Anorectal Pain
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
- Solitary Rectal Ulcer Syndrome
- Ovarian Cancer
- Ovarian Cyst
Rare Diagnoses
- Anal Tuberculosis
- Cauda Equina Syndrome
- 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.