Anorectal Pain
This is usually severe and distressing. Because of reflex sphincteric spasm, constipation very often follows and increases the pain and suffering further. Adequate examination is also difficult for the same reason; fortunately if a PR exam is too difficult, a visual inspection can often yield the diagnosis.
Differential diagnosis
Common Diagnoses
- Anal Fissure
- Thrombosed Haemorrhoids/Perianal Haematoma
- Perianal Abscess
- Proctalgia Fugax (PF)
- Anorectal Malignancy
Occasional Diagnoses
- Levator Ani Syndrome
- Crohn’s Disease
- Coccydynia
- Descending Perineum Syndrome
- Prostatitis
- Ovarian Cyst or Tumour
- Solitary Rectal Ulcer Syndrome
Rare Diagnoses
- Anal Tuberculosis
- Cauda Equina Lesion
- Endometriosis
- Trauma
- Presacral Tumours
Ready reckoner
Key distinguishing features of the most common diagnoses
| Anal Fissure | Haematoma | Abscess | PF | Malignancy | |
|---|---|---|---|---|---|
| Began While Defecating | Yes | No | No | Possible | No |
| Visible Anal Swelling | No | Yes | Possible | No | Possible |
| Pain Intermittent | Possible | No | No | Yes | No |
| Rectal Bleeding | Yes | Possible | Possible | No | Yes |
| PR Exam Excruciating | Yes | Yes | Yes | Possible | Possible |
Possible investigations
Likely: None
Possible: FBC, ESR/CRP, proctoscopy, faecal calprotectin
Small Print: Urinalysis, ultrasound, hospital-based lower GI investigations
- FBC/ESR/CRP: WCC may be raised in abscess and Crohn’s disease. ESR/CRP raised in these and carcinoma.
- Proctoscopy valuable if pain allows (specialist might also take biopsy).
- Faecal calprotectin: May help in diagnosing Crohn’s disease.
- Urinalysis: Pus cells and blood may be present in prostatitis or invasive bladder tumour
- Ultrasound of pelvis if pelvic examination reveals a mass. In obscure cases, hospital-based lower GI investigations may be needed.
Top Tips
- If the patient uses dramatic language (e.g. red-hot poker) to describe fleeting pain, is otherwise well and there are no obvious abnormalities on examination, the diagnosis is likely to be proctalgia fugax.
- Examine the patient – the cause is usually a thrombosed pile/perianal haematoma, anal fissure or an abscess, and these can usually be diagnosed by simple inspection
- Provide symptomatic relief but remember to deal with any underlying causes – especially constipation.
- Don’t forget to ask about thirst and urinary frequency – recurrent abscesses may be the first presentation of diabetes.
Red Flags
- Preceding weight loss and/or change in bowel habit should prompt a full urgent assessment with carcinoma and inflammatory bowel disease in mind.
- Some perianal abscesses do not result in external swelling. If PR exam is prohibitively painful, consider this possibility – especially if the patient is febrile
- In florid or recurrent perianal problems, think of Crohn’s disease as a possible cause.
- Remember rarer causes in intractable, constant pain in a patient with no obvious signs on PR.