Primary iliopsoas abscess due to Staphylococcus aureus bacteremia

A 17-year-old girl with poorly controlled type I diabetes mellitus presented with a 2-week history of fever and limping. She reported no history of previous trauma. On examination, there was reduced range of motion in the right hip and a positive psoas sign. The cardiovascular and lung examinations were unremarkable. Blood investigations showed leukocytosis (25 x 10³/uL). The chest radiograph and transthoracic echocardiography findings were normal. Because psoas abscess was suspected, CT of the abdomen and pelvis was performed, which revealed multiloculated rim-enhancing collection at the right iliopsoas muscle (Figure 1). She then underwent percutaneous drainage in which a copious amount of purulent material was drained. The blood culture revealed Staphylococcus aureus (sensitive to oxacillin and trimethoprim-sulfamethoxazole). In the ward, she was treated with intravenous cloxacillin 2 g every 4 hours for 2 weeks. One week later, the musculoskeletal ultrasonography showed a reduction in the size of the abscess. Her fever subsided, and the right hip pain started improving. Subsequently, she took oral trimethoprim-sulfamethoxazole for another 4 weeks, which had resulted in ultrasonographic resolution of the right iliopsoas abscess.

FIGURE 1: Computed tomography (CT) of the abdomen and pelvis shows multiloculated rim-enhancing collections at the right iliopsoas muscle.

Iliopsoas abscess can be classified as a primary or secondary abscess. The former occurs as a result of hematogenous spread of an infectious process from an occult source, while the latter occurs when there is a direct spread of infection from an adjacent structure ¹ . The presenting features of iliopsoas abscess were non-specific, and the classic Mynter’s triad of fever, pain, and limping is present in 30% of the patients ^{1 , 2} . S. aureus and Escherichia coli are the most common causative organisms of primary and secondary iliopsoas abscesses, respectively ³ . Treatment of iliopsoas abscess involves the use of appropriate antibiotics along with abscess drainage ¹ . Iliopsoas abscess is a rare but serious complication of S. aureus bacteremia and should be suspected in patients presenting with fever and limping. Early diagnosis and prompt treatment are crucial to a successful outcome.