Pathophysiology of abscess formation

Introduction: Abscess can form on the skin or within the body in response to tissue injury and cell death, which has been invaded by a pyogenic microorganism. An abscess, basically, contains pus. Then depending on the nature of the abscess, the pus can be creamy or of caseous type.  

Definition: An abscess can be defined as a localized collection of pus in a cavity that is caused by pyogenic microorganism, usually infectious bacteria, following tissue damage.

Sites of abscess formation: Primarily, the site of abscess formation can be divided into two.

a)      External abscess:  for instance an abscess on the skin surface

b)      Internal abscess:  For instance, brain abscess, liver abscess, kidney abscess among others.

Atiology of abscess: the cause of abscess is infection/invasion of damaged/broken tissue by pyogenic microorganisms like Staphylococci or streptococci.

Pathophysiology/Mechanism of abscess formation

tissue damage or destruction  which can be as a result of trauma/accident, surgical procedures, parasitic larva migrant, occult origin among others leads to inflammation which can be acute or chronic . The inflammation is characterized by the cardinal signs of inflammation (Pain, swelling, heat, and redness). The damage tissue and the accompanied cell death lead to decrease oxygen concentration. The anaerobic environment favors the proliferation of pyogenic microorganisms. Some of these microorganisms are normal flora of the body like Staphylococci species, Streptococci Species, and Bacteroides  fragilis  which invade the tissues after injury.

These organism produce virulence factors that aid its pathogencity. For instance Bacteroides  fragilis  release virulence factors that helps it to tolerate oxygen, antibiotic inactivating enzymes etc.  Moreover, the anaerobic environment works against the host immune system and the activity of antimicrobial agents.

The damage tissue causes the release of cytokins which initates and promotes immune response to the affected area. Consequently, white blood cells (mostly Neutrophils) migrate to the site of injury to combat the invading microorganism.

The body forms fibrous capsule around the dead tissues to protect the healthy tissues and prevent the spread of the infectious agents. Consequently, pus accumulates within the cavity, produced by dead tissues, and surrendered by fibrous capsule leading to the formation of an Abscess.

Consequently, an abscess, can be said to, have three component parts. There are

a)      A cavity which contains the pus

b)      Pus which consists of dead tissues, dead bacteria/microorganism, leucocytes, and extracellular fluid.

c)       Fibrous capsule which is a delimiting membrane that helps to prevent the spread of the microorganism/pus.

Treatment: this is by the administration of antimicrobial agents and antihistamine to kill the infectious agent and control inflammation respectively. This is important to prevent the pus from entering the systemic circulation thereby leading to spread of infection and complications.

Conclusion:  abscess usually forms following the contamination of wounds by infectious microorganisms. That is the main reason aseptic surgery is vital and the treatment and management of wounds are important to prevent abscess formation and spread of infectious agents.

Lastly, a chronic form of inflammation can lead to the production of caseous abscess. This type of abscess is usually firm because it contains little or no fluid and may contain some mineral deposits like calcium.

Reference:

http://www.britannica.com/EBchecked/topic/1701/abscess

http://www.ncbi.nlm.nih.gov/pubmed/6872404

http://www.scribd.com/doc/53049965/What-Is-the-Pathophysiology-of-an-Abscess

http://www.webmd.com/a-to-z-guides/abscess

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