CT and MRI diagnosis of enlarged iliopsoas bursa

Objective: To study the manifestations and diagnostic value of CT and MRI on enlarged iliopsoas bursa. Methods: CT and MRI films of 23 patients with enlarged iliopsoas bursa were studied retrospectively. All these patients were positively diagnosed by aspiration of synovial fluid or surgical operation. Results: Enlarged iliopsoas bursas in all the 23 cases appeared at the level of or part of the acetabulum sections in only one side, ranging from 2.0 cm to 6.5 cm. The area (transverse diameter x vertical diameter) at the largest section was from 1.0 cm x 1.0 cm to 2.8 cm x 3.8 cm. All of them appeared as round, oval or upside-down water drop-like cyst and located posterolateral to external iliac blood vessels and or femoral blood vessels, medial to iliopsoas muscle (tendon), and anterior to hip joint capsule. In 16 cases, external iliac blood vessels and or femoral blood vessels were pushed forward and or inward. In 10 cases, there was an arched compression corresponding to the bursa in the medial edge of the iliopsoas muscle. In 15 cases, the bursas were surrounded or covered by muscle bundles, which became thinner and thinner downwards and disappeared at last. The bursas in 3 cases extended upwards along the acetabulum and internal surface of the ilium base, protruding into iliopsoas muscle. In 8 cases, the bursas went downwards and located anterolaterally to pectineal muscle, 5 of which presenting as an upside-down water drop. On CT films all 23 cases showed hypodense lesions with CT value from 12 to 46 HU. In 11 cases, the thin cystic wall was demonstrated, while in the other 12 cases, it was difficult to identify the cystic wall. In 5 out of 7 cases with contrast enhanced CT, the cystic wall demonstrated a little increased density. In 8 cases examined by MRI, enlarged iliopsoas bursa appeared as low signal on T1WI and water-like high signal on T2WI. They also appeared as round or oval cyst with sharp rim on coronal section, and passed up and down along the iliopsoas muscle (tendon). Conclusion: CT and MRI can make a positive diagnosis for all patients with enlarged iliopsoas bursa