Sonography in rheumatology.

The marked difference in acoustic impedance between bone and other adjacent soft tissues prohibits sonography from imaging internal architecture of joints and bones. Despite this, ultrasound is very useful in the assessment of many problems encountered in rheumatological practice. Sonography is unexcelled in its capability to rapidly distinguish between popliteal cysts and deep venous thrombosis. Additionally, ultrasound can readily evaluate synovial cysts occurring in unusual locations such as those presenting as a soft tissue mass in the thigh or arm. Because it is noninvasive, sonography is ideal in assessing patients with renal failure. This has been found to be extremely useful in patients who have systemic lupus erythematosus. Echocardiography and organ imaging capabilities are also useful in certain subgroups of patients with rheumatological diseases.