Pruritus ani

Section: Colorectal Sub-section: Proctology Curriculum: Nil

Colorectal Surgery A Companion to Specialist Surgical Practice 1, page 249

Definition

Perianal itch

Pathophysiology

Local pathology permitting stool to leak to the outside or to difficulty with thorough anal cleansing, or to anal sphincteric dysfunction or other contributory causes such as irritative foods and, importantly, a high-fibre diet.

Causes

Idiopathic

• Thought to be caused by local irritant such as bacterial endopeptidases and faecal allergens.
• Patients with idiopathic pruirits ani have lower threshold for internal anal sphincter relaxation and lower retention capacity so may have increased leakage.
• Faecal contamination is thought to contribute to idiopathic PA, as are certain medications – those that promote loose stool or release histamine, certain foods, and trauma – from wiping, obesity and moisture. Foods and beverages include coffee, colas, tea, chocolate, tomatoes and beer

Secondary

• Neoplasia • Rectal adenoma • Rectal adenocarcinoma • Anal squamous cell carcinoma • Malignant melanoma • Bowen’s disease • Extramammary Paget’s disease
• Benign anorectal conditions • Haemorrhoids • Fistula-in-ano • Anal fissure • Rectal prolapse • Anal sphincter injury or dysfunction • Faecal incontinence • Radiation proctitis • Ulcerative colitis
• Infections • Condyloma acuminatum • Herpes simplex virus • Candida albicans • Syphilis • Lymphogranuloma venereum • Enterobius or threadworm
• Dermatological • Neurogenic dermatitis • Contact dermatitis • Lichen simplex • Lichen planus • Lichen atrophicus

Clinical

Physical examination. Physical examination should include any evidence of skin disease. The perineum and underclothes should be carefully inspected for any reason for soilage. Digital rectal examination may reveal anal sphinc- teric dysfunction or other reasons for the pruritus. Wiping with a moist gauze may confirm staining and thus anal leakage.

Repeat examination after straining may be required to reveal a rectal prolapse. Endoscopy may be required in certain cases. Skin lesions may need to be biopsied and examined for fungus or other dermatological problems (this is very rare).

Clinical finding of Lichan traumaticus - thick leathery skin

Investigations

• Benign - Proctography, manometry, anal uss
• Infectious - swabs, scrapping
• Dermatological - biopsy, allergy testing
• Neoplastic - biopsy

Treatment

Dependent on the primary pathology

Aim:

• Reduction of leakage
• Maintenance of good personal hygiene
• Prevention of further injury to the perianal skin.

Soilage

• Decreased by reducing flatulence
• Decreased lowering dietary fibre and adding probiotics.

Loose stools

• Treated with antimotility medications

Hygiene:

• Cleansing of the perineum using water with drying by gentle dabbing

Treat Itch:

• An anti-itch powder
• antihistamine medication may be useful to break the vicious cycle of itching and scratching.
• Loose underwear
• Short-term use of a hydrocortisone cream may help to break the cycle

Refractory pruritis ani

• Topical capsaicin
• Topical Tacrolimus (poor evidence) but an option
• Tattooing with methylene blue destroys the nerve endings around the anus → nerves may grow back.

Treatment approach

1. Stop any anal creams
2. Clean with water only (stop using toilet paper)
3. Stop caffeine + FODMAP diet (if IBS-D)
4. Flare - assume it is related to seepage
   1. Immediately clean with water
   2. Dab dry
   3. Barrier cream
5. Pelvic floor issue - treat appropriately