MRI mapping of postreconstructive edema following femoropopliteal bypass surgery.

We have used T1 MR images to map the distribution of water contributing to the edema which follows femoropopliteal bypass surgery. Spin-echo images and true parametric T1 images were made at the same time. The spin-echo images were used to identify the tissue anatomy. The extra fluid contributing to the edema distributes in two phases: a volume equivalent to 5% of the leg volume is distributed throughout the leg tissue, while the excess fluid collects in a localized annulus lying adjacent to the fascia. The T1 in the annulus can be as high as 4 sec, indicating build up of free fluid in this region. Although most of this free fluid lies in the subcutaneous fat, there is a component which lies underneath the fascia in the muscle compartment.