To investigate the magnetic resonance imaging (MRI) features of bilateral iliopsoas bursa expansion.

From December 2014 to May 2018, 13 cases of bilateral iliopsoas bursa expansion diagnosed by MRI in People′s Hospital of Fengxian were enrolled.

A total of 75 cases of iliopsoas capsular dilatation were diagnosed by MRI, and only 13 cases were bilaterally affected. Among the 13 cases, 10 cases were femoral head necrosis (bilateral in 6 cases, unilateral in 4 cases), 2 cases had hip trauma history, and 1 case was accidentally found during pelvic MRI. The incidence of bilateral involvement was 17.3% (13/75), with 37 cystic lesions, including unilocular lesion on each side in 5 cases, biatrial cystic lesions on each side in 3 cases, biatrial cystic lesions on the right and one cystic lesion on the left in 3 cases, unilocular cystic lesion on the right and biatrial cystic lesions on the left in 2 cases. The lesions displayed homogeneous water signal in 21 lesions and unhomogeneous signal in 16 lesions, and 7 lesions had separation inside. The lesions were round, oval or teardrop shaped and the size of the lesions range from 5 mm×3 mm×8 mm to 27 mm×23 mm×51 mm.The lesions located in front of the hip joint capsules, and internal-external-posterior or medial to iliopsoas muscle (tendon), 22 antra cysts communicated with the joint cavity. MRI also better showed femoral head necrosis in 10 cases, acetabular contusion and muscle contusion in 2 cases and femoral neck herniation fossa in 1 case.

MRI can clearly show bilateral iliopsoas bursa dilatation which locates in a specific anatomical site and has a characteristic feature of MRI signal, and can be used for etiological diagnosis.