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Dr Scott Nimmo
Dr Scott Nimmo, Small Animal Veterinarian.
Category: Cat Veterinary
Satisfied Customers: 19512
Experience:  BVMS, MRCVS. { Glasgow UK }
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My cat has swelling like a lump about a golf ball size on his

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My cat has swelling like a lump about a golf ball size on his left side right above his hind leg. Should i take him to an animal hospital? Is this an emergency or can i wait till morning?
Thanks for the question.

My name isXXXXX am an experienced small animal veterinary surgeon and I will be pleased to try and answer your question, but to enable me to do so with accuracy I need to know a little bit more information, so first can you answer the following questions concisely.

1. Did this come up suddenly?

2. How is he otherwise? Any other symptoms?

This is just an information request for which you have not been charged, I am online at present and will answer your question shortly after receiving your reply.


Scott Nimmo BVMS, MRCVS.

Please note it may take up to twenty minutes for me to consider your problem, perhaps look up some information and then type up your reply.
Customer: replied 5 years ago.
1) this did not come up suddenly. He had an injury before and I'm guessing it was agitated and the swelling came back.

2) Other than tenderness in his upper hind back quarter and the lump he seems fine.

It did not come up suddenly. He is an outdoor cat and one day, about two weeks ago, he came home and had some swelling in the same place. He seemed agitated and avoided contact with me. It seems like he is in pain whenever we touch his rear upper back and upper sides. He doesn't have any other symptoms that I can see. When he first came home with the injury there did not appear to be any external problems.
Thanks for the quick reply.

While I cannot diagnose Rudy's problem via the internet I can make the following general comments :

The most likely diagnosis here would be a cat bite abscess given he is an outside cat, the original bite could have happened quite a few days ago. You see cats are not the most sociable of creatures and they are prone to fighting, their canine teeth are long and sharp and covered with pyogenic [ pus forming ] bacteria. In fact when one cat bites another cat and really sinks its teeth in you can expect an abscess to form as a matter of course and this is more than likely what has happened in Rudy's case.

The usual treatment for a cat bite abscess would be a weeks course of antibiotics although some may need lancing and flushing out under anesthesia as well. This does mean a visit to your vet but in most cases it would not be an acute emergency and would wait until tomorrow.

If I have not covered your question fully enough or you would like to ask more I will be online for the next hour or so and I will be at your disposal.


Scott Nimmo BVMS, MRCVS.

I have over twenty five years full time experience in treating domestic pets and am pleased to do my best to advise you with your current problem. However please note that this advice and any subsequent advice I may give is for your interest and education only and is not intended as a substitute for an in-person consultation with a qualified veterinarian.
Customer: replied 5 years ago.
When he was first injured he had swelling in the same spot. Then he was fine after a few days rest and the swelling was gone. Now it has returned. When he was first injured he did not have any external marks on him and we checked thoroughly which in my mind rules out the possibility of a bite but I concede that I'm not sure about how a cat would bleed in this circumstance.
Hello again,

Glad to talk this over with your further ...

Actually what you are seeing is quite common, if the original bite was a few days back then the original bite marks may not be visible or will now be hard to see. If there was any pus left under the skin which would have been possible if the cat was not treated at that point then some time later an abscess may form under the skin and present just as you describe.

Sometimes they can be quite big but they are rarely life threatening. Also Rudy is now at the age where he will be becoming sexually mature and so his instinct will be to fight other cats and finally there is very little other than an abscess which will present in this age group.


Customer: replied 5 years ago.
Thank you for your answers so far,

One thing i'm not clear on is why there was swelling at first when he was injured and then it disappears only to return three weeks later.
Hello again,

This is not unusual, the original bite wound could have drained while he was out somewhere and then he would have licked it clean, this original wound could have been quite small by the way.

However if there was enough pus left under the skin to fill the eye of a needle then the abscess can come back at any future point { sometimes with a vengeance! }. You see the body will always try to wall off small areas of infection like that but often they break out again.

Of course all this is just guessing but your vet will most likely stick a needle in the swelling and draw back, if you see pus then that's your diagnosis!


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