Role of venous duplex imaging of the lower extremities in patients with fever of unknown origin.

Background: Although a fever of unknown origin (FUO) is most often due to other causes, the few caused by pulmonary emboli, pelvic thrombophlebitis, or lower extremity venous thrombosis (DVT) present a diagnostic challenge. The purpose of this study was to evaluate the role of venous duplex imaging of the lower extremity in evaluating a large series of patients with FUO. This has not been reported previously in the English-language literature.

Methods: Medical records were analyzed of patients with FUO who were referred to the vascular laboratory for venous duplex imaging of the lower extremities to rule out DVT as a cause of their fever. A FUO was defined as a temperature of greater than 38.3 degrees C on several occasions for at least 3 weeks' duration that defied 1 week of hospital evaluation. DVT was considered as a probable cause of FUO if the following criteria were met: (1) a positive venous duplex image for acute DVT, (2) subsequent fever resolution within 7 days of anticoagulation therapy, and (3) a fever that was resistant to prior treatment.

Results: A total of 114 duplex examinations, gathered during a 2-year period, were analyzed. The 89 patients had a mean age of 58 years. Infections were the most common cause of FUO (57 of 89, 64%), and unknown causes constituted 19%. There were seven cases of DVT (8%), five (6%) of whom met the criteria for probable cause of FUO. The overall cost of venous duplex imaging examinations was $51,300 ($450 x 114 tests), with an average cost of $10,260 for each case of DVT detected as probable cause of FUO.

Conclusions: Consistent with the literature, infections remain the most common cause of FUO; however, DVT was found to be a more common cause of FUO in our present series (6%). The cost of venous duplex imaging of the lower extremities in establishing DVT as a probable cause of FUO should be borne in mind when the work-up of these patients is planned.