A localised collection of pus. A minute abscess is known as a PUSTULE; a diﬀused production of pus is known as CELLULITIS or ERYSIPELAS. An abscess may be acute or chronic. An acute abscess is one which develops rapidly within the course of a few days or hours. It is characterised by a deﬁnite set of symptoms.
Causes The direct cause is various BACTERIA. Sometimes the presence of foreign bodies, such as bullets or splinters, may produce an abscess, but these foreign bodies may remain buried in the tissues without causing any trouble provided that they are not contaminated by bacteria or other micro-organisms.
The micro-organisms most frequently found are staphylococci (see STAPHYLOCOCCUS), and, next to these, streptococci (see STREPTOCOCCUS) – though the latter cause more virulent abscesses. Other abscess-forming organisms are Pseudomonas pyocyanea and Escherichia coli, which live always in the bowels and under certain conditions wander into the surrounding tissues, producing abscesses.
The presence of micro-organisms is not sufﬁcient in itself to produce suppuration (see IMMUNITY; INFECTION); streptococci can often be found on the skin and in the skin glands of perfectly healthy individuals. Whether they will produce abscesses or not depends upon the virulence of the organism and the individual’s natural resistance.
When bacteria have gained access – for example, to a wound – they rapidly multiply, produce toxins, and cause local dilatation of the blood vessels, slowing of the bloodstream, and exudation of blood corpuscles and ﬂuid. The LEUCOCYTES, or white corpuscles of the blood, collect around the invaded area and destroy the bacteria either by consuming them (see PHAGOCYTOSIS) or by forming a toxin that kills them. If the body’s local defence mechanisms fail to do this, the abscess will spread and may in severe cases cause generalised infection or SEPTICAEMIA.
Symptoms The classic symptoms of inﬂammation are redness, warmth, swelling, pain and fever. The neighbouring lymph nodes may be swollen and tender in an attempt to stop the bacteria spreading to other parts of the body. Infection also causes an increase in the number of leucocytes in the blood (see LEUCOCYTOSIS). Immediately the abscess is opened, or bursts, the pain disappears, the temperature falls rapidly to normal, and healing proceeds. If, however, the abscess discharges into an internal cavity such as the bowel or bladder, it may heal slowly or become chronic, resulting in the patient’s ill-health.
Treatment Most local infections of the skin respond to ANTIBIOTICS. If pus forms, the abscess should be surgically opened and drained.
Abscesses can occur in any tissue in the body, but the principles of treatment are broadly the same: use of an antibiotic and, where appropriate, surgery.