Discussion
Psoas abscess is the collection of pus in the iliopsoas muscle compartment and usually occurs secondary to renal, intestinal, or skeletal infection. Primary infection leading to psoas abscess is relatively rare although, it occurs more frequently among children and young adults and tends to be more common in developing countries (2)
Primary psoas abscess is frequently a single microorganism complication, including Staphylococcus aureus, and Mycobacterium tuberculosis , and may also occur due to Brucella spondylodiscitis. Although CT scan is the modality of choice when a psoas abscess is suspected, in rare etiologies of psoas abscess like Brucellosis, MRI can provide more detailed data and is the method of choice in these circumstances (2).
In our case, according to the prevalence of Brucellosis in Iran as an endemic region, serology and MRI were sufficient, enabling us to make the final diagnosis.
Although abscess drainage regardless of the causative microorganism is the recommended treatment for the psoas abscess in many studies and guidelines and antibiotics alone are not considered curative unless the abscess is small (<3mm) (2), a study conducted by Tabrizan et al. revealed that using Antibiotics alone in iliopsoas abscess management has a success rate of 78% (5). It is also recommended by Yacob et al. in a study in 2009 that treatment of Psoas abscesses should be initiated with antibiotics and small abscesses should be treated with antibiotics alone (6).
In our case, the abscess was about 34*12*16mm, which was relatively small. This case highlights that small psoas abscesses could be treated successfully using oral antibiotics and no drainage.