Overview
Definition:
Incision and drainage (I&D) of a perianal abscess is a surgical procedure to evacuate purulent material from an infected collection of pus located near the anus or rectum
It is a cornerstone treatment for acute perianal abscesses, aiming to relieve pain, prevent spread of infection, and reduce the risk of complications.
Epidemiology:
Perianal abscesses are common, with an incidence of 1 in 1000 adults per year
They are more frequent in men than women and occur most commonly in individuals aged 20-40 years
Associated conditions like diabetes, inflammatory bowel disease (IBD), and immunosuppression increase the risk.
Clinical Significance:
Untreated perianal abscesses can lead to serious complications including anal fistula formation, recurrent abscesses, sepsis, and even necrotizing fasciitis
Prompt and effective I&D is crucial for patient recovery and preventing long-term sequelae, making it a vital skill for surgical residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Severe, constant perianal pain, often described as throbbing
Pain may worsen with defecation, sitting, or coughing
Swelling and tenderness in the perianal region
Fever, chills, and malaise may be present
Difficulty or inability to defecate due to pain
Purulent discharge may be noted if the abscess has spontaneously ruptured.
Signs:
A tender, erythematous, fluctuant mass palpable in the perianal area
Erythema and edema of the overlying skin
Tenderness on digital rectal examination
In some cases, a visible external opening may be present
Vital signs may show fever or tachycardia in more severe cases.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on a history of characteristic pain and physical examination revealing a tender perianal mass
Imaging (ultrasound, CT, MRI) may be used to confirm the diagnosis, delineate the extent of the abscess, and identify associated fistulous tracts, especially in complex or recurrent cases, or when physical examination is equivocal.
Diagnostic Approach
History Taking:
Detailed history focusing on onset and character of pain
Previous history of perianal abscess, fistula, or surgery
Presence of systemic symptoms (fever, chills)
History of IBD, diabetes, or immunocompromise
Recent antibiotic use
Sexual history (risk of STIs).
Physical Examination:
Thorough external perianal inspection for erythema, edema, and visible masses
Palpation for tenderness, induration, and fluctuation
Digital rectal examination (DRE) to assess for an internal component of the abscess, assess rectal tone, and identify associated fistulous openings or induration
Examination under anesthesia (EUA) may be necessary for complete assessment and definitive management, especially for deeper or complex abscesses.
Investigations:
Blood tests: Complete blood count (CBC) to assess for leukocytosis
erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) for inflammation
Blood cultures if sepsis is suspected
Imaging: Perianal ultrasound is highly sensitive for detecting abscesses and guiding drainage
CT scan or MRI may be useful for complex cases, deep abscesses, or to evaluate for associated fistulas or complications
Stool studies may be considered if infectious proctitis is suspected.
Differential Diagnosis:
Pilonidal sinus, anal fissure (though typically less indurated), hemorrhoids (especially thrombosed), hidradenitis suppurativa, Bartholin's cyst (in females), diverticulitis with a perianal complication, soft tissue infections (e.g., cellulitis), and perirectal tumors.
Management
Initial Management:
Immediate pain relief with analgesics
Sitz baths to promote comfort and drainage
Antibiotics may be prescribed for cellulitis or systemic symptoms, but are generally not a substitute for drainage in established abscesses
Prompt surgical referral is essential.
Medical Management:
Antibiotics are usually reserved for patients with associated cellulitis, significant systemic symptoms, or those who are immunocompromised
Broad-spectrum antibiotics covering gram-negative and anaerobic bacteria are typically used (e.g., ciprofloxacin + metronidazole, or amoxicillin-clavulanate)
Doses depend on severity and patient factors.
Surgical Management:
Indications: Confirmed perianal abscess with fluctuance
Management involves incision of the abscess cavity, complete evacuation of pus, and exploration to ensure adequate decompression
Techniques include: Linear incision over the point of maximal fluctuance, often extending superiorly along the expected tract
cruciate incision
The wound is typically left open to heal by secondary intention or packed loosely with gauze
For intersphincteric or ischiorectal abscesses, EUA is often required
Management of associated fistulas (e.g., fistulotomy) is usually deferred to a later date once the acute infection has resolved, unless a simple low-lying horseshoe abscess is present.
Supportive Care:
Postoperative pain management is crucial
Regular wound care, including sitz baths, is recommended
Packing changes as needed
Monitoring for signs of recurrent infection, sepsis, or fistula development
Adequate hydration and nutrition
Stool softeners to prevent straining
Education on hygiene and recognizing signs of complications.
Complications
Early Complications:
Inadequate drainage leading to recurrent abscess formation
Spread of infection (cellulitis, necrotizing fasciitis, pelvic sepsis)
Bleeding from the wound
Pain
Injury to the anal sphincter causing incontinence.
Late Complications:
Anal fistula formation (most common complication, occurring in up to 50% of cases)
Chronic anal pain
Scarring
Rectal stricture (rare)
Recurrent abscesses.
Prevention Strategies:
Adequate and complete surgical drainage is paramount
Thorough exploration of the abscess cavity to identify all loculations
Careful identification and management of any associated fistulous tracts (often deferred)
Prompt treatment of underlying conditions (e.g., IBD, diabetes)
Patient education on wound care and follow-up.
Prognosis
Factors Affecting Prognosis:
The presence of underlying conditions like IBD or immunosuppression
The complexity and location of the abscess
The adequacy of the initial drainage
Development of anal fistulas
The patient's overall health status.
Outcomes:
With prompt and complete surgical drainage, most patients experience significant pain relief and resolution of acute symptoms
The primary concern for long-term prognosis is the development of an anal fistula, which may require further surgical intervention
Recurrence rates vary but are higher in patients with underlying conditions.
Follow Up:
Regular follow-up is essential to monitor wound healing, assess for signs of recurrence, and evaluate for the development of anal fistulas
Follow-up appointments are typically scheduled at 1-2 weeks post-operatively and then as needed
Patients should be educated to report any new or worsening pain, fever, or discharge immediately.
Key Points
Exam Focus:
The majority of perianal abscesses are caused by infection of the anal crypts
The horseshoe abscess is a common and challenging type
Intersphincteric and ischiorectal abscesses often require examination under anesthesia for adequate drainage
Anal fistula formation is the most common sequela and requires careful consideration for future management.
Clinical Pearls:
Always consider examination under anesthesia (EUA) for complete assessment and definitive treatment, especially for deeper or complex abscesses
Do not be afraid to explore the wound thoroughly to ensure complete evacuation
Remember that antibiotics alone are rarely sufficient for treating an established abscess
Post-operative pain management is critical for patient comfort and compliance with wound care.
Common Mistakes:
Inadequate drainage, leading to recurrent abscess or fistula
Failure to consider EUA when indicated
Over-reliance on antibiotics without surgical intervention
Not recognizing the high incidence of fistula formation and its implications for long-term management
Discharging patients without adequate follow-up instructions.