ano-rectal pain

Aetiology of ano-rectal pain

thrombosed external haemorrhoid
anal fissure
perianal abscess
perirectal abscess
- ischio-rectal abscess
  - deep abscess within fat of ischiorectal fossa
  - can track to opposite side to form a horseshoe-shaped track
- submucous abscess following injection of haemorrhoids
- pelvi-rectal abscess
  - located above levator ani
  - usually follows pelvic cellulitis but may occur as complication of inflammatory bowel disease (IBD), diverticulitis, rectal Ca
external boil
pilonidal abscess
- occur in upper natal cleft
proctitis
prostatitis
traumatic injury / anal foreign body / sexual misadventure
proctalgia fugax
- recurring paroxysms of sudden, intense rectal pain usually lasting seconds to minutes
- usually at night
levator ani syndrome (LAS)
- a functional disorder causing chronic or recurrent rectal pain, often described as a dull ache or “sitting on a ball” sensation lasting >20 minutes.
- often worsen when sitting and improve with walking
- due to spasm of the pelvic floor muscles
coccydynia
- pain and tenderness of the coccyx
anal Herpes simplex virus (HSV)
perianal streptococcal dermatitis
- mainly in children - a bright red, sharply demarcated rash that is caused by group A beta-hemolytic streptococci

Other local conditions which usually do not have much pain

bleeding or prolapsed internal haemorrhoids
pilonidal sinus
- occur in upper natal cleft
anal fistula / fistula-in-ano
sentinel pile
- residual skin tag following anal fissure which can create hygiene issues and pruritus ani
pruritus ani
- mainly due to dermatoses (see below)
- in children, commonly due to pinworms which cause itch at night
- scabies
anal warts / condylomata acuminata
other anal skin pathologies
- skin cancer
  - perianal SCC
    - anal intraepithelial neoplasia (AIN)
      - assoc with HPV 16 and 18, often seen in HIV/AIDS
  - melanoma
  - etc
- perianal dermatoses:
  - perianal irritant contact dermatitis
    - excessive sweat or moisture
      - inadequate drying after bidet use
    - soaps and cleansers
    - faecal soiling
      - poor hygiene / sentinel pile / anal skin tags
      - overflow incontinence
      - frequent diarrhoea
      - prolonged soiling contact associated with incontinence pads
    - faecal irritants
      - eating spicy foods or taking laxatives such as co-danthrusate
  - allergic contact dermatitis
    - topical creams especially local anaesthetics
    - fragrances eg. in wet wipes, body washes
    - incontinence pads with colophony, acrylates or fragrances
    - rubber (eg. condoms)
    - nail varnish
  - atopic dermatitis
  - seborrhoeic dermatitis
  - lichen simplex
    - from excessive scratching
  - lichen sclerosis
    - usually women, often with associated vulval involvement
    - increased risk of perianal SCC
  - lichen planus
  - flexural psoriasis
  - intertrigo
    - an inflammatory rash in a skin fold, often due to sweat and friction
  - hidradenitis suppurativa
  - pemphigus vulgaris
  - benign familial pemphigus (Hailey-Hailey disease) typically involves skin folds including the skin around the anus.
  - extramammary Paget disease
- other skin infections
  - erythrasma
    - due to Corynebacterium minutissimum causes painless brown patch with characteristic coral red fluorescence is seen with a Wood lamp
  - candidiasis
    - usually has satellite lesions
  - tinea cruris