the skin is reddened hyperkeratotic and may become cracked and moist.
The causes are numerous. A useful mnemonic is: ‘pus, polypus, parasites,
piles, psyche’.
•
Lack of cleanliness, excessive sweating, and wearing rough or woollen
underclothing are common causes.
•
An anal or perianal discharge which renders the anus moist. The causative
lesions include an anal fissure, fistula in ano, prolapsed internal or external
haemorrhoids, genital warts and excessive ingestion of liquid paraffin. A
mucous discharge is an intense pruritic agent and a polyp can be the cause.
•
A vaginal discharge, especially due to the Trichomonas
vaginalis.
•
Parasitic causes. Threadworms should be excluded, especially in young
subjects. Children suffering from threadworms should wear gloves at night, less
they scratch the perianal region and are reinfested with ova by nail biting —
‘parasites lost, parasites regained’. Scabies and pediculosis pubis may
infest the anal region.
• Epidermophytosis
is a common cause especially if the skin between the
toes is also infected. Microscopic and cultural examinations are
•
Allergy is sometimes the cause, in which case there is likely to be a
history of other allergic manifestations, such as urticaria, asthma or hay
fever. Antibiotic therapy may be the precipitating factor.
•
Skin diseases localised to the perianal skin — psoriasis, lichen planus
and contact dermatitis.
•
Bacterial infection. Intertrigo due to a mixed bacterial infection.
Erythrasma due to Corynebacterium
minutissimum is responsible for some cases and its presence is detected by
ultraviolet light which induces a pink fluorescence.
•
A psychoneurosis. It is alleged that in a few instances neurotic individuals
become so immersed in their complaint that a pain—pleasure complex develops,
the pleasure being the scratching. Possibly this is true, but such a syndrome
should not be assumed without firm grounds for coming to this conclusion.
•
Diabetes. Diabetes can sometimes present with pruritus ani and the urine
should be tested in all patients.
Treatment.
The cause is treated. Other methods include the following.
• Hygienic measures. Cotton wool should be substituted for toilet paper.
Soap is avoided and replaced by a detergent. These measures alone, combined with
wearing cotton cellular underwear and applications of calamine lotion, are all
that is necessary to cure some cases. If there is much anal hair trapping the
moisture and discharge, shaving can be very helpful.
• Hydrocortisone.
In cases
with dermatitis, and only in cases with dermatitis, prednisolone, applied
topically in a cream of 1 per cent is often beneficial; sometimes after
discontinuation of the therapy, the pruritus is liable to return, in which event
5 per cent xylocaine ointment can be substituted for a time.
•
Strapping the buttocks apart is a most useful procedure, especially when
the pruritus is acute, and in chronic cases when the opposing surfaces are
moist. The strapping is worn so long as the patient finds it beneficial.
Operative
treatment
This may be necessary for a concomitant lesion
of the anorectum which is thought to initiate or contribute to the pruritis.
Otherwise, surgery is not indicated.