Pruritus Ani
Pruritus ani is a dermatologic condition characterized by intense itching of the perianal skin, often caused by local irritants, infections, dermatologic disorders, or systemic conditions.
Murtagh Diagnostic Strategy
| Category | Diagnosis | Key Discriminator | Cantonese Question / Finding | Probability |
|---|---|---|---|---|
| Probability Diagnosis | Idiopathic / hygiene-related pruritus ani | Excessive wiping, soap/wet-wipe use; no visible lesion on inspection | 「你平時點樣清潔肛門？用咩嚟抹？」 | ~35% |
| Haemorrhoids with mucus discharge | Mucus soiling + prolapsing mass + PR bleeding [2][3] | 「有冇嘢凸咗出嚟？抹嘅時候有冇黐黐哋？」 | ~20% | |
| Perianal fungal infection (candida/tinea) | Erythematous, well-demarcated rash with satellite lesions; DM risk | 「肛門附近有冇紅色嘅疹？你有冇糖尿？」 | ~15% | |
| Threadworm (Enterobius vermicularis) | Nocturnal itch, visible worms, children/family affected | 「夜晚特別痕？見唔見到有蟲？」 | ~10% | |
| Serious Not To Miss | Anal / colorectal carcinoma | Palpable mass, weight loss, change in bowel habit, PR bleeding [4][5] | 「有冇消瘦？大便習慣有冇轉變？」 | ~2% |
| Perianal Crohn's disease / IBD | Chronic diarrhoea, fistulae, skin tags, extra-intestinal manifestations | 「有冇長期肚瀉或者肚痛？」 | ~1% | |
| Anal intraepithelial neoplasia (AIN) / Bowen's disease | Persistent erythematous plaque, HPV/HIV risk [4] | 「有冇一撻紅色嘅皮膚一直唔好？」 | <1% | |
| Pitfalls | Contact / irritant dermatitis (wet wipes, creams) | Well-demarcated eczematous rash matching area of contact [8] | 「你有冇用過新嘅藥膏或者濕紙巾？」 | ~15% |
| Anal fissure | Tearing pain on defecation + small amount of fresh blood [3] | 「去大便嗰陣有冇撕裂咁痛？」 | ~5% | |
| STI: condylomata acuminata (HPV warts) | Visible warty papules, sexual history | 「有冇肛門附近生咗粒粒？」 | ~3% | |
| Perianal fistula | Intermittent purulent discharge, history of abscess [9] | 「有冇膿或者臭嘅分泌物流出嚟？」 | ~2% | |
| Masquerades | Drugs (topical steroids → tinea incognito; antibiotics → candida) | Recent antibiotic or prolonged steroid use [8] | 「最近有冇食抗生素或者搽類固醇藥膏？」 | ~10% |
| Diabetes mellitus → candidal pruritus | Polyuria, polydipsia, HbA1c ↑; satellite lesions [6] | 「你有冇口渴、多尿嘅情況？」 | ~5% | |
| Cholestatic liver disease / CKD (uraemic pruritus) | Jaundice, dark urine, uraemic symptoms [7] | 「有冇眼黃、皮膚黃、小便深色？」 | ~2% | |
| Iron-deficiency anaemia | Pallor, fatigue, koilonychia | 「有冇面色蒼白、攰？」 | ~1% | |
| Trying to Tell Me Something? | Anxiety / OCD about hygiene | Excessive washing, psychosocial stress | 「你會唔會成日擔心嗰度唔乾淨？壓力大唔大？」 | ~10% |
| Fear of cancer | Family history of CRC, health anxiety | 「你最擔心嘅係咩？會唔會擔心係嚴重嘅病？」 | ~10% | |
| Embarrassment about STI or sexual practice | Reluctant to discuss sexual history | 「有冇其他關於性方面嘅擔心想傾？」(gently, after rapport) | ~5% |
| Time | Task | Cantonese Key Phrases | Why It Scores Marks |
|---|---|---|---|
| 0:00–0:30 | Greeting, rapport, open question | 「你好，我係X醫生，今日想同你傾下你嘅情況。你今日嚟呢度，最主要想睇啲咩呢？」(Hello, I'm Dr X, what mainly brought you here today?) | Friendly opening + elicits RFC; scores interpersonal marks |
| 0:30–1:30 | HPI: symptom analysis | 「你肛門痕嘅情況係幾時開始？痕咗幾耐？白天定夜晚特別痕？有冇嘢令到佢好啲或者差啲？」(When did the itch start? Worse day/night? Aggravating/relieving factors?) | Core HPI content for Case Report Form |
| 1:30–2:30 | Targeted Hx: red flags + associated Sx | 「有冇流血、痛、分泌物？大便習慣有冇轉變？有冇消瘦？」(Any bleeding, pain, discharge? Change in bowel habits? Weight loss?) | Screens for CRC, fissure, fistula, STI |
| 2:30–3:30 | PMH/Drug/Allergy/Family/Social/Sexual Hx | 「你以前有冇糖尿、皮膚病、腸炎？食緊咩藥？有冇抗生素過敏？屋企人有冇腸病？你做咩工作？有冇性接觸嘅情況想講？」 | Covers masquerades (DM, drugs) + psychosocial |
| 3:30–4:30 | ICE + hidden agenda | 「你自己覺得呢個痕係咩原因？你最擔心嘅係咩？今日你最希望我幫到你啲咩？」(What do you think is causing it? What worries you most? What do you hope I can do?) | Directly maps to ICE boxes on CRF |
| 4:30–5:15 | Empathy + signpost PE | 「我明白呢個痕真係好影響你瞓覺同生活，我哋可以幫到你。我想幫你檢查下肛門附近，你方唔方便？」 | Empathy statement + permission for examination |
| 5:15–6:00 | Summary, safety net, close | 「咁總結返，你主要係肛門痕咗X個星期，影響到瞓覺。我嘅初步睇法係…如果情況惡化或者有出血、消瘦，記得要返嚟跟進。有冇其他想問？」 | Summarising + safety net + checking understanding |
