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Saturday, February 23, 2013

The Limits Of X-Rays

I'm back from vacation, so it's back to regular posting!

Here's a follow-up from my last post about Danica.

Since this email xray were taken Danica has calcium between her C3&C4 vertebra she is on tramidol for 14 days and methocarbonal and Prednisone for 30 days. Strict kennel confinement. I take her out to use the bathroom. The xray didnt show any bulging or no herniated disc. She is also on cod liver oil 1/4 tsp a day on her good.I would appreciate you feedback since the xrays

It's important to realize what radiographs can and cannot do.  The are great at analyzing bone and other dense objects.  They are great at looking at air patterns in the lungs.  They're pretty good at soft tissue structures and outlines.  Mineral and metal show up very well.  But they won't see everything.  

Some gastrointestinal foreign bodies have a similar "density" (we call it "radiopacity") to the surrounding tissues.  If we're suspecting something like cloth obstructing the stomach or intestines we typically won't see the object itself on the image because it blends in with the tissues.  So we have to look for other patterns, do a barium series, or have an ultrasound performed.

Intervertebral discs are another situation that doesn't show up well on a regular x-ray.  The discs themselves are not dense enough to view their borders.  Like in many cases we look for other signs that suggest a problem, such as a narrowing of the space between the vertebrae.  However, a normal intervertebral space doesn't necessarily mean that the disc isn't bulging or herniated.  It's possible to have a disc that is displaced enough to cause a problem, but not so displaced that it narrows the space.  These are tricky to diagnose because they simply don't show up on the image.  The only way to truly diagnose these cases is with a procedure called a myelogram, where a radiopaque dye is injected into the space around the spinal cord, outlining the cord and vertebrae and allowing detection of subtle narrowing.  Because this is a tricky procedure, it's normally done under anesthesia and by a specialist.

It sounds like Danica is on an appropriate treatment plan for now based on what you're saying.  Like I mentioned above, x-rays can't completely rule out a partially herniated disc, but the treatment for that is what she's already on, so in the end it may come out the same.  Continue to consult with your vet on this case.