Under the term “abscess” is meant that which is described as acute abscess. Under certain circumstances, especially when they are produced by the facultative pyogenic organisms rather than the obligate, abscesses form more slowly, and may be spoken of as subacute. These are terms used in contradistinction to the so-called cold abscesses, which, although clinically bearing a certain resemblance to the acute, are in almost every pathological respect different from it. Cold abscesses will be considered under the head of Tuberculosis. It is possible to have an acute pyogenic infection of a cold abscess; in such case we have acute manifestations. Gravitation abscesses are those where pus forming in one part tends to migrate, usually in the direction in which gravity would take it, extending into portions deeper or lower. Perhaps the best illustration of this is the pointing of a psoas abscess below Poupart’s ligament. Metastatic abscesses are those which are formed as the result of embolic processes, each one being in miniature a repetition of a lesion which has occurred at some other part of the body. The underlying fact concerning metastatic abscesses is that the primary process has occurred in some other portion of the body, whence it has been distributed as above. These will be considered in the chapter treating of Pyemia.
The product of all acute suppurative lesions is pus. This is an opaque fluid of creamy consistence and whitish or grayish appearance, varying in density, met with in amounts from a minute drop to half a gallon or more. Under ordinary circumstances it is odorless, and its reaction, either acid or alkaline, is very faint. It is, like the blood, composed of a fluid and a solid portion. The solid portion consists of so-called pus corpuscles and other debris of tissue, which vary with the site of the disease and the parts involved. The source of the pus corpuscles has been cited and the statement made that they are in effect the bodies of phagocytes which have perished in the biochemical fight for existence of the parent organism. Cocci or bacilli are found in pus corpuscles and also in the surrounding fluid.
Pus should be without odor, but under certain circumstances it possesses an odor which will vary in character according to the source of the pus or the nature of its principal bacterial excitant. Pus from the upper end of the alimentary canal frequently has the sour smell of gastric contents; that from the neighborhood of the lower end, the fetid odor which is for the most part due to the action of the colon bacillus. Inasmuch as colon bacilli are found in widely distant parts of the body, they may also give an unpleasant odor to pus even from a brain abscess. When the pus has become contaminated with the ordinary saprophytic organisms, it may smell like any other decomposing material. The older writers called it ichorous pus, while sanious pus was supposed to be that more or less mixed with blood, undergoing ammoniacal decomposition or else strongly acid. Pus sometimes has a well-marked blue or bluish-green tint. This is due to the presence of the bacillus pyocyaneus, already described. An orange tint is sometimes given by the presence of hematoidin crystals, due to the original hemorrhagic character of the infected exudate. The former appearance indicates usually a slow course to the suppurative lesion, while the latter has been regarded by some as affording an unfavorable prognosis. Distinctly red pus, whose tint is due to the presence of a bacillus giving bright-red cultures on blood serum, has been noted in other instances. This can readily be distinguished from blood, because upon dressings it does not change color.
Pus may form superficially, when it is called subcutaneous suppuration, in which case there is a minimum of pain, because tension is not great and the distance to the surface is short. Collections which form beneath the fasciæ, especially the deeper fasciæ of the limbs and trunk, give rise to much more extensive disturbance, both locally and generally, and frequently do not point for many days; or, instead of pointing, burrow deeply and find their outlet at some undesirable point. These are known as subfascial collections. Subperiosteal abscesses give rise to still more pain, because of the unyielding character of their limiting structures, and the symptoms caused by them are acute and distressing.
An illustration of the pain which may follow deep suppuration may also be seen in the ordinary panaritium, or bone felon, where the path of infection is from without, but the destructive lesion is confined within absolutely unyielding tissues, at least at first. Along certain tissues infection spreads with rapidity. This is particularly true of the delicate areolar tissue seen between tendons and tendon sheaths, and the infectious process may follow this tissue wherever it shall lead, even along complex courses.
The question often arises, Can pus be resorbed? There is no question but that small amounts of pus are disposed of by phagocytic activity, and the disappearance of purulent infiltration, under the influence of favoring remedies, or even when let alone, is not infrequently noted. True pus resorption is a question of phagocytic possibilities, and can occur only in very limited degree, as a result upon which it is not safe to count, and which is capable of encouragement only up to a certain point.
One inevitable law seems to govern collections of pus, that when they advance or migrate in any direction it is in that of least resistance. This causes them to take peculiar and sometimes disastrous courses, but it is a law which is never violated. It leads to the bursting of abscesses into the brain, into the pleural cavity, into the peritoneal cavity, the bowel, and elsewhere; it leads to a condition where pus may travel along a path even a foot or more in length, rather than come to the surface, a distance of perhaps an inch, and affords one of the best reasons for early operative interference so that the disastrous effects of burrowing may be obviated. When the pus is limited to a drop or fraction thereof the abscess is called a furuncle, especially when in the skin. The average “boil” of the layman is a subcutaneous or subfascial abscess. When the infiltration is pronounced, and when there has been more or less extensive destruction of tissue, with perhaps formation of numerous outlets for the escape of pus and detritus, it is known as a carbuncle. (See [Chapter XXVI].) In certain conditions small superficial furuncles or boils form, sometimes in great number and almost synchronously, or, as it were, in crops. This condition is known as general furunculosis.
Signs and Symptoms of Abscesses.
—The appearances by which pus may be suspected or detected are those of congestion and hyperemia, more or less abruptly circumscribed and markedly accentuated. Along with these there is more or less edema or edematous infiltration of the skin and overlying tissue, which permits of that peculiar appearance known as “pitting on pressure.” Often, too, there is a distinctly edematous swelling of the parts, especially around the margin, with brawny infiltration of the centre of the infected area. Numerous vesicles occasionally are noted upon the skin, which may be filled with reddish serum. When softening and pus formation occur, there is a condition which to the palpating fingers gives the characteristic sensation known as fluctuation. Fluctuation simply points out the presence of fluid beneath; but when in an area marked as thus described fluctuation is noted, it means the presence of pus. It is detected by manipulating in a direction parallel to and concentric with the axis of the limb or part. The pain is also in most instances significant; patients speak of it as having an intense and throbbing character. With these local signs occur symptoms indicating some degree of septic intoxication, i. e., pyrexia, chills, malaise, sweats, etc., which are corroborative indications, their intensity being a reasonably correct index of the severity and gravity of the local infection.
When a deep-seated abscess is suspected a careful blood count will often permit a diagnosis to be made. This is conspicuously true of cases of appendicitis. If leukocytosis is established there should be immediate operation. (See [Chapter II].)