Sandbox: Reddy

Historical Perspective

• In 1880, Herman and Desfosses described the anal glands within the internal sphincter, sub-mucosa and their opening into the anal crypts and demonstrated that the infection of these glands and the spread of the infection through the intersphincteric space can result in the formation of a anal abscess.
• Tucker and Hellwig, provided evidence that the initial infection occurs in the anal ducts allowing the infection to spread from the anal lumen into the anal canal wall.
• In 1950, Goligher described the treatment for anal abscess with inicision and curettage with antibiotic bath and primary closure.

Classification

Based on the location of the abscess in relation to the anal canal and the spread of infection to the surrounding structures anal abscess can be classified into :

• Perianal abscess:When the infection reaches the anal verge passing between the internal and external sphincter, it results in the formation of a perianal abscess.
• Ischiorectal abscess:If the infection ruptures through the external sphincter it results in a formation of a ischiorectal abscess.
• Supralevator abscess:If the infection extends superiorly, it can form a supralevator abscess.
• Horseshoe abscess:Extension of the anal abscess to both the ischiorectal fossa results in the formation of a horseshoe abscess.

Based on the location the abscesses can also be classified into:

• High anorectal abscess: These include intersphincteric, perianal, and ischiorectal abscesses.
• Low anorectal abscess: These incude submucosal, supralevator abscesses.

Pathogenesis

• Anal canal is a 2 to 4cm in length, starts at the anorectal junction to the end of anal verge.
• It is divided into a upper and a lower part by transition zone that is seen at the dentate or pectinate line which is surrounded by longitudinal mucosal folds, called columns of morgagni.
• Each of this fold contains anal crypts, each of which contains 3 to 12 anal glands, the distribution of these glands is not uniform with most of the glands present anterior to the position of the anal canal and fewer in the posterior position.
• The initial infection occurs in the ducts of the anal glands and the spread of infection results in the formation of the abscess, various theories were put forward to describe the pathogenesis and the most accepted one is the cryptoglandular theory.
• The crytoglandular theory states that when a anal gland duct is obstructed, it results in a infection and due to the presence of these glands deep in relation to the anal canal and sphincter, the infection follows the path of least resistance resulting in a abscess formation at the termination of the gland.

Causes

• Supralevator abscess can be caused by the spread of infection from abdominal infections such as appendicitis, diverticulitis, or gynecologic sepsis.
• Spread of infection of ano-rectal Crohn's disease.
• Trauma to the anal canal
• Cancer of the anal canal or the anal glands

Epidemiology and Demographics

Incidence

• The incidence of anorectal abscess is estimated to be around 68,000 to 96,000 cases per year in the United States.

Gender

• Anal abscesses are two times more frequently seen in men than women.

Age

• Patients with anal abscess present between ages of 20 to 60 years with a mean age of 40 in both sexes.

Race

• There are limited epidemiological studies which studied the frequency of anal abscess with race differences, however a study in Chicago showed that 92% of the patients presented with anal abscess were African population.

Risk Factors

Risk factors for the development of recurrent of anal abscesses include

• Crohn disease
• Diabetes mellitus
• History of abscess in schiorectal location
• HIV infection

Differential Diagnosis

differentiated from other causes of anal pain including anal fissure, thrombosed hemorrhoids, levator spasm, sexually transmitted disease, proctitis, and cancer.

Diagnosis

History and Symptoms

• Patients with low abscess present with:
  • Anal pain
  • Pain with passing stools
  • Swelling
• Patients with high abscess present with :
  • Fever
  • Malaise
  • Anal pain

Physical Examination

• It is difficult to perform complete examination due to the severe pain and if a suspicion of a high abscess is present, patient should be examined under anesthesia to identify the location of the abscess.

Physical examination findings suggestive of anal abscess include:

• Erythema
• Warmth
• Tenderness
• Induration
• Fluctuance

Treatment

Surgical Therapy

• Management of anal abscess should be prompt as the risk of involving the surrounding tissue resulting in perineal cellulitis and sepsis is high.
• Therapy for anorectal abscess is incision and drainage.
• Patients with perianal abscess and ischiorectal abscess can be treated in a outpatient setting under local anesthesia using 1% lidocaine with epinephrine (and bupivacaine for extended analgesia), is injected subcutaneously into the area affected by the abscess to provide adequate infilteration into the skin.
• Patients with oculated or large ischiorectal, intersphincteric, supralevator, or horseshoe abscesses should be admitted to the hospital and the procedure should be performed under anesthesia.