Soft-tissue images. Abdominal actinomycosis

C.K. Leow

A 74-year-old woman, with no surgical history, presented with a 1-week history of constipation and pain in the left upper abdominal quadrant. On physical examination she had no pyrexia, but a slightly tender mass, measuring 5 cm in dimension, was palpable in the left upper quadrant. Apart from an elevated leukocyte count (12.4 × 10⁹/L with 70% neutrophils), the results of all other laboratory investigations were normal. Abdominal computed tomography revealed a mildly enhancing mass in the region of the splenic flexure (Fig. 1) with local involvement of the abdominal wall, which was thickened. At laparotomy, an inflammatory mass, involving part of the omentum, splenic flexure and anterior abdominal wall was resected en bloc and a primary colonic anastomosis performed. Despite continued intravenous antibiotic treatment with cefuroxime, ampicillin and metronidazole, the wound became erythematous and moist on postoperative day 4. The following day, the results of histologic examination of the operative specimen were available. The slides revealed multiple abscesses and actinomycetomas (Figs. 2 to ⇓4) but no evidence of a malignant mass. Penicillin (6 MU/6h) intravenously was begun. The low-grade pyrexia subsided over the next 24 hours, and the erythema around the wound and the weeping from it disappeared over 48 hours. At follow-up 12 months after the initial presentation, the woman was well.

FIG. 1

Computed tomography scan of the abdomen, demonstrating the enhancing mass (arrow) involving the anterior abdominal wall.

FIG. 2

Actinomycetoma (m) surrounded by inflammatory tissue on the serosa of the colon (hematoxylin–eosin, original magnification × 400).

FIG. 3

High magnification of the actinomycetoma (m) with numerous neutrophils crowning the mycetoma (hematoxylin–eosin, original magnification × 400).

FIG. 4

Methenamine silver stain of the actinomycetoma (m), demonstrating the typical filamentous hyphae (original magnification × 400).

Actinomyces, a filamentous gram-positive facultative anaerobic bacterium, is found in the normal flora of the oropharynx and gastrointestinal tract. Actinomycosis occurs as an opportunistic infection characterized by chronic inflammation, induration and the formation of abscesses, fistulae and sinuses with multiple draining sites.

Footnotes

Section editors: David P. Girvan, MD, and Nis Schmidt, MD
Submissions to Surgical Images, soft-tissue section, should be sent to Dr. David P. Girvan, Victoria Hospital Corporation, PO Box 5375, Station B, London ON N6A 5A5 or to Dr. Nis Schmidt, Department of Surgery, St. Paul’s Hospital, 1081 Burrard St., Vancouver BC V6Z 1Y6.