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Pruritus Ani

BASICS

  • Description: Intense anal/perianal itching and/or burning. Often acute (<6 weeks), but may become chronic.
  • Classified: Primary (idiopathic) or secondary (25–75%) to identifiable anorectal or systemic pathology.

EPIDEMIOLOGY

  • Incidence: 1–5% of general population
  • Predominant age: 30–50 years (all ages possible)
  • Sex: Male > female (4:1)
  • Prevalence: Underestimated due to underreporting

ETIOLOGY & PATHOPHYSIOLOGY

  • Most cases idiopathic (25–90%)
    • Often due to local trauma from wiping, scratching, or fecal contamination
  • Secondary causes: (inflammatory, infectious, neoplastic, anorectal, systemic, mechanical, psychogenic, dietary)
    • Dermatologic: allergic/atopic dermatitis, lichen simplex, psoriasis, lichen planus, seborrheic dermatitis, hidradenitis, radiation dermatitis
    • Anorectal: hemorrhoids, fissures, fistulas, proctitis, polyps, prolapse, diarrhea, constipation
    • Infectious: pinworms, bacteria (Staph, Strep, Corynebacterium), fungi (Candida), STIs (HSV, HPV), parasites, scabies, lice
    • Neoplastic: melanoma, SCC, BCC, colorectal, Paget, Bowen disease
    • Systemic: diabetes, cholestasis, renal/liver failure, HIV, anemia, hyperthyroidism, lumbosacral radiculopathy
    • Mechanical: vigorous cleaning, synthetic/tight clothes
    • Chemical irritants: soaps, wipes, perfumes, antibiotics, topical anesthetics
    • Dietary: citrus, chocolate, coffee/tea/cola, dairy, tomatoes, nuts, alcohol
    • Psychogenic: anxiety, compulsive scratching
  • Risk factors: obesity, excessive hair, moisture, atopy, anorectal pathology, anxiety, caffeine

PREVENTION

  • Gentle perianal hygiene; avoid harsh soaps and vigorous wiping
  • Minimize moisture (absorbent cotton, powders)
  • Avoid triggers (caffeine, dietary irritants, tight/synthetic clothes)
  • Regular, formed stools (avoid laxative abuse)

ASSOCIATED CONDITIONS

  • Psoriasis (5–55%)
  • Hemorrhoids (up to 52%)
  • Coexisting systemic or anorectal diseases

DIAGNOSIS

History

  • Anal/perianal itch, burning, excoriation
  • Hygiene practices, toiletry changes, bowel habits, bleeding, discharge, diet (esp. “C's”: caffeine, chocolate, citrus, dairy)
  • Medical/family history (psoriasis, eczema, DM, hepatitis, colorectal CA)
  • Household contacts/pets (parasites)
  • Anal intercourse

Physical Exam

  • Inspect perianal area: erythema, lichenification, fissures, warts, polyps, maceration, excoriations, evidence of stool seepage, suspicious lesions
    • Staging: 1—erythema; 2—lichenification; 3—coarse/ulcerated
  • DRE: sphincter tone, masses, pain
  • Anoscopy: hemorrhoids, fissures, internal lesions

Differential Diagnosis (ITCHeS acronym)

  • Infection: Candida, parasites, bacteria, HPV, HSV
  • Topical irritants: soaps, detergents, garments
  • Cutaneous/Cancer/Colorectal: eczema, psoriasis, lichen, skin cancer, anal/colorectal cancer, fissures, prolapse, hemorrhoids
  • Hypersensitivity: foods, drugs
  • eSystemic: diabetes, anemia, cholestasis, malignancy

Initial Tests

  • Pinworm tape test/stool O&P
  • CBC, CMP, A1c, thyroid panel
  • Wood lamp for erythrasma
  • KOH for fungi; mineral oil prep for scabies
  • Perianal skin culture (superinfection)
  • Hemoccult for occult bleeding
  • Anal STI PCR if risk factors

Follow-Up/Special Testing

  • Biopsy suspicious/refractory lesions (exclude neoplasia)
  • Colonoscopy if high suspicion for colorectal pathology (esp. age >40, FHx, bleeding, weight loss, altered stool)
  • Pediatric: pinworm, Crohn disease

TREATMENT

General Measures

  • Meticulous but gentle hygiene: water-moistened cotton swabs, avoid tissue paper, pat dry or use hair dryer (cool)
  • Avoid irritants: perfumed products, baby wipes, soaps, harsh rubbing
  • Loose, cotton clothing
  • Minimize moisture (cotton, talcum, cornstarch)
  • Add fiber for formed stools; address fecal incontinence
  • Cotton gloves at night to reduce scratching

Medication

First Line - Treat infection: topical imidazoles (fungal), antibacterials, albendazole (pinworm) - Treat anatomic: band hemorrhoids, treat fissures/fistulas - Break itch-scratch cycle: low-potency topical steroid (hydrocortisone 1% ointment up to QID, ≤2 weeks) - Sedating antihistamines at night (avoid in elderly) - Barrier creams: zinc oxide, petroleum jelly after steroid - Tricyclics, SSRIs, gabapentin for refractory/psychogenic pruritus

Second Line - High-potency steroid (short course if needed) - Topical capsaicin (low-dose) - Tacrolimus 0.03% ointment - Intradermal methylene blue (“anal tattooing”) in recalcitrant cases - Biologics (dupilumab) in severe refractory cases (limited data)

Diet

  • Eliminate: caffeine, coffee, cola, chocolate, citrus, dairy, tomatoes, nuts, alcohol, vitamin C supplements, spicy foods
  • Bulk stool with fiber to reduce leakage

Referral

  • Gastroenterology or dermatology if refractory
  • Colonoscopy if high risk or persistent symptoms

Procedures

  • Biopsy lesions, treat underlying malignancy or refractory cases surgically as indicated

ONGOING CARE

  • Follow up every 2 weeks if not improving
  • Monitor for lichenification, excoriation, secondary infection, or persistent symptoms (consider underlying neoplasia)

PATIENT EDUCATION

  • Gentle cleansing, avoid soaps and rubbing
  • No ointments/mineral oil unless prescribed
  • Wear loose, cotton clothing
  • Keep area dry
  • Avoid dietary triggers
  • Use plain water enema if incomplete rectal emptying/soiling

PROGNOSIS

  • Conservative therapy effective in ~90% of cases
  • Idiopathic pruritus ani often chronic and relapsing

COMPLICATIONS

  • Secondary infection, abscess
  • Lichenification, fissures, chronic excoriation
  • Significant reduction in quality of life

ICD-10 CODE

  • L29.0 Pruritus ani

CLINICAL PEARLS

  • Pruritus ani is a symptom, not a disease; consider underlying pathology
  • Conservative management (hygiene + trigger avoidance) resolves most cases
  • Dietary elimination of the “C’s” is a key trial (caffeine, chocolate, cola, citrus, dairy, vitamin C)
  • Rule out infection (esp. in immunocompromised), and always consider neoplasia if refractory