Midcalf ultrasonography for the diagnosis of ruptured Baker's cysts.

Clinically significant and palpable enlargement of the gastrocnemio-semimembranosus bursa is known as a Baker's cyst. Baker's cysts may rupture, resulting in a swollen, painful leg that is clinically indistinguishable from acute deep vein thrombosis. For this reason, ruptured Baker's cysts are sometimes called pseudothrombophlebitis. The purpose of this study was to determine the incidence of ruptured Baker's cysts, and to evaluate the role of ultrasonography in the diagnosis of this condition. The hospital records of 106 patients (43 men and 63 women) who were referred to the vascular surgical department at Saitama Medical Center with unilateral or bilateral swollen legs between June 1997 and June 2000 were reviewed retrospectively. The total number of affected limbs was 125, being 52 right legs and 73 left legs. Deep vein thrombosis was the most common cause of swollen legs, being diagnosed in 44.8%. No specific anatomical derangement was found in 39 limbs (31.2%), and these were defined as idiopathic. Lymphedema was also common, being diagnosed in 16 limbs. Ruptured Baker's cysts were observed in three limbs, with an incidence of 2.4%. In all of these patients, a large hypoechoic space was seen behind the calf muscles and this sonolucent area was easily detected by a conventional scanner, being pathognomonic of a ruptured Baker's cyst.