Anorectal Abscess Management

Clinical Evaluation and Laboratory Tests

• A focused medical history and complete physical examination, including digital rectal examination, should be performed for patients with anorectal abscess, as recommended by the World Journal of Emergency Surgery 1
• Serum glucose, HbA1c, and urine ketones should be checked to identify undetected diabetes mellitus in patients with anorectal abscess 1
• Patients with systemic infection/sepsis should have complete blood count, serum creatinine, and inflammatory markers (such as CRP, procalcitonin, and lactates) checked 1

Imaging and Timing of Surgery

• Imaging should be reserved for atypical presentations, suspected supralevator abscesses, complex anal fistulas, or perianal Crohn's disease, with pelvic MRI being the gold standard for detailed assessment (76-100% accuracy) and contrast-enhanced pelvic MRI being the first-line imaging modality, as stated by the American Gastroenterological Association and the Journal of Crohn's and Colitis 2, 3, 1
• Endoscopic anorectal ultrasound (EUS) is a good alternative if rectal stenosis is excluded, and ultrasound is the preferred initial imaging modality to differentiate between hematoma and abscess, with characteristic features of abscesses including heterogeneous internal echoes, peripheral hyperemia, and posterior acoustic enhancement, as recommended by the American College of Radiology 3, 4
• The timing of surgery should be based on the presence and severity of sepsis, with outpatient management considered for fit, immunocompetent patients with small perianal abscess without systemic signs 1
• The following features can help differentiate between abscess and hematoma:

Surgical Approach

• Incision and drainage is the primary treatment for anorectal abscess, with surgical drainage being the cornerstone of treatment, as recommended by the World Journal of Emergency Surgery guidelines 1, 5
• For concomitant fistula, fistulotomy should only be performed for low fistulas not involving sphincter muscle, and a loose draining seton should be placed for fistulas involving sphincter muscle 1
• Probing to search for non-obvious fistulas should be avoided 1

Indications for Antibiotics and Pitfalls to Avoid

• Antibiotics should be administered in scenarios including presence of sepsis, surrounding soft tissue infection, immunocompromised patients, and disturbances of the immune response, covering Gram-positive, Gram-negative, and anaerobic bacteria, with a typical duration of 5-14 days based on clinical response, as recommended by the World Health Organization and the World Journal of Emergency Surgery guidelines 1, 5, 6, 7, 2, 8
• The European Crohn's and Colitis Organisation (ECCO) guidelines recommend metronidazole and ciprofloxacin for perianal abscesses, with usual daily doses of metronidazole 10-20 mg/kg and ciprofloxacin 20 mg/kg 9
• Patients with systemic signs of infection, such as temperature greater than 38.5°C or pulse greater than 100 beats per minute, should be considered for antibiotics, as recommended by the Infectious Diseases Society of America 10
• Significant surrounding cellulitis, defined as greater than 5 cm of erythema or induration, is an indicator for antibiotic consideration, according to the Infectious Diseases Society of America 10

Post-Operative Care and Follow-Up

• Proper wound care includes cleaning with warm water/saline 2-3 times daily, sitz baths, and non-adherent absorbent dressings, with consideration of alginate or hydrofiber dressings for deeper wounds, and regular follow-up is necessary to monitor for signs of recurrent abscess formation, development of fistula, delayed healing, and signs of infection, as suggested by the World Journal of Emergency Surgery and supported by other guidelines 1, 7, 2, 11
• First follow-up should be within 48-72 hours after drainage, and subsequent follow-ups every 1-2 weeks until complete healing, monitoring for signs of recurrent abscess formation, development of fistula, delayed healing, or persistent infection, with consideration of monitoring inflammatory markers (such as CRP and WBC count) and following trends in procalcitonin levels if initially elevated 1, 7, 8, 11

Special Considerations and Complications

• Inadequate initial drainage, presence of loculations, and delayed time from disease onset to incision are risk factors for recurrence, and underlying conditions, such as Crohn's disease or prosthetic joints, may also increase the risk of recurrence, with up to one-third of perianal abscesses manifesting a fistula-in-ano, increasing the risk of abscess recurrence, as supported by the World Journal of Emergency Surgery guidelines and other studies 5, 6, 1
• Long-term seton placement with medical therapy may be considered for complex fistulas in patients with Crohn's disease, tailored to the individual patient's needs and response to treatment, as recommended by the European Crohn's and Colitis Organisation (ECCO) guidelines 9
• Active luminal disease should be treated concurrently with surgical management, and for complex fistulas in Crohn's disease, infliximab, azathioprine, or 6-mercaptopurine, and antibiotics may be considered as initial treatment or maintenance therapy, as recommended by Gastroenterology 3, 12