From:
Bruce Williams, DVM
Date: 2001-11-12 15:25:00 UTC
Subject: Re: Ultrasound as way to test for tumors?
--- In Ferret-Health-list@y..., "Lynn Siegel" <gypsi@a...> wrote:
> Awhile back I had a ferret that had x-ray's & according to the tech
reading
> them, the ferret had several health problems, enlarged heart, was
one & it
> looked like she may have a tumor near her stomach. So they did a
ultrasound
> on her, it was ultrasound with color Doppler, whatever that is.
According
> to that everything was ok. I have read many times in the FML that
> ultrasounds don't necessarily show tumors, especially in adrenal
glands.
> When I mention this to the vets, they insist that ultrasounds
always show
> tumors. So how good is a ultrasound to determine if a ferret has
tumors or
> not? Is it reliable? Is just having an x-ray better? Should you
have both
> done?
Ultrasound and X-ray are both useful tools in detecting neoplasms,
but both rely on showing the outline of a neoplasm, and generally
work only if there is marked enlargement of a normal structure.
However, like any diagnostic test, it has its limitations. Because
adrenal neoplasms may be small enough not to cause enlargement of the
gland, these may be missed with both ultrasound and X-ray, and
diagnosed only on clinical signs, or elevated levels of estrogen or
its precursors in the blood.
Here is a common scenario - ferret presented for clinical signs of
symmetrical baldness. Ultrasound is scheduled. Well, as soon as the
clinician walks in and sees the bald ferret - he or she is
immediately geared to seeing an enlarged adrenal gland, and is likely
to see one regardless of what the monitor shows. It's unavoidable
bias, and a test whose outcome is so predestined, it's not valid.
This is one of the reasons that I generally recommend going to
surgery if the clinical signs fit the profile, and not waiting for
ultrasound to be performed.
Ultrasound and x-rays are good tools in the diagnosis of neoplasia,
but only that. The statement that it always finds the tumor is
patently overstating its significance.
With kindest regards,
bruce williams, DVm