Intra-abdominal actinomycosis, the great mime: case report and literature review

Background: Actinomycosis is a rare, insidious, infectious disease. Cervicofacial, thoracic and abdominopelvic districts are most commonly involved. Its tendency to involve surrounding structures may mimic a tumor on imaging studies. Early diagnosis, obtained with mini-invasive methods or surgical biopsy, is fundamental to optimize therapeutic approach and to reduce morbidity due to aggressive surgery. Antibiotic therapy is the cornerstone of the treatment of actinomycosis, but the combination with a surgical resection can be necessary in patients who do not respond to medical treatment. Methods: A 66-years old female presented at our attention with an abdominal, retroperitoneal mass found during clinical tests for a vertiginous syndrome. Patient presented with asthenia, anorexia, weight loss, and sacral pain. A retroperitoneal mass, studied with Computed tomography (CT) and Positron emission tomography (PET), was found. No inflammatory signs were found in laboratory tests. Previous core biopsies did not provide the expected results. Cause of that, the patient was prepared for a surgical laparoscopic biopsy and ureteral stenting. After frozen biopsies, histological findings have identified filaments of Actinomyces. No apparent cause of this infection has been identified at first exploration. Results: The patient was treated with antibiotic therapy for three months (Amoxicillin: 1g three times daily). At three months first follow-up, the CT shows the reduction of the retroperitoneal mass and the presence of diverticulosis of the sigma near the mass, in absence of signs of fistulisation. Conclusion: Abdominopelvic actinomycosis should be considered in patients with unusual abdominal mass on abdominal CT or PET. Early diagnosis is necessary to avoid aggressive surgery and its morbidities. Open/laparoscopic surgical biopsy is often necessary to identify the infection. Antibiotic therapy is the standard treatment but surgery can help to optimize medical approach removing necrotic tissue and persistent sinuses.