Manual of Surgery Volume First: General Surgery. Sixth Edition.

by Alexis Thomson; Alexander Miles

Any tissue of the body may be the seat of an acute abscess, and there are many routes by which the bacteria may gain access to the affected area. For example: an abscess in the integument or subcutaneous cellular tissue usually results from infection by organisms which have entered through a wound or abrasion of the surface, or along the ducts of the skin; an abscess in the breast from organisms which have passed along the milk ducts opening on the nipple, or along the lymphatics which accompany these. An abscess in a lymph gland is usually due to infection passing by way of the lymph channels from the area of skin or mucous membrane drained by them. Abscesses in internal organs, such as the kidney, liver, or brain, usually result from organisms carried in the blood-stream from some focus of infection elsewhere in the body.

A knowledge of the possible avenues of infection is of clinical importance, as it may enable the source of a given abscess to be traced and dealt with. In suppuration in the Fallopian tube (pyosalpynx), for example, the fact that the most common origin of the infection is in the genital passage, leads to examination for vaginal discharge; and if none is present, the abscess is probably due to infection carried in the blood-stream from some primary focus about the mouth, such as a gumboil or an infective sore throat.

The exact location of an abscess also may furnish a key to its source; in axillary abscess, for example, if the suppuration is in the lymph glands the infection has come through the afferent lymphatics; if in the cellular tissue, it has spread from the neck or chest wall; if in the hair follicles, it is a local infection through the skin.

Formation of an Abscess.—When pyogenic bacteria are introduced into the tissue there ensues an inflammatory reaction, which is characterised by dilatation of the blood vessels, exudation of large numbers of leucocytes, and proliferation of connective-tissue cells. These wandering cells soon accumulate round the focus of infection, and form a protective barrier which tends to prevent the spread of the organisms and to restrict their field of action. Within the area thus circumscribed the struggle between the bacteria and the phagocytes takes place, and in the process toxins are formed by the organisms, a certain number of the leucocytes succumb, and, becoming degenerated, set free certain proteolytic enzymes or ferments. The toxins cause coagulation-necrosis of the tissue cells with which they come in contact, the ferments liquefy the exudate and other albuminous substances, and in this way pus is formed.

If the bacteria gain the upper hand, this process of liquefaction which is characteristic of suppuration, extends into the surrounding tissues, the protective barrier of leucocytes is broken down, and the suppurative process spreads. A fresh accession of leucocytes, however, forms a new barrier, and eventually the spread is arrested, and the collection of pus so hemmed in constitutes an abscess.

Owing to the swelling and condensation of the parts around, the pus thus formed is under considerable pressure, and this causes it to burrow along the lines of least resistance. In the case of a subcutaneous abscess the pus usually works its way towards the surface, and “points,” as it is called. Where it approaches the surface the skin becomes soft and thin, and eventually sloughs, allowing the pus to escape.

An abscess forming in the deeper planes is prevented from pointing directly to the surface by the firm fasciæ and other fibrous structures. The pus therefore tends to burrow along the line of the blood vessels and in the connective-tissue septa, till it either finds a weak spot or causes a portion of fascia to undergo necrosis and so reaches the surface. Accordingly, many abscess cavities resulting from deep-seated suppuration are of irregular shape, with pouches and loculi in various directions—an arrangement which interferes with their successful treatment by incision and drainage.

The relief of tension which follows the bursting of an abscess, the removal of irritation by the escape of pus, and the casting off of bacteria and toxins, allow the tissues once more to assert themselves, and a process of repair sets in. The walls of the abscess fall in; granulation tissue grows into the space and gradually fills it; and later this is replaced by cicatricial tissue. As a result of the subsequent contraction of the cicatricial tissue, the scar is usually depressed below the level of the surrounding skin surface.

If an abscess is prevented from healing—for example, by the presence of a foreign body or a piece of necrosed bone—a sinus results, and from it pus escapes until the foreign body is removed.

Clinical Features of an Acute Circumscribed Abscess.—In the initial stages the usual symptoms of inflammation are present. Increased elevation of temperature, with or without a rigor, progressive leucocytosis, and sweating, mark the transition between inflammation and suppuration. An increasing leucocytosis is evidence that a suppurative process is spreading.