IT IS NOT unusual for edema of one leg to be considered insignificant by the physician or to casually be attributed to "phlebitis." Thus, investigation of the etiology of the swelling is not performed and correct diagnosis may either be delayed or even missed. This is particularly true when there have been recent episodes suggestive of thrombophlebitis or of conditions known to be conducive to venous thrombosis (such as bed rest, trauma, surgery, etc). Although the single most likely cause for unilateral dependent edema is thrombophlebitis, other conditions also may produce the same phenomenon. These less frequent causes must be considered in each case if the correct diagnosis is to be made and the proper therapy is to be instituted as promptly as possible.
Neoplastic disease causing lymphatic obstruction is well recognized as a cause for dependent edema. Such secondary lymphedema of the lower extremity may actually be the initial
Shieber W. Lymphographic Detection of Undiagnosed Neoplasms Causing Edema of Lower Extremity. Arch Surg. 1967;94(3):380-383. doi:10.1001/archsurg.1967.01330090074019