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Friday, May 27, 2011

Broken Chip?

Post 501.  Let's keep going!

Here's a question from Esther...

I found your microchip blog posts and have a question for you:
Have you ever had seen or heard of a case of a chip (AVID) breaking up into two parts and one part migrating?

I just found a tiny lump on my cat halfway doen his back (about 5 inches from the original implant between his soulderblades, which is still detectable) and it feels just like a microchip! I took the cat to the vet and she agreed that it felt like a chip. Also, both sites scanned and displayed his AVID#!(NOT two different numbers, so it does not appear to be a chip that might have been implanted into my cat before I found him, when he was an unneutered, hungry stray.) Now, I suppose the scanner could have picked up the chip located 5" away from the site of this new-found lump.

My vet did not have any other idea what the lump could be ("I have never felt anything like it.") and recommended having it surgically removed to find out. (The lump is too small and too movable for a needle biopsy to make much sense.)

I will porbably follow her advise and have his teeth cleaned while he is under anesthesia. Still, I would like to find out first if there is a possibility of this being (part of) a migrated chip. Would it still scan if it had broken in two?

Thanks for your thoughts on this (if any)!

Yes, I know this is more fodder for the anti-microchip crowd, but I thought it was worth bringing up.

First, this is not a common problem.  Chips migrating are known, though uncommon, but a broken one is much less common.  Theoretically a broken chip could continue working, though it would be much more susceptible to damage.  The outer shell of a microchip is essentially protective, allowing it to be inserted without the inner workings making direct contact with the tissues. It's usually a sterile, non-reactive glass and has small holes for fibrous tissue to adhere to, therefore reducing the risk of migration as scar tissue "locks" it into place.  The smooth surface makes it slide into the tissues easily, allowing less trauma during implantation.

Since the outer casing serves no direct function in the chip's working once implanted, I could see a situation where it breaks or comes apart.  The casing and the inner parts could migrate to different locations, resulting in two different "lumps".  If there isn't too much trauma in the area, the actual working parts could continue functioning without the shell, allowing it to broadcast the chip number.  However, it would be much more likely to fail in the future as those parts would be much more easily damaged.  It's also very possible for a microchip's broadcast to be picked up several inches away (especially with 134 kHz chips), so you may be getting one signal from the chip and not in two locations.

I would agree with your vet's advice that it's worth surgically exploring this.  If it is the chip, I would recommend removing it and have a new one implanted (yes, I still advocate microchips and use them in my own pets).  Leaving it in place could lead to tissue irritation in the future or the chip could stop working.  If it's not the chip it sounds unusual enough to be worthwhile removing.

Good luck, Esther!


  1. Would be interesting to see an x-ray of this cat's lump and see if you can see two distinct microchip parts.

  2. Dr. Bern,

    Thanks for your detailed reply.
    As mentioned previously, the vet I took him to thought the lump too small and slippery for a needle biospy.(She said she might not get enough cells.)
    I don't know why she did not recommend an x-ray (would you?); I assume because if this lump were soft tissue, it would not show up on an x-ray.(Correct?) A microchip part would, but then it would still need to be removed, so why not just take it out?
    I had spoken to AVID's vet before contacting you. He said microchips usually don't even break up if a pet gets hit by car, say, so he did not think it likely my cat's had. Migration, maybe (although I can still feel the chip in its original location; I suppose what I am feeling COULD be scar tissue), but it would probably migrate down, not back.

    I am reluctant for my cat to undergo surgery, both for cost as well as for health reasons (he is FIV+ and I try to keep his life low-stress), but I think I'll still get it done next Friday. I'll let you know the results.

    Thanks again!

  3. The glass parts wouldn't show up as easily on an x-ray; generally we notice the metallic parts. Your vet is correct that very small lumps are very difficult to get needle samples of, and I also don't generally do it if it's very small.

    If I was planning on trying to do surgery I probably wouldn't x-ray this ahead of time, as it probably wouldn't tell me anything that would change my plan. If the chip had broken apart I'd want to take it out. If it wasn't a chip I'd want to remove the suspicious tissue.

    With an FIV+ cat I agree that you want to minimize stress and would avoid invasive surgeries unless necessary. However, this should be minimally invasive and shouldn't cause too much physiological stress. If it is this strange of a situation I'd probably go ahead and have it done.

  4. Thanks again for your thoughts and advise!

  5. Just wondering - I have never been a fan of microchipping (although I do really appreciate its value - I just don't like the idea of a foreign body inserted and would worry about infection). Were this cat mine, I would have the device removed and would not have a new one inserted incase the same thing happened - the cat is already ill and I wouldn't subject it to interventions that could cause it stress - some animals find a visit to the vet stressful even if the vets are the best in the world (thankfully my dog loves to go to the vet even when he has been really unwell - adores the nurses and vets and delights in a visit). I would imagine that the cat is not out roaming as s/he could infect other cats by coming in contact and if now an indoor animal I don't see the need for the microchipping again. But this is my own personal view and by the looks of it Dr Bern would not be in agreement (but hey I am a pet owner not a vet).

    I am wondering while on the subject - is there any truth in the "rumour" that research has shown cases where cancer has been detected potentially as a result of microchipping?

    Ester - best of luck with your cat.

  6. Quick update: I cancelled my cat's surgery date as I lost track of his lump a couple of days prior. I hope its disappearance is a good thing.
    I am still planning on getting his teeth cleaned sometime soon but want to wait a little to see if the lump shows up again.


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