[Abdominal actinomycosis. Report of 4 clinical cases studied with radiography].

We report 4 cases of pathologically proven abdominal actinomycosis. US and CT demonstrated an infiltrative abdominal mass with ill-defined margins and heterogeneous enhancement after IV contrast. The ileo-cecal region was involved in one case; the mass appeared following cholecystectomy and recurred 3 years after surgical resection in one case; and no predisposing factor was identified in the 2 other cases. In one of these, recurrence was observed 12 years after the first episode. Actinomycosis must be included in the differential diagnosis of invasive abdominal lesions with "malignant" appearance.