Uncovering the hidden agenda: Pruritus ani patients often have a hidden fear (e.g. cancer, STI, worms). Always ask 「你最擔心嘅係咩？」 early. The RFC may be the itch itself, but it may be fear of cancer, embarrassment about hygiene, or relationship strain from an STI concern.
| Domain | English Question | Cantonese Question | Why It Matters | If Positive, Think Of |
|---|---|---|---|---|
| Onset/Duration | When did the itch start? Constant or intermittent? | 「幾時開始痕？係成日痕定有時痕有時唔痕？」 | Acute vs chronic helps narrow DDx | Acute → contact/irritant; Chronic → haemorrhoids, dermatitis, fungal |
| Timing | Worse at night? | 「夜晚會唔會特別痕？」 | Nocturnal itch classic for pinworm (threadworm) & scabies [1] | Threadworm, scabies |
| Severity/Impact | Does it affect your sleep or work? | 「有冇影響到你瞓覺或者做嘢？」 | Functional impact → psychosocial problem for CRF | Psychological distress, sleep deprivation |
| Aggravating | Worse after defecation? After spicy food? After sweating? | 「去完廁所之後會唔會痕啲？食辣嘢或者出汗之後呢？」 | Post-defecation → haemorrhoids, fissure, poor hygiene; Moisture → fungal | Haemorrhoids, tinea cruris |
| Relieving | What have you tried? Creams? Scratching? | 「你有冇試過搽藥膏或者其他方法？」 | OTC steroid abuse can worsen tinea; prior Rx guides Mx | Tinea incognito, contact dermatitis |
| Associated: bleeding | Any blood on wiping or in stool? | 「抹嘅時候或者大便有冇血？」 | Red flag for CRC, haemorrhoids, fissure [2] | CRC, haemorrhoids, anal fissure |
| Associated: pain | Any pain during or after opening bowels? | 「去大便嗰陣有冇痛？」 | Tearing pain → fissure; throbbing → abscess/fistula [3] | Anal fissure, perianal abscess |
| Associated: discharge | Any mucus, pus, or fluid from the back passage? | 「有冇分泌物、膿或者黏液流出嚟？」 | Mucous → haemorrhoids/fistula; pus → abscess/fistula | Fistula-in-ano, haemorrhoids |
| Associated: lumps | Any lumps or swelling around the back passage? | 「肛門附近有冇粒嘢或者腫咗？」 | Prolapsing mass → haemorrhoids; hard lump → carcinoma [4] | Haemorrhoids, anal carcinoma |
| Bowel habits | Any change in bowel habits? Constipation? Diarrhoea? | 「大便習慣有冇轉變？有冇便秘或者肚瀉？」 | Red flag: alternating habit change → CRC [5] | CRC, IBD |
| Constitutional | Any weight loss, loss of appetite, fatigue? | 「有冇消瘦、冇胃口、成日攰？」 | Constitutional Sx → malignancy | CRC, anal carcinoma, lymphoma |
| Worms | Have you seen any tiny white threads in your stool or on underwear? | 「有冇見到大便或者底褲有啲白色好幼嘅蟲？」 | Pinworm (Enterobius) very common cause, especially in children/families [1] | Threadworm |
| Skin elsewhere | Any skin rash on other parts of the body? | 「身體其他地方有冇出疹或者痕？」 | Generalized → psoriasis, eczema, scabies, systemic cause | Psoriasis (inverse), eczema, scabies |
| Hygiene habits | How do you clean after opening bowels? Do you use wet wipes or soap? | 「你去完廁所之後點樣清潔？有冇用濕紙巾或者番梘？」 | Excessive cleaning / irritant products are a very common cause | Irritant contact dermatitis |
| PMH: DM | Do you have diabetes? | 「你有冇糖尿病？」 | DM → candidal infection, pruritus [6] | Perianal candidiasis |
| PMH: liver/renal | Any liver or kidney disease? | 「有冇肝病或者腎病？」 | Cholestasis → pruritus; uraemia → pruritus [7] | PBC, CKD |
| Drug Hx | Are you taking any medications? Antibiotics recently? | 「你食緊咩藥？最近有冇食過抗生素？」 | Antibiotics → candidiasis; topical steroids → tinea incognito | Candidiasis, drug-related |
| Sexual Hx | Any anal sexual contact? Any genital symptoms? | 「有冇肛交嘅性接觸？有冇其他生殖器官嘅症狀？」 | STI: HPV condylomata, herpes, gonorrhoea [4] | Condylomata acuminata, anal herpes, anal carcinoma |
| Family/Contacts | Anyone at home with similar itching? | 「屋企人有冇類似痕嘅情況？」 | Household contacts → scabies, threadworm | Scabies, pinworm |
| Occupation | What is your job? Any prolonged sitting? | 「你做咩工作？要唔要坐好耐？」 | Prolonged sitting/sweating → moisture, haemorrhoids | Haemorrhoids, intertrigo |
Case Report Form Answer Builder
- CC: Perianal itching (pruritus ani) for [X weeks/months]
