In Issue 31 enlarged spleens came under scrutiny:
 
 Date: Sat, 03 Mar 2001 18:32:46 -0000
 Subject: Re: enlarged spleen
 
XXXXX is very correct on this one.  Let me add a little more detail.
Splenomegaly is a stereotypical response to chronic smouldering
inflammation in ferrets.  While it is most often seen in response to
chronic inflammation in the GI tract due to Helicobacter or prior ECE,
actually any chronic inflammatory condition can cause it.  Chronic
inflammation is a site of liberation for many chemicals (called cytokines)
which serve to attract other inflammatory cells, modulate the inflammatory
response,etc.  While most stay locally, a small amount gets into the
bloodstream and travels around.
 
These compounds have the ability to turn on the maturation of white and red
blood cells in the spleen.  This is not particularly unique to ferrets, and
we see it in other species as well.  The best proof of this phenomenon was
a study done about 15 years ago in rats.  A group of rats was injected with
sterile turpentine in the hind leg, which set up a chronic inflammatory
lesion (with no infectious component.) Lo and behold, five days later,
they all had enlarged spleens which were packed with immature white blood
cells - necessary for fighting this infection.  Red blood cells are
generally also produced in the spleen in inflammatory lesions, because
another side effect of chronic inflammation is a mild anemia in many cases.
 
95+% of enlarged spleens, when biopsy or aspirated, come back with a
diagnosis of "extramedullary hematopoesis" (the doctor name for a bunch of
immature red and white blood cells.)  Less than 5% are due to neoplasia of
the spleen (usually lymphoma, but occasionally you see vascular neoplasms.)
 
What do we do with enlarged spleens?  Well, if they get really big, they
can rupture.  Large spleens also can displace other organs and cause
ferrets to become lethargic and inappetent.  (Imagine if you had a 40 lb.
spleen inside you - you wouldn't feel tip top either!)
 
If there is no easily addressed site of inflammation, and the spleen is
large enough for the animal to be symptomatic, we pretty much just remove
it.  I have never seen splenectomized animals develop systemic infectious
disease, which is a concern in dogs.  Also, I have not really seen
significant benefits in ferrets due to the presence of maturing blood
elements in the spleen.  They never seem to get released into the
peripheral circulation - the spleen just gets bigger and bigger.  I've
seen critically anemic animals die with loads and loads of immature red
blood cells in the spleen.  So, to minimize the risk of rupture and make
the animal feel better, splenectomy is often performed, and is usually
successful.
 
With kindest regards,
Bruce H. Williams, DVM
 
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[Posted in FML issue 3349]