Makindo Medical Notes

Perianal abscesses and fistulae are common conditions affecting the anal and rectal region. They result from infection and inflammation of the anal glands and crypts. If left untreated, abscesses can evolve into fistulae, which are abnormal connections between the anal canal and perianal skin.

Perianal Abscess

A perianal abscess is a localized infection in the perianal region, resulting from an infected anal gland. It forms a pus-filled cavity near the anus, and if not drained, it may rupture or form a fistula.

Causes

• Cryptoglandular infection: Blockage and infection of the anal glands within the anal crypts.
• Inflammatory bowel disease (IBD): Especially in Crohn's disease, patients may develop perianal abscesses.
• Trauma: Injury or surgeries around the anorectal region can predispose to infection.
• Immunosuppression: HIV, diabetes, or other conditions impairing immunity increase the risk of abscess formation.

Clinical Features

• Pain: Severe, constant, throbbing pain near the anus, often worse when sitting.
• Swelling: Tender, fluctuant mass in the perianal area.
• Redness and warmth: Over the affected area.
• Fever: May occur in more severe infections.
• Pus drainage: Spontaneous rupture may lead to pus discharge.

Diagnosis

• Clinical Examination: Physical inspection and digital rectal examination can identify the abscess.
• Imaging: In cases of deeper abscesses, pelvic MRI or ultrasound can help with localization.

Management

• Incision and Drainage (I&D): The mainstay of treatment. The abscess is surgically drained to relieve symptoms and prevent fistula formation.
• Antibiotics: Not always required but can be used in immunocompromised patients or those with systemic signs of infection (fever, sepsis).
• Analgesia: Pain relief with NSAIDs or opioids in more severe cases.
• Follow-up: Patients should be monitored for potential fistula formation, which may develop in 30-50% of cases after drainage.

Perianal Fistula

A perianal fistula is an abnormal tract that forms between the anorectal canal and the perianal skin. It typically follows an abscess and may become chronic if not treated properly.

Causes

• Post-abscess: The most common cause, following improper or inadequate drainage of a perianal abscess.
• Inflammatory bowel disease (IBD): Particularly Crohn’s disease is a major risk factor for fistula formation.
• Trauma: Injury to the perianal region can lead to fistula formation.
• Infection: Chronic infection in the anal glands or surrounding tissues can cause fistulae.

Clinical Features

• Recurrent abscesses: Episodes of swelling and drainage of pus from the perianal area.
• Discharge: Persistent or intermittent discharge of pus or fecal material from an external opening in the skin near the anus.
• Pain: May be associated with infection of the fistula tract.

Classification: classified based on their relationship to the anal sphincter muscles

• Intersphincteric: Most common type, running between the internal and external sphincters.
• Transsphincteric: Passes through both the internal and external sphincter muscles.
• Suprasphincteric: Travels over the top of the external sphincter.
• Extrasphincteric: Rare type that passes completely outside the sphincter muscles.

Diagnosis

• Clinical Examination: Identifying an external opening and performing a digital rectal exam.
• Imaging: MRI or endoanal ultrasound can help delineate the fistula tract.
• Probing: Under anesthesia, a probe may be inserted into the fistula to identify its course.

Management

• Surgical Treatment: The definitive treatment for a fistula is surgery.
  • Fistulotomy: The tract is surgically opened to heal from the inside out. Suitable for simple, low fistulas.
  • Seton Placement: A thread is placed through the fistula to allow drainage and prevent premature closure. Often used for complex fistulas.
  • Advancement Flap: A procedure where the internal opening of the fistula is covered with a flap of healthy tissue.
  • LIFT (Ligation of Intersphincteric Fistula Tract): A sphincter-sparing technique where the fistula tract is ligated.
• Antibiotics: May be used in patients with IBD or in cases with active infection.
• Analgesia: Pain relief with NSAIDs or opioids as needed.
• Stool Softeners: May be prescribed to avoid straining during bowel movements.

Conclusion

Perianal abscesses and fistulae are closely related conditions caused by infection of the anal glands. Early identification and treatment of abscesses can prevent fistula formation. Fistulae often require surgical intervention for definitive management, and various techniques are available based on the complexity of the fistula. Accurate diagnosis, imaging, and appropriate surgical management are key to ensuring optimal outcomes and minimizing complications.