impedance plethysmography (IPG)

Impedance plethysmography (IPG) is used to measure the rate of venous drainage from the lower extremity in the evaluation of deep vein thrombosis (DVT). If there is an acute proximal (above the knee) thrombosis, venous drainage will be impaired & the test will be abnormal. The test has a sensitivity & specificity of 90% in diagnosis proximal DVT. It is not useful for evaluation of calf DVT. Causes of false positive tests include: 1) obesity 2) congestive heart failure IPG may be useful for evaluating resolution/recurrence of DVT, since most patients normalize with respect to IPG within 6-12 months of an acute DVT.

References

Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 283