Omental actinomycosis mimicking a foreign body infection.

Actinomycosis is a chronic suppurative granulomatous disease caused by Actinomyces species. Abdominal actinomycosis is a rare condition and difficult to diagnose before surgery. Here, we report a case of omental actinomycosis mimicking a foreign body infection on computed tomography (CT). A 47-year-old man presenting with abdominal pain had a heterogeneous area comprising a 2-cm long linear radiopaque material with surrounding enhancing soft tissue density lesions and fat infiltrates, measuring 9 × 8 cm in the omentum of the right upper quadrant on CT. We assumed that the linear radiopaque material was a foreign body, such as a fish bone. Laparoscopy-assisted right hemicolectomy and partial omentectomy were performed under radiological suspicion of foreign body infection. Histological examination revealed the omental lesion to be actinomycosis. The patient was treated with antibiotics for 10 weeks, and he recovered well without any complication. Omental actinomycosis mimicking a foreign body infection is rare. The experience and knowledge regarding the variable CT findings of abdominal actinomycosis are useful because it should be differentiated from malignancy and other inflammatory conditions.