Pulmonary embolism from a venous thrombus located below the knee.

A patient with bronchogenic carcinoma developed acute thrombophlebitis below the knee followed by pulmonary embolism. Sequential nuclear venograms, perfusion lung scans, bilateral impedance plethysmography, and the patient's clinical course indicated that the below-knee thrombus had embolized in its entirety, causing clinically significant disease. This case demonstrates that below-knee thrombi are not always benign and, in certain circumstances, merit anticoagulation.