What is the appropriate treatment for a patient with a rectal abscess, potentially with underlying conditions such as diabetes, immunocompromised states, or history of gastrointestinal diseases like Crohn's disease or ulcerative colitis?

Treatment of Rectal Abscess

Immediate Surgical Drainage is Mandatory

Incision and drainage is the definitive and only effective treatment for rectal abscess—antibiotics alone will fail and allow progression to deeper, life-threatening infection. 1, 2

Timing of Surgical Intervention

The urgency of drainage depends on specific patient factors:

Emergency Drainage (Within Hours)

Perform immediate surgical drainage for patients with: 1, 3

• Sepsis, severe sepsis, or septic shock
• Immunosuppression (including steroid use, HIV, chemotherapy)
• Diabetes mellitus (check serum glucose, HbA1c, and urine ketones in all patients to identify undetected diabetes) 4
• Diffuse cellulitis surrounding the abscess

Urgent Drainage (Within 24 Hours)

For patients without the above high-risk features, perform drainage within 24 hours of diagnosis. 1

Critical caveat: Symptoms are frequently absent or diminished in elderly, debilitated, diabetic, or immunosuppressed patients—maintain high suspicion and use an aggressive approach in these populations. 4

Diagnostic Approach

Clinical Examination

• Perianal pain (present in 98.9% of cases) with constant throbbing quality is the hallmark symptom 2, 5
• Perform digital rectal examination, which identifies 94.6% of abscesses 5
• Examine for surgical scars, anorectal deformities, signs of perianal Crohn's disease, cellulitis, or external fistula openings 4

When to Order Imaging

Do not delay drainage if imaging is unavailable when abscess is clinically suspected. 1 However, consider imaging for: 4, 1

• Atypical presentation (lower back pain, severe anal pain without fissure, urinary retention)
• Suspected supralevator or intersphincteric abscess
• Suspicion of perianal Crohn's disease
• CT scan is preferred in emergency settings due to short acquisition time and widespread availability 4

Laboratory Testing

• Check complete blood count, serum creatinine, inflammatory markers (CRP, procalcitonin, lactate) in patients with signs of systemic infection 4
• Mandatory screening for diabetes in all patients: serum glucose, HbA1c, urine ketones 4

Surgical Technique

Incision Placement and Drainage

• Keep the incision as close as possible to the anal verge to minimize potential fistula length while ensuring adequate drainage 1, 3
• Complete drainage is essential—inadequate drainage leads to recurrence rates up to 44% 1, 3
• For large abscesses, use multiple counter incisions rather than a single long incision to avoid step-off deformity 1
• Send drained pus for culture, especially in high-risk patients or those with risk factors for multidrug-resistant organisms 3

Management of Concomitant Fistulas

Do not probe for or attempt to treat fistulas during emergency drainage. 3 If an obvious fistula is identified: 1, 3

• Low fistulas not involving sphincter muscle: Perform fistulotomy at time of drainage
• Fistulas involving any sphincter muscle: Place a loose draining seton only

Antibiotic Therapy

Antibiotics are NOT routinely required after adequate surgical drainage in immunocompetent patients. 1, 2

Indications for Antibiotics

Use empiric broad-spectrum coverage (Gram-positive, Gram-negative, and anaerobic bacteria) only for: 1, 3

• Sepsis and/or surrounding soft tissue infection
• Immunocompromised status
• Incomplete source control or significant cellulitis
• Diabetes mellitus with systemic signs

Special Considerations for Underlying Conditions

Crohn's Disease Screening

It is mandatory to exclude underlying Crohn's disease, especially with recurrent abscesses. 4, 2 Assess for:

• Inflammatory bowel disease symptoms (diarrhea, weight loss, abdominal pain)
• Previous anorectal procedures or deformities
• If Crohn's disease is suspected or confirmed, perform endoscopic assessment of the rectum—proctitis predicts persistent non-healed fistula tracts and higher proctectomy rates 1

High-Risk Populations

Risk factors for reoperation and readmission include: 6

• Morbid obesity
• Female sex
• Steroid/immunosuppression use
• Dependent functional status
• Preoperative sepsis

Post-Operative Management

• The role of wound packing remains controversial—some evidence suggests it may be costly and painful without adding benefit 1
• Routine imaging after drainage is not required 1
• Consider follow-up imaging only for recurrence, suspected inflammatory bowel disease, or evidence of fistula/non-healing wound 1

Life-Threatening Complications

Undrained perianal abscess can expand into adjacent spaces and progress to necrotizing soft-tissue infection with 40% mortality. 1, 7 This emphasizes the absolute necessity of timely, complete surgical drainage rather than reliance on antibiotics alone.