An abscess is a localized collection of pus within a cavity formed due to tissue disintegration. It results from an infectious process, commonly caused by bacteria or parasites, or from the presence of foreign substances such as splinters or bullet wounds. The formation of an abscess represents a defensive mechanism by the immune system to confine the spread of infection.

Etiology and Pathophysiology

Pathogenesis of Abscess Formation

When microorganisms or foreign substances invade tissues, they trigger an intense inflammatory response. This response includes:

The release of cytokines and toxins from the invading pathogens and damaged cells.
Recruitment of a large number of white blood cells (WBCs) to the infection site.
Increased vascular permeability and regional blood flow, resulting in swelling and redness.

Over time, pus accumulates, consisting of:

Dead tissue cells destroyed by infection.
White blood cells that attempted to combat the infection.
Infectious agents (such as bacteria, parasites) or foreign substances.
Toxins produced by both the microorganisms and the body's immune response.

To prevent the infection from spreading further, adjacent healthy cells form an abscess wall, encapsulating the infected material and creating a protective barrier. However, if left untreated, the abscess can rupture or extend into deeper tissues, leading to serious complications such as systemic infection or septicemia.

Causes and Risk Factors

The main causes of abscesses include:

Bacterial infections:
Staphylococcus aureus (most common)
Streptococcus pyogenes
Escherichia coli (especially in intra-abdominal abscesses)
Mycobacterium tuberculosis (leading to cold abscesses)
Parasitic infections:
Entamoeba histolytica (causes amebic liver abscess)
Foreign bodies:
Splinters, bullet fragments, or surgical implants may introduce pathogens and lead to abscess formation.
Medical conditions that increase susceptibility:
Diabetes mellitus
Immunosuppression (e.g., HIV/AIDS, chemotherapy, steroid therapy)
Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis)
Poor hygiene and inadequate wound care

Clinical Features and Diagnosis

Signs and Symptoms

The characteristic signs of an abscess are derived from the cardinal signs of inflammation, including:

Redness (erythema)
Heat (warmth)
Swelling
Pain
Loss of function in the affected area

Superficial abscesses, such as those occurring in the skin, are easily identifiable due to localized swelling, tenderness, and visible redness. They may also be fluctuant, meaning they feel fluid-filled upon palpation.

Internal abscesses, such as those in the lungs, brain, or kidneys, may present with:

Deep-seated pain
Fever and chills
Generalized malaise or weight loss
Organ-specific symptoms (e.g., respiratory distress in a lung abscess)

If an abscess ruptures, it may lead to systemic complications like bacteremia, septicemia, or gangrene if the infection spreads to other tissues.

Diagnostic Approach

The evaluation of an abscess depends on its location:

Physical Examination:
Superficial abscesses are diagnosed through visual inspection and palpation.
Deep abscesses may require imaging for localization.

Imaging Studies:
Ultrasound: Useful for detecting fluid collections in soft tissues.
CT Scan: Essential for intra-abdominal abscesses, brain abscesses, and retroperitoneal abscesses.
MRI: Used in cases of spinal or deep organ abscesses.

Microbiological Tests:
Aspiration of pus for Gram staining and bacterial culture to identify the causative organism and guide antibiotic therapy.

Treatment and Management

General Treatment Principles

Most abscesses require incision and drainage (I&D), as antibiotics alone are generally ineffective in treating established pus collections.

Drainage Procedures

1. Surgical Drainage:

When an abscess softens and forms fluctuant pus, surgical lancing (incision and drainage) is the standard treatment.
The area is anesthetized, and a small incision is made to allow pus to drain.
The wound is kept open with packing material to promote continued drainage.

2. Percutaneous Drainage:

Used for deep abscesses (e.g., liver abscesses, abdominal abscesses, or pelvic abscesses).
Involves ultrasound- or CT-guided needle aspiration.

3. Non-Surgical Drainage:

In cases such as lung abscesses, postural drainage and coughing may help expel pus through the respiratory tract.

Antibiotic Therapy

Antibiotics are given in cases where:

The infection is severe or spreading.
There is associated cellulitis or systemic illness.
The abscess is located in a high-risk area (e.g., brain, heart valves).

Epidemiology and Prevention

Epidemiology

Skin abscesses are the most common type and have increased in prevalence due to community-acquired MRSA (CA-MRSA).
Organ-specific abscesses (e.g., liver, lung, brain) occur more frequently in immunocompromised individuals.
Intra-abdominal abscesses often develop postoperatively or secondary to diverticulitis, perforated appendicitis, or pancreatitis.

Prevention

To reduce the risk of abscess formation:

Proper wound care:
Clean wounds thoroughly and apply antiseptic.
Avoid picking at infected skin lesions.
Hand hygiene to prevent staphylococcal infections.
Control of chronic diseases:
Good glycemic control in diabetics to prevent recurrent skin abscesses.

Cold abscess

Abscesses caused by tuberculosis are called cold abscesses.

FAQS

Which locations do people get abscess(es)?

You can get an abscess almost anywhere in your body.

How does one get an abscess?

When an area of your body becomes infected, your body's immune system tries to fight the infection. White blood cells go to the infected area, collect within the damaged tissue, and cause inflammation. During this process, pus forms. Pus is a mixture of living and dead white blood cells, germs, and dead tissue.

Which organisms lead to abscess formation?

Bacteria, viruses, parasites and swallowed objects can all lead to abscesses.