- HPI points to capture: duration; constant vs intermittent; timing (nocturnal?); severity (sleep disruption?); aggravating factors (defecation, sweating, food); relieving factors (creams tried); associated symptoms (bleeding, pain, discharge, lumps, worms); bowel habit changes; constitutional symptoms; perianal hygiene practices; any visible rash/lesion
- Examples: "Persistent perianal itch affecting sleep," "Worried itch may be a sign of cancer," "Itch not responding to OTC treatment"
- Phrasing tip: The RFC is the patient's main concern today, which may differ from the symptom. Listen for the hidden worry.
| Component | Likely Examples |
|---|---|
| Ideas | "I think it might be haemorrhoids / worms / a fungal infection / cancer" |
| Concerns | "I'm worried it could be cancer," "I'm embarrassed," "It's affecting my relationship / sleep" |
| Expectations | "I want a cream to stop the itch," "I want to be checked for cancer," "I want a referral to a specialist" |
- In a typical FM exam scenario: Idiopathic (hygiene-related) pruritus ani or Haemorrhoids with secondary pruritus are the most common exam diagnoses.
- If DM cues given → Perianal candidiasis secondary to DM
- If worm cues given → Enterobius vermicularis (threadworm)
- Minimum supporting evidence: History of excessive perianal cleaning + no visible pathology on inspection (idiopathic); OR visible prolapsing pile + mucous discharge (haemorrhoids); OR satellite lesions + DM history (candidiasis)
| DDx | One Key Discriminator |
|---|---|
| Perianal fungal infection (candida / tinea cruris) | Well-demarcated erythema with satellite lesions; DM / recent antibiotics |
| Threadworm (Enterobius) | Nocturnal itch, visible worms, family members affected |
| Anal fissure | Tearing pain on defecation with small-volume fresh bleeding |
(Swap in anal carcinoma / STI / contact dermatitis depending on stem cues)
| Domain | Problem |
|---|---|
| Biological | Perianal skin irritation/excoriation from itch–scratch cycle; possible underlying haemorrhoids or infection |
| Psychological | Sleep disturbance and distress; embarrassment; anxiety about cancer or STI |
| Social/Functional | Difficulty concentrating at work; impact on intimate relationship; avoidance of social activities |
| Diagnosis / DDx | Best Supporting Physical Sign | How to Elicit | Why It Supports This Diagnosis |
|---|---|---|---|
| Idiopathic pruritus ani | Perianal excoriation / lichenification with no visible primary lesion | Visual inspection of perianal skin in left lateral position | Chronic scratching without primary pathology = idiopathic |
| Haemorrhoids | Prolapsing vascular cushion on straining / proctoscopy | Ask patient to strain; inspect perianal area; DRE and proctoscopy [2] | Visible prolapsed pile with mucous = cause of itch |
| Perianal candidiasis | Erythematous patch with satellite papules/pustules | Inspect perianal and inguinal skin | Satellite lesions are pathognomonic for candida |
| Threadworm | Visible adult worm on perianal inspection (esp. at night) or positive sellotape (Scotch tape) test | Apply adhesive tape to perianal skin in morning, examine under microscope | Directly identifies Enterobius ova/worms |
| Anal fissure | Visible mucosal tear at posterior midline on gentle parting of buttocks [3] | Gently part buttocks; do NOT perform DRE if acute fissure (too painful) | Posterior midline tear is classic; sentinel skin tag if chronic |
| Anal carcinoma | Palpable hard irregular mass on DRE + inguinal lymphadenopathy [4] | DRE + palpate inguinal LN | Hard mass + LN = high suspicion for malignancy |
| Contact dermatitis | Well-demarcated eczematous rash limited to area of contact [8] | Inspect; ask about contactants | Distribution matching product application area |
Top Traps That Lose Marks
- Not asking about hygiene practices – the #1 cause of pruritus ani in primary care is excessive cleaning / irritant use. If you don't ask, you miss the most likely diagnosis.
