Dear Meesh Meesh:
 
>I have a question for vets and any owners who have had ferrets with right
>adrenal surgeries where the vena cava has been completely ligated (ie:
>tied off completely).  I know this is not routine but that it has been
>done and I am interested in hearing from vets and owners who had had
>ferrets go through such a procedure.  Any input would be great.  For
>example, what circumstances make this surgery more successful, less
>successful, post-op complications, survival rates, etc..anything you
>might have to offer would be appreciated.
 
Caval ligation is a salvage procedure reserved for ferrets with large
makignancies on the right adrenal gland whic 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,
comporimising and ultimately impleing 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, tothe
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.
 
With kindest regards,
Bruce Williams, dVM
[Posted in FML issue 3246]