Isolated Abdominal Wall Actinomycosis after Hysterectomy

A forty-five-year-old female presented to her gynecologist with an abdominal wall mass in the supraumbilical region, five months after undergoing subtotal hysterectomy. After a further six months, due to an increase in the size of the mass and worsening symptoms, the patient was referred to our teaching hospital, where she was evaluated. A mass with discharging sinus was noted in the abdominal wall around the umbilicus. It was palpated to reveal an irregular, fixed, firm mass of 6 cm×5 cm, fixed to skin, but apparently free from underlying structures. The patient was afebrile and complained of occasional vomiting and constipation. The erythrocyte sedimentation rate (ESR) was elevated with 64 mm/h and the hemoglobin was 8.2 g/dL with moderate leucocytosis. Fine-needle aspiration cytology of the swelling showed clumps of filamentous bacteria suggestive of actinomycosis. Ultrasonography showed an irregular mass measuring 6.7 cm×5.4 cm within the anterior abdominal wall in the supraumbilical region. Another mass with the same features was present at the anterior abdominal wall of the pelvic region. Computed tomography (CT) of the abdomen showed an irregular density measuring 6 cm×5 cm projecting from the abdominal wall (Fig. 1), with dense inhomogeneous enhancement of solid components on injection of contrast (Fig. 2). These findings were consistent with the diagnosis of actinomycosis.

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FIG. 1.

Computed tomography scan showing abdominal wall mass.

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FIG. 2.

Contrast computed tomography scan shows enhanced solid contents in inhomogeneous mass.

Considering the size of the mass and an earlier poor response to empiric antibiotics, surgical intervention was decided upon. Pre-operatively, the patient was administered penicillin—500,000 IU/6 h and Dapsone—50 mg OD for four weeks. Laparotomy was done and three separate masses were excised. The final histopathology specimen showed “sulfur granules” consistent with Actinomyces (Fig. 3). Post-operatively, the patient was administered ceftriaxone-tazobactam for one week followed by oral amoxicillin for two weeks. The patient had an uneventful recovery.

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FIG. 3.

Histopathologic specimen showing target-like sulfur granule surrounded by inflammatory cells, suggesting actinomycosis.

Abdominal actinomycosis presents as an indolent chronic suppurative process with atypical symptoms that are often misinterpreted as malignant disease; the correct diagnosis is usually achieved only at operation [1]. Isolated abdominal wall actinomycosis is rare; by 2008, only 22 cases have been reported in the literature [2]. Whereas some cases have been reported after insertion of an intra-uterine device (IUD), this is the first reported case of isolated abdominal wall actinomycosis following hysterectomy. The pathogenesis of abdominal actinomycosis is not well understood, but it seems to require injury to the normal mucosa to penetrate and cause disease [3]. Once the bacteria invade tissue, a granulomatous inflammatory response ensues, leading eventually to necrosis and reactive fibrosis. Histologically, “sulfur granules” are characteristic [4]. Actinomycosis should be included in the differential diagnosis when a CT scan shows an infiltrative mass with unusual aggressiveness and dense inhomogeneous contrast enhancement, especially in patients with leukocytosis, fever, long-term use of an IUD [5], or hysterectomy.