Caval ligation is a salvage procedure reserved for ferrets with large malignancies on the right adrenal gland which have either invaded or severely compromised the posterior vena cava - the largest vein in the body. As the right adrenal sits directly on the cava, it is not uncommon that aggressive tumors on this side will either grow to a size where they block the flow through the cava, or directly invade the vena cava, compromising and ultimately impeding blood return to the heart.

Now, when this occurs, the body will attempt to establish collateral circulation through other vessels in the area to pick up the backup from the partially blocked vena cava. This phenomenon is the basis for vena caval ligation. If sufficient time has elapsed for collateral circulation to develop, then the cava can be ligated without harm to the ferret, allowing removal of the entire tumor. If not, and the cava is ligated, then you will see infarction of any number of organs in the body - most commonly the spleen and segments of the jejunum.

While there has been no peer-reviewed literature on the technique, to the best of my reckoning, having talked with many practitioners who are now performing it when necessary, the mortality rate is about 15% for this technique. This is why it is a salvage procedure - it is reserved only for cases in which there is no other way to remove the neoplasm, and you do take a risk when performing it. The key is that these animals will die shortly without it, so you are gambling that by removing the adrenal tumor and cava en bloc, you can save this animal's life.

There are many variables surrounding this procedure, and the ones that are most likely to determine the success of the operation is the amount of time the tumor has been there and the percent blockage of the vena cava. Surgical mortality will likely revolve around tumors that have frown to fast to allow collateral circulation to become viable, or those in which there is incomplete blockage of the vena cava (which will result in lesser collateral circulation development). Some vets have only rare mortality, far lower than the average, and some have 50% or more. For a surgeon, the most important ability is to be able to read the tumor to see if caval ligation has a chance of working in a particular ferret or not.

If you ligate the vena cava in a normal healthy ferret, you will assuredly get infarction and death. However, with adrenal tumors that have slowly occluded the vena cava over time, the body may well have compensated and the vessel can be safely ligated.

I think that it is important, however, that owners be told that this is a salvage procedure with a 15% rate of mortality up front. This is a last ditch operation, but you never want to go in, find an adrenal tumor, and close the animal back up.