A cat with a big belly but very lively does not necessarily mean ascites. It may also be caused by indigestion, pyometra, etc. You can gently pat the cat’s belly to see if there is any fluctuation. If there is fluctuation, then It may be ascites and needs to be sent to the pet hospital for examination and treatment in time.
Tips:
You can feed the cat some probiotics and observe for two days if there is no improvement or if other symptoms appear, it is best to send it immediately medical treatment.