Abdominopelvic actinomycosis: spectrum of imaging findings and common mimickers

Abstract

Background: Actinomycosis is a rare suppurative disease that may mimic other inflammatory conditions on imaging. Its invasive nature may lead to mass formation and atypical presentation thus making accurate diagnosis quite difficult.

Purpose: To describe the different aspects of abdominopelvic actinomycosis on cross-sectional imaging and indicate discriminative findings from other inflammatory or neoplastic diseases.

Material and methods: In our study we analyzed 18 patients (15 women, 3 men; age range, 25-75 years; mean age, 50 years) with pathologically proved abdominopelvic actinomycosis. Contrast-enhanced abdominal computed tomography (CT) had been performed in all patients. Eleven patients had a history of using intrauterine contraceptive devices. Bowel site, wall thickness and enhancement degree, inflammatory infiltration, and features of peritoneal or pelvic mass were evaluated at CT.

Results: The sigmoid colon was most commonly involved. Most patients showed concentric bowel wall-thickening, enhancing homogenously and inflammatory infiltration of pericolonic fat was mostly diffuse. In 11 patients, one or more pelvic abscesses were revealed, while a peritoneal or pelvic mass adjacent to the involved bowel segment was seen in three cases. Infiltration into the abdominal wall was seen in three cases while in one case there was thoracic dissemination.

Conclusion: Actinomycosis is related not only to long-term use of intrauterine contraceptive devices and should be included in the differential diagnosis when cross-sectional imaging studies show concentric bowel wall-thickening, intense contrast enhancement, regional pelvic or peritoneal masses, and extensive inflammatory fat infiltration with abscess formation.

Keywords: Pelvis; abscess; actinomycosis; computed tomography (CT).

Fig. 1.

(a) Contrast-enhanced CT axial image and (b) contrast-enhanced CT coronal image: many “cystic” lesions consistent with abscesses are seen in the pelvic area, in a woman wearing IUD.

Fig. 2.

An inflammatory mass involving the right adnexa and the sigmoid region is seen on this CT image. There is also extensive inflammatory infiltration of the pelvic fat while some loops of small bowel are also involved.

Fig. 3.

(a, b) Many collections and abscesses are found in the pelvis and there is also inflammatory involvement of the fat and mild small bowel wall-thickening very well seen on these CT images.

Fig. 4.

(a, b) Abdominal CT images: bowel compression is evident, thickening of the sigmoid colonic wall and an amount of free fluid in the pelvis. There is also extensive inflammatory infiltration of the left lateral abdominal wall.

Fig. 5.

CT image shows a very large abscess of the left lateral abdominal wall.