Abdominal Actinomycosis

Actinomycosis of the abdomen is most often caused by a gram-positive anaerobic bacterium, Actinomyces israelii. However, many other species can cause the same syndrome. Actinomyces as commensals colonize the oral cavity, upper gastrointestinal tract, and female urogenital tract. Abdominal and genital actinomycosis is increasing in incidence with the use of intrauterine device (IUD). There are three major types of clinical infection syndromes in humans: cervicofacial (15%–60%), thoracic (15%–30%), and abdominal (20% including liver abscess). Rarely, the central nervous system may be involved. The intraabdominal actinomycosis presents with a vague symptomatology mimicking abdominopelvic neoplasia, clinically as well as radiologically. The intraabdominal form often occurs without any detectable cause but rarely may occur after gastrointestinal surgical procedures, endoscopic procedures, or trauma. Actinomycosis is an indolent, slowly progressive disease, and hence the diagnosis may be delayed by months to years.

The most common site in the gastrointestinal tract is in the ileocecal valve area, but any part may be involved. Mucosal involvements being rare, endoscopic procedures are not helpful in the diagnosis, and lymph nodes are seldom involved. It is assumed that once the disease is present in the abdominal cavity, drainage into the liver is the cause of liver abscess. Fortunately, when the disease manifests, it usually is in only one organ and is not disseminated. When infection occurs, other organs may be involved in the abscess formation.

Actinomyces is a part of the indigenous flora. Infections develop when the patient is in a susceptible state, such as during surgery, trauma, debilitating disease (e.g., malignancy, diabetes mellitus), or chronic corticosteroid therapy.