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Perirectal or anorectal abscess is a condition in which an infection occurs in the tissues surrounding the rectum or anus. The infection results in the formation of a pus-filled pocket within the tissue. A channel (fistula) may also form leading from the abscess into other tissues, or into the rectum or anus. In some cases, the abscess can spread to both sides of the rectum or anus to form a horseshoe-shaped abscess.
There are four types of perirectal abscesses (perianal, ischiorectal, intersphincteric, supralevator) that are classified according to their location in the tissue. There are also four types of fistulas (intersphincteric, transsphincteric, extrasphincteric, suprasphincteric) that are classified according to their anatomic relationship to the muscles in the anus (anal sphincter). Notably, an intersphincteric abscess is always associated with a fistula.
Risk factors for perirectal abscess include diarrhea, physical trauma such as a hard stool or foreign body, injury such as a crack (fissure) in the anal tissue, Crohn's disease, an immune system that is not functioning well (immunocompromised), cancer (malignant neoplasm), hidradenitis suppurativa, tuberculosis, and pelvic infections such as diverticulitis or appendicitis. Other risk factors may include diabetes mellitus, blood disorders (dyscrasia), ulcerative colitis, chronic kidney (renal) failure, hemorrhoids, genitourinary infection, alcoholism, pregnancy, and a previous perirectal abscess or fistula.
The most common type of perirectal abscess is perianal (43% of all cases), followed by ischiorectal (23%), intersphincteric (21%), supralevator (7%), and unclassified abscess (6%). Fistula formation is most commonly associated with intersphincteric abscess (47% of cases), and less so with supralevator (43%), perianal (35%), and ischiorectal (25%).
Risk: While anorectal abscess can occur at any age, peak incidence is in the third to fourth decades of life with a male-to-female predominance of 2:1 to 3:1; approximately 30% of those who develop anorectal abscesses have a history of similar abscesses that either resolved spontaneously or required surgical intervention (Hebra). Incidence and Prevalence: There appears to be a seasonal component to the formation of anorectal abscess, with a higher incidence corresponding with the spring and summer seasons; a direct relationship between bowel habits, frequent diarrhea, and poor personal hygiene and the formation of anorectal abscesses has been suggested but remains unproven (Hebra). While there is a clear disparity with respect to age and sex noted in the occurrence of anal abscesses, no obvious pattern of incidence exists among various countries or regions of the world. |
Source: Medical Disability Advisor
History: Individuals will usually complain of pain and swelling in the area around the rectum (perirectal area), drainage of pus from the rectum or perirectum, fever, chills, constipation, and loss of appetite (anorexia). Other, less common, complaints may include weakness, dizziness, diarrhea, nausea and vomiting, difficult or painful urination (dysuria), a feeling of general discomfort (malaise), abdominal pain, itching around the perirectal area (perirectal pruritus), pain in the groin area (inguinal pain), sweating (diaphoresis), and sudden fainting (syncope). Physical exam: External physical examination usually reveals localized tenderness, redness (erythema), or swelling of the perirectal area. Insertion of a gloved finger into the anus (digital rectal examination) may reveal extreme tenderness and tightening (guarding) of the anal sphincter in response to touch. Severe pain during examination may necessitate regional or general anesthesia during this procedure. Digital rectal exam may also reveal a fistula opening if one is present. Digital rectal examination should be avoided in individuals whose immune systems are compromised because this procedure may lead to unwanted contamination of the blood with bacteria (bacteremia). In females, a pelvic examination may be helpful in making the diagnosis. Tests: Tests are not needed generally for the diagnosis. However, a complete blood count (CBC) with white blood cell differential may show an increase in the white blood cell count. A sample of pus from the abscess cavity may be tested for aerobic and anaerobic cultures. High-frequency sound waves (ultrasound) may be used to confirm and map out the extent of the abscess. Occasionally, insertion of a fiber-optic viewing microscope through the anus and into the rectum (proctosigmoidoscopy) may be helpful in diagnosis. |
Source: Medical Disability Advisor
Prompt surgical drainage under local or general anesthesia is the treatment for perirectal abscess. Drainage may be done by making an incision (radial stab incision). For abscesses that have spread to both sides of the perirectal area (horseshoe abscess), separate stab incisions may be made to allow complete drainage to occur. The wound may then be packed with medicated gauze, which can be removed 24 hours following the procedure. If a fistula is present, an incision (anal fistulotomy) may be made using an electrically-heated needle (electrocautery), which allows the fistula to heal.
