This study investigated the features of calf deep vein thrombosis (DVT
) as a pulmonary embolic source. Fifty-eight lower limbs in 29 patient
s who were suspected of having DVT distal to the popliteal vein were s
creened by ultrasonography. Then, ascending venography was performed t
o confirm the diagnosis. Pulmonary embolism (PE) was diagnosed in susp
ected patients by use of pulmonary perfusion scanning or pulmonary ang
iography. Venography revealed calf DVT in 33 limbs in 28 patients. Of
28 patients; six had symptomatic PE. Thrombosis was found in the muscl
e veins in 18 limbs, the trunk veins in II, and both veins in four. Is
olated single vein thrombosis was found in the soleal vein in 14 limbs
(42%), the posterior tibial vein in eight, the peroneal vein in two,
and the gastrocnemius vein in two. The overall percentage of soleal ve
in thrombi was 61%. All six patients with symptomatic PE had isolated
soleal vein thromboses. Calf DVT was a pulmonary embolic source when i
solated thrombosis of the large soleal vein was more than 7 mm in diam
eter. Soleal veins were the most frequent and important location of ca
lf DVT, suggesting that these were an occasional embolic source of cri
tical PE.