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

by Alexis Thomson; Alexander Miles

The caseation of tuberculous granulation tissue and its liquefaction is a slow and insidious process, and is unattended with the classical signs of inflammation—hence the terms “cold” and “chronic” applied to the tuberculous abscess.

In a cold abscess, such as that which results from tuberculous disease of the vertebræ, the clinical appearances are those of a soft, fluid swelling without heat, redness, pain, or fever. When toxic symptoms are present, they are usually due to a mixed infection.

A tuberculous abscess results from the disintegration and liquefaction of tuberculous granulation tissue which has undergone caseation. Fluid and cells from the adjacent blood vessels exude into the cavity, and lead to variations in the character of its contents. In some cases the contents consist of a clear amber-coloured fluid, in which are suspended fragments of caseated tissue; in others, of a white material like cream-cheese. From the addition of a sufficient number of leucocytes, the contents may resemble the pus of an ordinary abscess.

The wall of the abscess is lined with tuberculous granulation tissue, the inner layers of which are undergoing caseation and disintegration, and present a shreddy appearance; the outer layers consist of tuberculous tissue which has not yet undergone caseation. The abscess tends to increase in size by progressive liquefaction of the inner layers, caseation of the outer layers, and the further invasion of the surrounding tissues by tubercle bacilli. In this way a tuberculous abscess is capable of indefinite extension and increase in size until it reaches a free surface and ruptures externally. The direction in which it spreads is influenced by the anatomical arrangement of the tissues, and possibly to some extent by gravity, and the abscess may reach the surface at a considerable distance from its seat of origin. The best illustration of this is seen in the psoas abscess, which may originate in the dorsal vertebræ, extend downwards within the sheath of the psoas muscle, and finally appear in the thigh.

Clinical Features.—The insidious development of the tuberculous abscess is one of its characteristic features. The swelling may attain a considerable size without the patient being aware of its existence, and, as a matter of fact, it is often discovered accidentally. The absence of toxæmia is to be associated with the incapacity of the wall of the abscess to permit of absorption; this is shown also by the fact that when even a large quantity of iodoform is inserted into the cavity of the abscess, there are no symptoms of poisoning. The abscess varies in size from a small cherry to a cavity containing several pints of pus. Its shape also varies; it is usually that of a flattened sphere, but it may present pockets or burrows running in various directions. Sometimes it is hour-glass or dumb-bell shaped, as is well illustrated in the region of the groin in disease of the spine or pelvis, where there may be a large sac occupying the venter ilii, and a smaller one in the thigh, the two communicating by a narrow channel under Poupart's ligament. By pressing with the fingers the pus may be displaced from one compartment to the other. The usual course of events is that the abscess progresses slowly, and finally reaches a free surface—generally the skin. As it does so there may be some pain, redness, and local elevation of temperature. Fluctuation becomes evident and superficial, and the skin becomes livid and finally gives way. If the case is left to nature, the discharge of pus continues, and the track opening on the skin remains as a sinus. The persistence of suppuration is due to the presence in the wall of the abscess and of the sinus, of tuberculous granulation tissue, which, so long as it remains, continues to furnish discharge, and so prevents healing. Sooner or later pyogenic organisms gain access to the sinus, and through it to the wall of the abscess. They tend further to depress the resisting power of the tissues, and thereby aggravate and perpetuate the tuberculous disease. This superadded infection with pyogenic organisms exposes the patient to the further risks of septic intoxication, especially in the form of hectic fever and septicæmia, and increases the liability to general tuberculosis, and to waxy degeneration of the internal organs. The mixed infection is chiefly responsible for the pyrexia, sweating, and emaciation which the laity associate with consumptive disease. A tuberculous abscess may in one or other of these ways be a cause of death.

Residual abscess is the name given to an abscess that makes its appearance months, or even years, after the apparent cure of tuberculous disease—as, for example, in the hip-joint or spine. It is called residual because it has its origin in the remains of the original disease.

Fig. 34.—Tuberculous Abscess in right lumbar region in a woman aged thirty.

Diagnosis.—A cold abscess is to be diagnosed from a syphilitic gumma, a cyst, and from lipoma and other soft tumours. The differential diagnosis of these affections will be considered later; it is often made easier by recognising the presence of a lesion that is likely to cause a cold abscess, such as tuberculous disease of the spine or of the sacro-iliac joint. When it is about to burst externally, it may be difficult to distinguish a tuberculous abscess from one due to infection with pyogenic organisms. Even when the abscess is opened, the appearances of the pus may not supply the desired information, and it may be necessary to submit it to bacteriological examination. When the pus is found to be sterile, it is usually safe to assume that the condition is tuberculous, as in other forms of suppuration the causative organisms can usually be recognised. Experimental inoculation will establish a definite diagnosis, but it implies a delay of two to three weeks.