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Case of the Week #244

7 June 2012 - Case of the Week #244

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Case of the Week #244

Clinical History:

An 11 year old girl with no prior medical history presented with abdominal pain, fever, general fatigue, night sweats and anemia. Computed tomography scan showed a 4 centimeter tumor in the right kidney extending into the liver, and multiple 1 to 2 millimeter lung nodules.

The clinical differential diagnosis included lymphoma, Wilm's tumor and an unknown primary with metastasis. A renal biopsy was obtained.

CT scan images:

Micro images:

What is your diagnosis?


Renal actinomycosis


The renal biopsy showed marked acute and chronic inflammation with occasional sulfur granules characteristic of Actinomyces species.

Actinomycosis is a chronic suppurative and granulomatous disease of the cervico-facial, thoracic or abdominal areas caused by the Actinomyces species. It is sometimes called the most "misdiagnosed disease", because abscesses can mimic malignancy, as in this case. As a result, these abscesses may cause unnecessary surgical resections.

Actinomyces are anaerobic gram-positive non-acid fast filamentous bacteria that are normal flora in the mouth and gastrointestinal tract. Actinomycosis is most frequently caused by Actinomyces israelii, part of the normal flora in the vagina, colon and mouth. Infection is established by a breach of the mucosal barrier during dental, GI or other procedures or due to diseases such as diverticulitis or appendicitis.

Actinomyces israelii is also the most common cause of disseminated actinomycosis. Disseminated disease is usually caused by perforation of the gastrointestinal tract, intrauterine devices, aspiration or poor oral hygiene.

This patient was successfully treated with antibiotics post-operatively and without complications. Although renal actinomycosis is rare, it should be included in the differential diagnosis for a renal mass.


1. Horino T, Yamamoto M, Morita M, Takao T, Yamamoto Y, Geshi T. Renal actinomycosis mimicking renal tumor: case report. South Med J 2004;97:316

2. Yegez JF, Martinez SA, Sands LR, Hellinger MD. Pelvic actinomycosis presenting as malignant large bowel obstruction a case report and review of the literature. Am Surg 2000 66:85

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