Fusobacterium Liver Abscess
A 65-year-old man presented to the emergency department with fever, chills, nausea and abdominal pain. A week prior to this admission the patient had been worked up for hematuria, a computed tomography (CT) scan of the abdomen showing multiple rim-enhancing liver lesions. The differential diagnosis at that time included metastatic colon carcinoma, amebic abscess and bacterial abscess seeded from sigmoid diverticulitis. Five days prior to admission, the patient underwent colonoscopy with biopsies, which showed acute inflammation but no evidence of malignancy. On the day of admission, repeat CT scan showed interval increase in size of his rim-enhancing liver lesions (fig. ) as well as acute cecal diverticulitis, chronic pancreatitis and a large thrombus in the portal vein. Based on the interval increase in size of the liver lesions and the colonoscopy findings, an infectious etiology was favored and four drains were placed for presumed abscesses (confirmed with drainage of purulent fluid) and empiric treatment with ciprofloxacin and metronidazole was initiated. The patient was also started on heparin for his portal vein thrombosis 3 days after admission (transitioned to Lovenox twice daily 6 days after admission). On day four, the causative organism for the patient's abscesses remained unidentified and a liver biopsy was performed to re-evaluate for the possibility of neoplasia or an unusual organism.\nThe liver biopsy showed neutrophil-rich debris (fig. ), consistent with abscess, and liver parenchyma embedded in fibrous tissue and scattered mixed inflammation consistent with abscess wall; no peliosis or viropathic changes were appreciated. Immunohistochemical staining for CD34 and CD31 showed no evidence of a vascular neoplasm, and S100 was negative, arguing against a neural crest-derived tumor (not shown). No bacteria were identified on Gram stain (fig. ), and no fungal organisms were seen on periodic acid-Schiff diastase or Gomori methenamine-silver stains. Also, there were no mycobacterial organisms on an acid-fast bacilli-stained slide (not shown). Warthin-Starry (WS) stain, however, showed filamentous bacteria within the necrotic debris (fig. ) consistent with Fusobacterium infection []. A week after admission, detection of Fusobacterium sp. in cultures of the patient's hepatic abscess fluid confirmed the diagnosis of Fusobacterium liver abscess.\nIn the interval between the biopsy and identification of the causative organism, ciprofloxacin was empirically changed to ceftriaxone because of concern for Streptococcus milleri infection; the patient improved on the combination of ceftriaxone 1 g daily and metronidazole 500 mg three times daily, his drains were removed, and he was discharged 8 days after admission on antibiotics as described above.