- Forgetting threadworm – extremely common in FM; ask about nocturnal itch and household contacts.
- Not screening for DM – perianal candidiasis may be the first presentation of diabetes. Ask about polyuria/polydipsia [6].
- Missing the cancer red flags – weight loss, change in bowel habit, PR bleeding in a patient > 50. Must document you asked.
- Not asking sexual history – STIs (condylomata, herpes, gonorrhoea) are easily missed; ask sensitively after rapport.
- Jumping to a biological diagnosis without ICE – the CRF specifically asks for ICE. The patient may have come because of cancer fear, not itch severity.
- Performing DRE on an acute fissure – this is painful and loses interpersonal marks. Say you would defer if patient in pain.
Must-Not-Miss Red Flags → Urgent Referral
- PR bleeding + weight loss + change in bowel habit → colonoscopy / urgent surgical referral
- Palpable hard anal mass → urgent surgical referral for biopsy [4]
- Non-healing perianal ulcer / plaque → biopsy to exclude AIN / Bowen's / carcinoma
- Atypical fissure (off-midline, multiple, non-healing) → exclude Crohn's, carcinoma, STI [3]
Shortest safe management / safety-net line (for consultation close):
「暫時嚟講，建議你用清水清潔，唔好用番梘或者濕紙巾，保持乾爽。我會安排驗血（包括血糖）同埋再檢查。如果情況差咗、有出血或者消瘦，一定要即刻返嚟。」 (Use plain water, avoid soap/wet wipes, keep dry. I'll arrange blood tests including glucose and follow-up. Return immediately if worsening, bleeding, or weight loss.)
High Yield Summary
What to ASK: Hygiene practices, nocturnal itch (worms), bleeding/pain/discharge/lumps, bowel habit change, DM symptoms, sexual history, drugs (antibiotics/topical steroids), household contacts, ICE.
What to WRITE on the CRF: Chief complaint with duration and functional impact; RFC (often cancer fear or treatment request); ICE verbatim; most likely Dx = idiopathic/hygiene-related pruritus ani OR haemorrhoid-related (match to stem); DDx = candidiasis, threadworm, anal fissure; biopsychosocial = excoriation (bio), sleep disturbance/embarrassment (psych), work/relationship impact (social); physical sign = perianal excoriation without primary lesion (idiopathic) or satellite lesions (candida).
What NOT to MISS: Cancer red flags (weight loss, bowel habit change, mass), DM as masquerade, threadworm in families, STI in at-risk patients, and always ask ICE.
Active Recall - Family Medicine Clinical Test
[1] Senior notes: Maksim Medicine Notes (p.72) – Scabies: clinical features, common sites, household contacts [2] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai) (p.748) – Haemorrhoids: clinical features, proctoscopy, referral indications [3] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai) (p.754) – Anal fissure: painful defecation, posterior midline, sentinel pile [4] Senior notes: Maksim Surgery Notes (p.116) – Anal carcinoma: HPV, palpable mass, inguinal LN, pruritus [5] Senior notes: Ryan Ho Fundamentals (p.283) – PR bleeding history taking: bowel habit change, red flags for CRC [6] Senior notes: Ryan Ho Endocrine (p.76) – Pruritus vulvae/perianal candidiasis as presentation of DM [7] Senior notes: Maksim Medicine Notes (p.219) – Uraemia: pruritus as clinical feature of CKD [8] Senior notes: Block A - Dermatology PBL 1 (p.11) – Contact dermatitis: well-demarcated, patch testing [9] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai) (p.760) – Anorectal fistula: purulent discharge, pruritus
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