An abscess results from pus gathering in a tissue of the body that has formed a cavity due to an infection. The pathophysiology of an abscess is a series of immune responses beginning with the migration of white blood cells to the infection and the separation of a fluid-filled cavity from the surrounding, healthy tissue. Some abscesses result from blocked ducts in glands, while others are caused by infected injuries, frequently by the bacterium Staphylococcus aureus.
The pathophysiology of abscesses begins in damaged tissue when the immune system prevents foreign substances and potentially harmful microorganisms from spreading. During infection, large numbers of white blood cells, particularly neutrophils, migrate to compromised tissue. They do this following signals from cytokines that alert them to cell death and injury. Pus, the mixture of dead cells and the chemical mediators of immune response, fills the area around the site, which is separated from healthy tissue by the formation of an abscess wall. The pathophysiology of an abscess can cause life-threatening consequences if cavities form in organs like the liver.
In an epidural abscess, pus accumulates above the outer dural membrane that covers the brain and spine, swelling against the cranium or vertebral column. These rare infections are likelier along the spinal cord than in the skull. The pathophysiology of an abscess in the cranium or spine is often complicated by the damage done to neural tissue by fluid pressure as swelling increases. A tooth abscess comes from a local infection in the jaw, around the nerve that makes up the dental root. It causes intense pain, and if ruptured, can send bacteria into the bloodstream, risking systemic infection.
Blockage of glands can seal off an area of tissue that enables an abscess to form if infected. Different microorganisms can trigger the pathophysiology of Bartholin's abscess, a painful swelling in a Bartholin's gland in the vagina. If the glands, responsible for healthy vaginal secretions, develop a blocked duct, fluid can accumulate over time. Bacteria may then infect the swollen gland to the point that it becomes very sensitive. Similarly, skin abscesses or boils can arise from a blocked sweat gland that has become infected.
Differences in the pathophysiology of an abscess do not greatly influence basic treatment. Since Staphylococcus aureus commonly causes abscesses, traditional antibiotic treatments have accompanied surgery as the two mainstays of medical care. But as this organism has evolved into methicillin-resistant Staphylococcus aureas (MRSA), the range of antibiotics used to reduce complications has been increased. Many abscesses, particularly larger ones, will require surgical treatment to drain the existing pus from the wound for proper healing. This is often true regardless of the specific cause of infection.