Pelvic actinomycosis

A 47-year-old woman presented with a two-month history of left iliac fossa and flank pain with constipation and urinary frequency. A mass was discovered on bimanual palpation which was fixed to the pelvic sidewall.

Laboratory tests revealed mild neutrophilia, thrombocytosis and CA 125 was raised at 114iu/ml (normal range <35)

CT demonstrated a 7 cm left adnexal mass with peritoneal stranding and thickening of the adjacent rectosigmoid colon. Left sided hydronephrosis was caused by compression of the left ureter by the mass. An intrauterine device was present in the uterus.

MRI showed a complex left adnexal mass which encompassed the left ovary and involved the rectosigmoid colon and left ureter. The uterus, cervix and right ovary were normal and there were no enlarged pelvic lymph nodes.

Core biopsies of the mass were inconclusive. The patient underwent surgical resection of the adnexal mass and affected bowel. Histology confirmed actinomycosis of the left ovary with chronic inflammation of the ovary, salpinx and rectosigmoid colon. The patient was subsequently managed with high dose antibiotic therapy.

Actinomycosis is an uncommon chronic granulomatous disease caused by gram positive anaerobic bacilli from the Actinomyces genus of which Actinomyces isrealii is the most commonly isolated species. These opportunistic pathogens normally colonise the oropharynx, bowel and female genital tract, causing infection when they breach the mucous membranes. Infections are anatomically classified as either cervicofacial, thoracic or abdominogenital.

Female genital actinomycosis accounts for 3% of all cases [1] and occurs secondary to surgery, trauma, bowel perforation or foreign bodies [2]. The relationship between actinomycosis and intrauterine devices (IUDs) is well-documented. A. israelii infects up to 11.6% of IUDs with the risk of infection increasing with duration of use and up to 80% of female genital tract cases are attributable to the use of IUDs [3].

Pelvic disease is usually manifests as endometritis, salpingo-oophoritis or tubo-ovarian abscess [1]. Symptoms include lower abdominal pain, fever, offensive vaginal discharge, weight loss and nausea. Complications of advanced disease such as ureteric obstruction can cause hydronephrosis and flank pain, and colorectal strictures present as altered bowel habit or tenesmus.

Laboratory tests may indicate raised inflammatory markers, erythrocyte sedimentation rate and anaemia [4]. Raised CA 125 levels have also been observed [4]. Cultures are usually low yield and biopsies often inconclusive, making it difficult to differentiate from other causes of a pelvic mass and obtain a definitive diagnosis.

Imaging can point to a diagnosis of pelvic actinomycosis. Ultrasound is often the first-line imaging investigation; however the extent of disease is best depicted on MRI, which also allows for the characterisation of adnexal masses [5]. Tubo-ovarian abscesses are demonstrated as mixed T2 signal part-cystic masses and transfascial invasion of adjacent structures such as the rectosigmoid colon or ureters. This is seen more commonly with actinomycosis than with other abscess types [6]. Differentiation from ovarian carcinoma is difficult and may be aided by the presence of avid enhancement and ureteric obstruction, which is rare in primary malignancy.

Diagnosis is usually made at microbiology or histologically on surgical specimens [3]. Treatment typically consists of high-dose antibiotic therapy together with surgical or interventional management of any complications such as bowel strictures and hydronephrosis [2].

In summary, pelvic actinomycosis can be a challenging clinical diagnosis. When an adnexal/pelvic mass is discovered in a female patient, actinomycosis should be considered in the differential diagnosis, particularly when an IUD has been used and/or there are aggressive imaging features in the absence of conclusive biopsy results.