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A previously healthy 21 year old man presented with a two day history of worsening right lower quadrant abdominal pain. On examination he was found to have a fever (39°C) and his pulse rate was 110 beats/minute. There was tenderness with muscle guarding in the right lower quadrant, which worsened after a period of observation. Basic haematology and biochemistry tests were normal. Plain x rays of the chest and abdomen were also normal.
A diagnosis of acute appendicitis was made and the patient was transferred for emergency appendicectomy. The appendix proved to be macroscopically normal but a hard and fairly mobile mass was discovered in the right upper quadrant. We decided to extend the original Lantz incision transversely to improve access. The mass was arising from the right side of the greater omentum. It was loosely adherent to the proximal third of the transverse colon and the overlying peritoneum. The other viscera were normal. The mass was freed and excised with a 1 cm margin of macroscopically unaffected omentum. It was round in shape, 7 cm in diameter, and light brown in colour with an uneven surface.
Histological examination using haematoxylin and eosin staining confirmed that the specimen was a non-caseating granulomatous mass featuring eosinophilic granules. A Gram stained smear prepared from the lesion revealed sulfur granules characteristic of actinomycosis, made up of colonies of Gram positive actinomycetes. Therefore, the mass was an omental actinomycoma.
The patient made an uneventful postoperative recovery. We treated him with intravenous crystalline penicillin, 4MU six hourly for two weeks. Before discharge we investigated the patient’s gastrointestinal tract with a barium meal with follow through examination to rule out the possibility of an underlying predisposing condition, such as inflammatory bowel disease or an intraluminal lesion. He was discharged on oral amoxicillin, 500 mg eight hourly for a total of four months. We reviewed him six and then 12 months after surgery. On both occasions his white blood cell count, erythrocyte sedimentation rate, C reactive protein, and computed tomography scan of the abdomen and pelvis were completely normal.
Abdominal actinomycosis is an unusual condition, which tends to be a disease of insidious onset and vague symptoms.1 Recognised causal associations include a history of appendicitis,2 diverticulitis,3 inflammatory bowel disease, intrauterine contraceptive device use,4 or open and endoscopic surgery. However, we found no such association in our patient. Preoperative diagnosis is difficult and requires a high index of suspicion. When actinomycosis is suspected, computed tomography guided aspiration, with or without core biopsy of suspicious lesions, is a useful investigation.5 This may reduce the number of patients undergoing radical surgery for this benign disease. The role of surgery should be limited to cautious resection of the lesions with delivery of suitable specimens for histology and microbiology.
The organisms tend to be sensitive to cephalosporins, tetracyclines, and macrolides. The duration of treatment is a controversial issue, but long courses are recommended.1 The prognosis for patients suffering from abdominal actinomycosis is good provided that adequate antibiotic cover is instituted at an early stage.