Gas Formation in Abdominal Abscesses: A Roentgen Study

Abstract

The early diagnosis of abdominal abscesses is of considerable clinical importance. Roentgenologic examination is not only valuable in their diagnosis and localization but also in the differentiation from tumors and hematomas. The roentgenologic features of abdominal abscesses have been described in a small number of excellent studies and will not be the subject of this discussion (1, 2, 3). Generally, the roentgenologic signs depend to a great extent upon the localization of the abscess. Thus, an intraperitoneal abscess may be demonstrable as a space-occupying process displacing the intestinal loops, which usually reveal some degree of ileus in the neighborhood of such an infection. A roentgenologic sign of prime importance is the obliteration of the intermuscular and subperitoneal fat layers of the adjacent abdominal wall, which may be attributed to edema associated with the inflammatory condition. Abscesses invading or originating in the retroperitoneal space may cause blurring or obliteration of the psoas shadows and frequently lead to swelling of the soft tissues of the flank, which may be demonstrated to advantage on roentgen examination. The changes in the position and motility of the diaphragm associated with subphrenic, intraperitoneal, and retroperitoneal abscesses are generally known. These signs, in conjunction with clinical findings, will in many instances be sufficient to establish a diagnosis. Not infrequently, however, the roentgenologic evidence mentioned above may be equivocal or difficult to demonstrate. In children and old people, the subperitoneal and intermuscular fat layers of the abdominal wall may be poorly defined, and marked intestinal distention may obscure the detail of the psoas shadows. On the other hand, large retroperitoneal tumors and hematomas may distort the structures of the abdominal wall and make their fat layers indistinct. Thus, there remain cases in which the differential diagnosis between an inflammatory mass and tumor or hematoma is difficult. Any additional roentgenologic sign, therefore, will be of definite value. It has been shown by Laurell (1, 2) that abscesses may occasionally contain gas vesicles visible roentgenologically. The roentgen demonstration of gas production in infections caused by Cl. welchii and related organisms is now generally recognized as a valuable diagnostic procedure (4). It is surprising, therefore, that in the roentgenologic literature little attention is given to gas formation in infections which are caused by other organisms, such as colon bacilli and anaerobic streptococci. Subphrenic abscess is the only condition in which gas formation, due to the colon bacillus, is commonly known to occur (5). There is no doubt, however, that in many subphrenic abscesses the observed gas represents air which has penetrated into the abscess cavity by way of a fistula from the lungs or gastro-intestinal tract.