Imaging description

The iliopsoas (also termed the iliopectineal, iliofemoral, iliac, or subpsoas) bursa is the largest normal bursa in the body, and is present in 98% of adults [1]. The iliopsoas bursa is located between the iliopsoas tendon and the anterior aspect of the hip joint, and serves to reduce tendon friction over the hip joint [2]. The bursa is lined by synovium and is normally collapsed. When distended with fluid, due either to effusive hip disease or primary inflammation of the bursal lining, the bursa becomes enlarged and appears as a fluid-filled structure in the groin at ultrasound, CT, or MRI (Figures 95.1–95.4) [1–3]. When the bursa is distended, communication with the hip joint is visible at US and CT in about 50% of cases, but is seen in virtually all cases at MRI [3]. Typically, the mass lies adjacent to the psoas muscle at the level of the hip joint, with variable proximal (into the pelvic retroperitoneum) and distal (into the upper portion of the thigh) extension [1,4, 5].

Importance

A distended iliopsoas bursa may be mistaken for a cystic neoplasm in the groin or pelvis.

Typical clinical scenario

A distended iliopsoas bursa may be detected incidentally as an asymptomatic mass or cause symptoms due to compression of adjacent structures such as lower extremity edema or femoral neuropathy [6–11].

Differential diagnosis

The location and fluid-filled appearance of a distended iliopsoas bursa are relatively distinctive. In problematic cases, MRI may help make the diagnosis by demonstrating communication with the hip joint.