Please help

My 15 years old cat suffers from lose of appetite and swollen abdomen from the right side, he is not moving as usual, sleeping all the day.but he doesn't look like he is in pain. sometimes his heart beat is fast and his legs shiver. but still he eats and purr and goes to the toilet normally.

Have you brought him to the vet?  I would recommend an emergency vet visit if not!  

Hanan ElGendy said:

 
My 15 years old cat suffers from lose of appetite and swollen abdomen from the right side, he is not moving as usual, sleeping all the day.but he doesn't look like he is in pain. sometimes his heart beat is fast and his legs shiver. but still he eats and purr and goes to the toilet normally.

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Cats don't always purr because they are happy.  Sometimes they purr to try to content themselves when they don't feel well.  They can actually try to heal themselves by purring, or so I've been told. 

Loss of appetite and especially the swollen abdomen don't sound  too good, so I would definitely get him in to be seen by a professional.  At least he is still using his litterbox, which is a good sign, meaning no blockage.  Is he both urinating and having bowel movements.  The Vet will need to know.

Thanks guys for answering.He is urinating and having bowel movement normally,the swollen got a little smaller today, I hope he will be ok.
mY vet isn't available till tomorrow.

Legs shivering usually means pain. From your description it could be a tumor, liver problems, or many other things. The only way to find out is an X-ray at the vets. I'll keep you both in my thoughts and prayers. All the luck!