Glossary of terms

This glossary provides definitions of various types of abscesses based on their location, cause, or characteristics.

A

Acute abscess – A rapidly developing abscess with intense inflammation, pain, and redness.
Alveolar abscess – An abscess located in the alveolar process of the jaw, commonly associated with dental infections.
Amebic abscess – A liver abscess caused by the protozoan parasite Entamoeba histolytica'.
Apical abscess – An abscess at the tip of a tooth root due to bacterial infection.
Appendiceal abscess – A localized collection of pus due to ruptured appendicitis.

B

Bartholin abscess – An abscess in the Bartholin's gland, typically due to obstruction and infection.
Bezold abscess – An abscess located in the neck, resulting from the spread of mastoiditis.
Bicameral abscess – A multi-chambered abscess, divided by septa.
Bone abscess – A collection of pus inside the bone, commonly associated with osteomyelitis.
Brain abscess – A localized collection of pus within the brain, often due to bacterial or fungal infections.
Brodie abscess – A chronic, localized bone abscess, often found in the long bones.
Bursal abscess – An abscess located in a bursa, usually due to chronic inflammation or infection.

C

Caseous abscess – An abscess containing caseous necrosis material, often seen in tuberculosis.
Caseous lymphadenitis – A chronic bacterial infection of the lymph nodes caused by Corynebacterium pseudotuberculosis.
Cheesy abscess – An abscess filled with thick, cheese-like material, similar to caseous abscesses.
Cholangitic abscess – An abscess occurring due to cholangitis, an infection of the bile ducts.
Chronic abscess – An abscess that develops over a prolonged period with less acute inflammation.
Collar stud abscess – A deep abscess that extends to the surface through a narrow tract.
Cold abscess – An abscess that lacks typical inflammatory signs such as heat and redness, often associated with tuberculosis.
Crypt abscesses – Small collections of pus in the intestinal crypts, characteristic of ulcerative colitis.

D

Dental abscess – A collection of pus within a tooth or surrounding structures.
Periapical abscess – Occurs at the tip of the tooth root due to untreated dental caries.
Periodontal abscess – Located in the supporting structures of the tooth.
Apical periodontal abscess – A periapical abscess at the apex of a tooth.
Lateral periodontal abscess – A periodontal abscess occurring along the side of the tooth.
Root abscess – Infection around the tooth root, usually due to trauma or decay.
Gingival abscess – A localized collection of pus in the gum tissue.
Lateral alveolar abscess – An abscess at the lateral aspect of the alveolar bone.
Pericoronal abscess – Occurs around a partially erupted tooth, commonly in wisdom teeth.
Combined periodontic-endodontic abscess – An abscess involving both the tooth root and periodontal structures.

E

Embolic abscess – An abscess resulting from a septic embolus.
Epidural abscess – An abscess occurring in the epidural space around the spinal cord or brain.

F

Fecal abscess – An abscess containing fecal material, often secondary to bowel perforation.
Follicular abscess – An abscess developing around a hair follicle.

G

Gas abscess – An abscess containing gas-producing bacteria, such as in gas gangrene.
Gravitation abscess – An abscess that extends downward due to gravity.
Gummatous abscess – A rare abscess occurring in tertiary syphilis.

H

Hematogenous abscess – An abscess resulting from hematogenous (blood-borne) spread.
Hidradenitis suppurativa – A chronic inflammatory condition involving abscess formation in sweat glands.
Hot abscess – An abscess with acute inflammatory signs, such as redness and heat.
Hypostatic abscess – An abscess forming in dependent areas due to poor circulation.

I

Ischiorectal abscess – An abscess occurring in the ischiorectal fossa, often related to perianal infections.

M

Mastoid abscess – An abscess associated with mastoiditis.
Metastatic abscess – An abscess occurring at a site distant from the primary infection.
Migrating abscess – An abscess that changes location over time.
Miliary abscess – Multiple small abscesses, commonly seen in septicemia.
Munro abscess – Collections of neutrophils in the epidermis, associated with psoriasis.

O

Orbital abscess – An abscess occurring in the orbit around the eye.
Otitic abscess – An abscess associated with ear infections.

P

Pancreatic abscess – A localized pus collection in the pancreas, often following acute pancreatitis.
Parapharyngeal abscess – An abscess located in the parapharyngeal space.
Peritonsillar abscess – A collection of pus near the tonsils, often seen in severe tonsillitis.
Pott abscess – A tuberculous abscess of the spine.
Psoas abscess – An abscess in the psoas muscle, often due to tuberculous spondylitis.

S

Septicemic abscess – An abscess resulting from bloodstream infection.
Sterile abscess – An abscess without bacterial infection, often due to irritants or injections.
Subdiaphragmatic abscess – An abscess beneath the diaphragm.
Subhepatic abscess – An abscess beneath the liver.
Subphrenic abscess – An abscess located below the diaphragm.
Suture abscess – An abscess forming around a retained surgical suture.

T

Tornwaldt abscess – An abscess in the nasopharyngeal bursa.
Tropical abscess – A deep-seated abscess seen in tropical regions, often due to bacterial infections.
Tubo-ovarian abscess – An abscess involving the fallopian tubes and ovaries, often due to pelvic inflammatory disease.

W

Wandering abscess – An abscess that migrates from its original site.
Worm abscess – An abscess caused by the presence of parasitic worms.

Abscess