2378 Hepatic Actinomycosis Masquerading as Gastrointestinal Malignancy

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INTRODUCTION: Abdominal actinomycosis is a rare cause of liver cysts and rectal masses. It remains a diagnostic challenge. CASE DESCRIPTION/METHODS: A 60 year-old male (patient L) presented with a rectal mass found on colonoscopy. Biopsies were inconclusive; however, staging CT demonstrated liver lesions presumed to be metastases from rectal carcinoma. The patient began to have recurrent fevers, night sweats, and unintended weight loss, prompting an extensive infectious work-up notable only for a positive quantiferon. In the interim, patient L underwent laparoscopy and liver biopsy to further evaluate his presumed malignancy. Frozen sections revealed caseating granulomas with negative AFB and stains. The patient was diagnosed with GI tuberculosis (TB) based on constitutional symptoms, positive quantiferon, and frozen section findings, and was started on standard four-drug therapy. Final pathology resulted in visualization of sulfur granules, diagnostic of actinomycosis. TB treatment was discontinued and augmentin was started for a 6 month course. DISCUSSION: Actinomyces colonizes the oropharynx and digestive and genital tracts. It infrequently causes disease. Abdominal infection accounts for 20% of actinomycoses; of these, only 15% report liver involvement. Infection is associated with compromise of the mucosal barrier, either due to instrumentation or appendicitis. Our patient had recently undergone colonoscopies to diagnose his rectal mass. As in Patient L, actinomycotic liver abscesses usually present with an indolent course; symptoms include insidious abdominal pain, fever, and weight loss. Although these symptoms may be associated with malignancy, fever even in cancer patients should be presumed infectious until proven otherwise. Imaging commonly shows loculated cysts in contrast to patient L’s simple cysts with no loculations. The signs, symptoms, and radiographic findings of abdominal actinomycosis are non-specific and indistinguishable from colorectal cancer, inflammatory bowel disease, and gastrointestinal TB, making diagnosis difficult. In one review, laparotomy was considered essential for diagnosis in 69% of cases; pre-operative diagnosis rate was less than 10%. Treatment generally involves 6-12 months of beta-lactams. In summary, GI actinomycosis poses a diagnostic challenge as it is a rare clinical entity with nonspecific symptoms and endoscopic and radiographic findings. Successful diagnosis often requires a collaborative, multi-disciplinary approach. Treatment is with prolonged antibiotics.

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