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Despite thromboprophylaxis, we observed DVT in 27.2% of the cases. This incidence of DVT was less than the rates of 34-63% in previous reports3-9). In this study, thrombus mostly formed in the soleal vein, consistent with previous reports10, 11).In previous studies, the majority of thrombus cases were found in the lower leg and disappeared within a few days, but approximately 30% extended There was no significant difference in FDP values between the DVT-positive group and the DVT-negative group. DVT, deep venous thrombosis; FDP, fibrinogen degradation productsThe DVT-positive rates in all cases were 3.0% pre-operatively, 9.0% on POD 0, 20.0% on POD 1, 18.1% on POD 3, 18.1% on POD 7, 16.3% on POD 14, and 16.3% on POD 21. POD, post-operative day; DVT, deep venous thrombosisFigure 2　Changes in FDP valuesFigure 3　DVT-positive ratesto the proximal side within a few weeks12-14). Thrombus that develops on the proximal side tends to become free-floating within a short period, leading to widespread pulmonary thromboembo-lism15). Therefore, the source of embolization for severe PE is often proximal to the popliteal vein, particularly the femoral vein. However, it can some-times occur on the distal side11, 15, 16), and from the 495