Abdominal Actinomycosis Complicated by Delayed Splenic Abscess

A 50-year old female presented with one month of low abdominal pain with a palpable mass. The patient had no previous history of abdominal operation or trauma. Physical examination revealed a palpable, tender, ill-defined mass of the lower abdomen. The patient had an intrauterine device (IUD) that had been placed two years previously. Laboratory findings, including tumor markers, were all within normal ranges. Computed tomography (CT) scan revealed an ill-defined, enhancing lesion with central low densities in the right side of the pelvic cavity, which had an impending fistulous connection with the right inguinal area (Fig. 1A). A small bowel neoplasm was suspected clinically, so the patient underwent exploratory laparotomy. Laparotomy revealed that the distal ileum was inflamed and intermingled, adherent to the anterior abdominal wall and urinary bladder. Ileocecectomy was performed for pathologic examination, which failed to make a specific diagnosis, and the patient was discharged. Three months later, the patient presented with a fever above 39°C, hypotension (systolic pressure near 80 mm Hg), and left upper quadrant abdominal pain. Laboratory investigation revealed WBC 15,600/mm³, with 87% neutrophils, and C-reactive protein 29.8 mg/dL. A CT scan revealed irregular shaped, multiloculated cystic lesions in the spleen and a perilesional hypodensity suggestive of splenic abscess (Fig. 1B). The patient was diagnosed with splenic abscess-associated septic shock, and emergent splenectomy was performed (Fig. 2). Pathologic examination revealed sulfur granules in the splenic tissue (Fig. 3), and retrospective review noted that sulfur granules were also present in the previous ileocecectomy specimen. Abdominal actinomycosis was diagnosed, and the patient underwent two weeks of intravenous, followed by three months of oral penicillin treatment. The IUD was removed immediately after the diagnosis. Currently, six months postoperatively, the patient is doing well without evidence of disease recurrence.

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FIG. 1.

(A) Computed tomography scan. Ill-defined enhancing lesion with internal low densities is observed. (B) Multiple, small cystic lesions and a perilesional low density are observed at the lower pole of the spleen.

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FIG. 2.

Surgical specimen. Multiple abscess cavities are noted on section.

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FIG. 3.

Sulfur granule (H&E, x200). Branched, filamentous bacteria in sulfur granules and surrounding inflammatory cells are observed in the abscess.

Abdominal actinomycosis poses a diagnostic challenge, and most cases undergo surgical intervention because of the suspicion of malignant disease, complicated inflammatory bowel disease, or abscess. Sung et al. reported 23 patients who underwent surgery before a definite diagnosis was made, and in all patients, actinomycosis was confirmed postoperatively [1]. In the series of Sung et al., only four cases (17%) were presumed to be actinomycosis before surgery, and the literature also shows that the diagnosis is made preoperatively in fewer than 10% of patients [1,2]. Because medical therapy alone or surgical drainage and antibiotic treatment is often curative [3], one should suspect actinomycosis in relevant clinical settings and diagnose it via the least invasive method to avoid unnecessary surgery. Splenic actinomycosis has been known to occur more often in immunocompromised patients, and the hematogenous seeding of actinomyces is believed to be a possible mechanism of microorganism inoculation to the spleen. By contrast, the lung and liver are two of the organs affected most commonly from hematogenous dissemination of actinomycosis in immunocompetent patients [4]. In this patient, although she was not immunocompromised, prolonged exposure to untreated abdominal actinomycosis might have facilitated blood stream infection and the resultant splenic abscess. However, we could not find any relevant explanation for splenic actinomycosis rather than lung or liver involvement. Timely diagnosis and prompt initiation of medical treatment would have prevented this late complication.

Surgery is a valuable tool for the definitive diagnosis and treatment of actinomycosis, and combined medical-surgical therapy has been advocated. However, an increasing body of literature supports the approach of attempting initial cure with medical therapy alone and reserving surgery for refractory cases [5]. All of the cases of splenic actinomycosis in the English literature (except one) were treated with splenectomy after failure of a short course of medical treatment. There have been debates on post-splenectomy therapeutic regimens, but a course of intravenous penicillin for two to six weeks followed by oral penicillin for 6–12 mos is accepted generally [5].