Venograms are a radiograph-based contrast studies, using radiopaque dye, in which we evaluate the blood flow and circulatory status of the hoof. It’s probably utilized more with laminitic horses that any other pathology, but there are other situations where it can prove to be useful. The odd thing with laminitis is that for the many varying degrees of presentation and pain it displays, there is some degree of difficulty in trying to discern the magnitude of pathology present. For instance, we might be dealing with a particular case which has a few subtle changes radiographically (on x-rays), and seems to be in quite a bit of pain, clinically; there is a huge prognostic difference (i.e. what are the chances of recovery) in the possibilities that could be displayed venographically.
The basic technique involves placing a tourniquet just above the hoof, inserting a small iv catheter into one of the major veins of the foot, injecting the contrast dye, and taking radiographs so as to determine where there is and isn’t circulation to the hoof. Thought you might like to know.
We are usually concerned with the circulation in the front half of the hoof and the dorsal wall. With this type of information, we can monitor prognosis and either fine tune our treatment or make drastic changes as needed and/or indicated.
There are also other conditions where venograms are utilized; septic conditions of the coffin bone usually have areas where the bone has lost its blood supply and actually needs to be surgically removed. In this case there would be a lack of contrast dye in the area of the necrotic bone. Keratomas, which are tumor-like growths that occur within the hoof capsule, can be detected early on with the help of a venogram; at this point the venogram will better help map out a surgical approach when several options may exist. At a more advanced stage of development, keratomas can cause a significant amount of bone resorption within P3 (coffin bone); here the plain film radiographs become so much more obvious that diagnosis can be made without the help of the venogram, although the surgical approach info will still be useful.
Here we have lost medial/lateral balance (above)
This is a venogram of a horse whose circulation is fairly close to normal(she was a grain overload case and was developing laminitis at the time).
This is a horse in the serious “sinking” type phase of laminitis;notice the lack of circulation around the tip of the bone.
Here is the same horse about a month later;see how the circulation is improving around the tip of the bone.