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Perianal Abscess

Clinical Subject Page

Perianal Abscess

A perianal abscess is a localized collection of pus near the anus caused by infection of
the anal glands. It is an anorectal emergency that usually requires prompt surgical
drainage

Also called

Anorectal Abscess

ICD-10

K59.31

Specialty

Gastroenterology

Onset

Chronic

Reviewed

July 2026

On This Page

Overview

Perianal abscess is the most common type of anorectal abscess and usually results from obstruction and infection of the anal glands (cryptoglandular infection). Patients present with severe anal pain, swelling, and fever. Delayed treatment may lead to fistula formation or sepsis

Etiology & Risk Factors

Etiology
Most perianal abscesses arise from infection of the anal glands located within the
intersphincteric space.


Risk Factors
– Cryptoglandular infection (most common)
– Crohn disease
– Diabetes mellitus
– Immunosuppression (e.g., HIV, chemotherapy)
– Obesity
– Smoking
– Previous anorectal abscess
– Previous anal fistula
– Local trauma
– Hidradenitis suppurativa

Pathophysiology

Obstruction of an anal gland within the intersphincteric space → bacterial overgrowth and infection (commonly mixed aerobic and anaerobic organisms) → pus formation → spread of infection through the perianal or perirectal spaces → abscess formation → increasing pressure causes pain and tissue inflammation → spontaneous drainage or surgical incision may occur → persistent infected tract may heal incompletely and develop into an anal fistula (fistula-in-ano) if the internal opening remains patent

Clinical Presentation

Common Symptoms
– Severe constant anal pain
– Pain worsens with sitting or defecation
– Perianal swelling
– Tender lump near the anus
– Fever
– Malaise
– Purulent discharge (if ruptured)


Deep Abscesses
– Severe rectal pain
– Fever and chills
– Pelvic discomfort
– Minimal external swelling

History Taking

Ask about: Onset and duration of pain, Fever or chills, Swelling around the anus,
Purulent discharge, Pain during defecation, Previous abscess or fistula, History of Crohn
disease, Diabetes, Immunosuppression, Recent anorectal trauma or surgery

Physical Examination

General Examination
– Temperature
– Signs of sepsis
– General appearance


Perianal Examination
Look for: Erythema, Swelling, Fluctuant tender mass, Warmth, Purulent drainage,
Cellulitis


Digital Rectal Examination
– May reveal deep tenderness
– Perform gently and only if tolerated

Investigations

Laboratory Tests
– CBC (leukocytosis)
– CRP and ESR
– Blood glucose (screen for diabetes)
– Blood cultures only if septic or immunocompromised


Imaging

Usually NOT Required
Typical superficial perianal abscesses do not require imaging before treatment.


Pelvic MRI (Best imaging test)
Indications: Suspected deep abscess, Complex or recurrent abscess, Suspected fistula,
Crohn disease, Uncertain diagnosis


CT Pelvis
Used when: MRI unavailable, Suspected pelvic extension, Severe sepsis, Emergency
evaluation


Endoanal Ultrasound
May identify fistula tracts in selected patients.
Important Note
Most superficial perianal abscesses are diagnosed clinically and treated immediately.

MRI is preferred when a deep or complex abscess is suspected

Diagnosis

Diagnosis is based on: Severe anal pain, Tender fluctuant perianal swelling, Physical
examination findings, MRI when deep or complex disease is suspected.

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Management

1. Incision & Drainage (Definitive Treatment)
– Perform as soon as possible
– Immediate drainage of pus
– Send pus for culture only in selected patients

2. Antibiotics
Not routinely required after drainage.
Give antibiotics if: Cellulitis, Systemic infection, Diabetes, Immunocompromised
patient, Prosthetic heart valve or high-risk cardiac condition

3. Pain Control
– NSAIDs or paracetamol
– Warm sitz baths
– Stool softeners
– High-fiber diet

4. Follow-Up
– Wound care
– Assess healing
– Evaluate for fistula-in-ano if persistent drainage develops

Important Note
Prompt surgical drainage is the treatment of choice. Antibiotics are an adjunct for selected patients and should never replace incision and drainage

Complications

– Fistula-in-ano (most common)
– Recurrent abscess
– Cellulitis
– Sepsis
– Delayed wound healing
– Necrotizing soft tissue infection (rare)

Prognosis

– Excellent after timely drainage
– Most patients recover completely
– Approximately one-third of patients develop a fistula
– Recurrence is more common in Crohn disease and immunocompromised patients

Key Points / Clinical Pearls

– Perianal abscess is usually caused by cryptoglandular infection.
– Severe constant anal pain is the hallmark symptom.
– Diagnosis is usually clinical.
– MRI is preferred for deep or recurrent abscesses.
– Incision and drainage is the definitive treatment.
– Antibiotics are only indicated for selected patients.
– Fistula-in-ano is the most common complication.
– Early treatment reduces the risk of recurrence and sepsis.