Systemic, broad-spectrum antibiotics may be prescribed, although it has been suggested that they should not be used except in certain circumstances, such as for individuals with a biologic prosthesis (such as a hip prosthesis), pacemaker, or cardiac valve replacement; individuals who are immunocompromised (human immunodeficiency virus, or HIV; acquired immunodeficiency syndrome, or AIDS; and leukemia), or those who have received chemotherapy; individuals with an unusual degree of infection with the presence of gas-forming bacteria or inflamed connective tissue (cellulitis); and in individuals who are not able to receive immediate surgical drainage. |
Source: Medical Disability Advisor
Perirectal abscess that is treated using drainage (and in some cases antibiotics) usually heals promptly in otherwise healthy individuals. Restoration of normal rectal function may be expected in 85% to 90% of cases. Antibiotics alone are generally not effective in treating perirectal abscess. Without prompt drainage treatment, there is a high-risk of progression to a horseshoe abscess, and/or massive infection and tissue death (sepsis and necrosis). The mortality associated with sepsis can be as high as 40%. Recurrence rates of perirectal abscess following surgical drainage range from 35% to 95%; however, recent studies report recurrence rates as low as 30%. These same studies show that recurrence is generally high in individuals with diabetes mellitus (40%) or Crohn's disease (42%).
Three-fourths of individuals with recurrent perirectal abscess will also present with a persistent fistula. Uncontrollable intestinal gas (incontinence of flatus) occurs in individuals who have been treated for perirectal abscess approximately 5% to 10% of the time. Twenty percent of individuals who are treated for perirectal abscess will have incontinence of liquids and solids from the intestine. Finally, perirectal abscess in immunocompromised individuals is associated with mortality in 45% to 78% of cases. |
Source: Medical Disability Advisor
| To help the wound heal properly and to relieve discomfort, the use of stool softeners and frequent Sitz baths are helpful. Close follow-up and careful nursing of the wound by a physician/nurse team may be necessary to assist with dressing changes and monitor progress after surgery for complex fistulas. |
Source: Medical Disability Advisor
| Complications of perirectal abscess include progression of the infection to the point where tissue death occurs (necrotizing infection), spreading of the microbes into the bloodstream (bacteremia), and generalized infection of the blood and tissues (sepsis) that may lead to organ dysfunction (shock). Also, extensive anal and perianal skin infection (cellulitis) that is characterized by local heat, redness, pain, and swelling, and occasionally by fever, malaise, chills, and headache may occur. This may be accompanied by production of fetid gas just underneath the skin (crepitation), which is a surgical emergency. Perirectal abscess that is left untreated in immunocompromised individuals can be deadly. |
Source: Medical Disability Advisor
| Prolonged sitting, standing, or walking may be particularly uncomfortable until complete healing has occurred. Frequent breaks to avoid prolonged sitting, and close access to bathroom facilities may also be necessary until full recovery is achieved. Heavy physical labor may have to be restricted until recovery is complete. |
Source: Medical Disability Advisor
| If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case. Regarding diagnosis:
- Does individual have any risk factors for perirectal abscess such as diarrhea, rectal trauma, anal fissures, Crohn's disease, or immune suppression?
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What type of abscess and/or fistula does individual have?
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Was the diagnosis based on the findings in the physical exam?
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Were other conditions with similar symptoms (e.g., pilonidal sinus, hidradenitis suppurativa, colorectal cancer, diverticulitis, anal fistula, tubercular abscess, sebaceous cysts, actinomycosis, fissure-in-ano) considered in the differential diagnosis?
Regarding treatment:
- Was the abscess drained promptly as well as treating a fistula, if present?
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Was it necessary for individual to be on antibiotic therapy?
Regarding prognosis:
- Based on the treatment required and the underlying health of the individual, what was the expected outcome? Has adequate time elapsed for recovery?
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Does individual have existing conditions that could impact recovery and prognosis such as blood dyscrasia, heart disease, chronic renal failure, hemorrhoids, Crohn's disease, ulcerative colitis, diabetes, or previous treatment for perirectal abscess?
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Did individual experience any infectious complications such as cellulitis, or systemic infection that could impact recovery? Were the complications addressed promptly?
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Have appropriate work accommodations been made so individual can return to work safely?
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Source: Medical Disability Advisor
| CitedHebra, Andre, P. Thomas, and Michael DeWolf. "Perianal Abscess." eMedicine. Eds. Marc D. Basson, et al. 28 Jun. 2004. Medscape. 20 Dec. 2004 <http://emedicine.com/med/topic2733.htm>. |
Source: Medical Disability Advisor
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