Anorectal Abscess - Causes, Symptoms, Diagnosis, Treatment, and Prevention

Introduction

An abscess is a collection of pus that can occur in any part of the body internally or externally and causes pain. When the abscess is formed externally on the skin, it is visible, and other characteristics such as skin discoloration, swelling, discharges, etc., are visible. If an abscess is formed within the internal structures or spaced between the organs, it becomes difficult to diagnose and manage.

An anorectal abscess is a type of abscess that occurs in the anal or rectum region. It is located at the junction between the anal canal and the outside skin. This junction is called the anal verge and can be physically seen. Therefore, a physical examination or digital rectal exam is the best diagnostic tool for this condition. Generally, an abscess is treated by draining out the pus to give immediate relief from the pain and enhance the healing process.

What Is an Anorectal Abscess?

An anorectal abscess is a collection of pus due to a bacterial infection that causes pain in the anal or rectum region. The other names of an anorectal abscess may include perianal abscess, rectal abscess, gland abscess, or anal abscess. It is located at the junction between the anal canal and outside skin - the anal verge.

What Causes an Anorectal Abscess?

• Clogging or blocking of anal glands.

• Bacterial infection in the clogged gland.

• Infection of the anal fissure - Tearing of the inner lining of the anal canal.

• Sexually transmitted disease.

• Inflammatory bowel disease.

• Trauma or injury.

• Malignancy.

What Is the Pathophysiology of an Anorectal Abscess?

An abscess occurs because of a bacterial infection in the anal gland or anal sac (oval or round-shaped small glands present inside the anus or near the opening of the anus). During the excretion or passing of the stool, these glands become empty. If these glands are not emptied fully, then small pits in the anal canal become infected. These small pits are called anal crypts or crypts of Morgagni. As the infection develops, it spreads into various spaces such as perianal space, perirectal space, etc. The skin and space around the anus is the perianal space, extending up to the fats of the buttocks.

Which Bacteria Causes an Anorectal Abscess?

The common bacteria that causes anorectal abscess are:

• Bacteroides fragilis.

• Peptostreptococcus.

• Fusobacterium.

• Prevotella.

• Staphylococcus aureus.

• Clostridium.

• E.coli.

• Streptococcus.

What Are the Symptoms of an Anorectal Abscess?

The patient may suffer from:

• Pain in the anal region.

• Fever and chills.

• Constipation.

• Bleeding and pus discharge from the abscess.

How to Diagnose an Anorectal Abscess?

Anorectal abscess diagnosis includes the following methods:

1. Medical History: The patient may give a history of dull, sharp, shooting, or throbbing (regular, strong) pain in the anal region.

2. Physical Examination: The doctor must examine the affected area for a suspected case of piles. Discharge or bleeding may be visible from the abscess. The area may look red and swollen. Digital rectal examination is done with the help of a speculum, an instrument used to see the inside structures through the expansion of the instrument.

3. Imaging Test: Computed tomography may not be very helpful if the affected area or abscess is very small. Thus, magnetic resonance imaging is preferred over computed tomography.

4. Blood Test: Complete blood count (CBC) may show increased levels of white blood cells.

How to Treat an Anorectal Abscess?

1) Incision and Drainage: An immediate treatment approach for an anorectal abscess is incision and drainage to relieve the pain and support the healing process. In this procedure:

• Local anesthesia is given to the patient. Generally, one percent Lidocaine.

• An incision or cut is made close to the anal verge.

• The infected fluid (pus) from the abscess is drained out completely.

• The wound is packed to allow a natural healing process to occur.

2) Antibiotic Therapy: Antibiotics are prescribed to treat bacterial infection after drainage. Prescribing antibiotics without incision and drainage may not help in treating an anorectal abscess.

Which Antibiotics Are Used to Treat Anorectal Abscess?

Ciprofloxacin, Metronidazole, Ampicillin, etc., are the commonly used antibiotics to treat anorectal abscess.

What Are the Complications of Anorectal Abscess?

An anorectal abscess may lead to:

• Sepsis - A response of the body in which it damages its tissues.

• Formation of Fistula - Abnormal connection between the organs or body structures.

• Recurrence of the Abcess - The abscess may recur after the remission.

• Fecal Incontinence - Leakage of stool.

What Is the Difference Between Anorectal Abscess and Perirectal Abscess?

A perirectal abscess is a deep infection located in the pelvis region. An anorectal abscess is not a deep infection in the skin and is located in the anal region.

What Should Be Postoperative Care After Anorectal Abscess Treatment?

Once the patient is discharged from the hospital, he/she must follow self-care instructions such as:

• Take a high fiber diet to avoid constipation.

• Take antibiotics and pain relievers as prescribed.

• Keep the abscess area clean.

• Take a sitz bath to relieve pain. It is a bath in warm and shallow water.

• Keep proper follow-up with the doctor till the abscess is completely healed to avoid further complications or recurrence of the abscess.

How to Prevent Anorectal Abscess?

The patient must:

• Maintain cleanliness in the perianal area.

• Take proper and timely treatment of the underlying cause or risk factors such as diabetes, sexually transmitted disease, inflammatory bowel disease, trauma or injury, malignancy, etc.

Which Doctor Is Best to Treat an Anorectal Abscess?

It is best to see a general surgeon or colorectal surgeon. If a specialist is not available, then the patient must see a physician.

What Is the Differential Diagnosis of Anorectal Abscess?

The symptoms of an anorectal abscess may mimic the following conditions:

• Trauma or injury to the tissues of the anal region.

• Anal fissure (tearing of the inner lining of the anal canal).

• Anal fistula (an abnormal connection between bowel and anus).

• Thrombosis of external hemorrhoids (blood clot formation in the external hemorrhoids, bumps in the skin around the anus).

• A pilonidal cyst (abnormal formation of the cyst or pocket from hair follicles and skin).

• Cellulitis (discoloration of the skin due to bacterial infection).

• Bartholin’s abscess (abscess formation near the vagina).

• Cancer.

• Proctitis (inflammation of the rectum lining).

• Ulcerative colitis (ulcer formation and inflammation of the digestive tract).

How Long Does It Take for an Anorectal Abscess to Heal?

It takes up to eight weeks to completely heal the anorectal abscess. If the patient is healthy and does not have an underlying disease, then the prognosis is good, and the mortality or disease rate is low. If the anorectal abscess is left untreated or is diagnosed late, then it may result in life-threatening conditions such as Fournier’s gangrene (an infection of the scrotum and penis).

Conclusion

An anorectal abscess is a treatable condition through a surgical incision and drainage because it occurs due to bacterial infection in the anal glands leading to pus formation in the skin of the anal region. If diagnosed early and treated promptly, it shows good health outcomes in a healthy patient. Most commonly, a physical examination and digital rectal exam help diagnose the condition. It is best to prevent the occurrence of an abscess by maintaining good personal hygiene.