Are you sure he's neutered? Are you sure he's male?!?!?! :)
Seriously...this is hard without seeing him. Assuming he's not just getting *really* fat...most intestinal disorders make cats thinner, and the ones that cause bloating usually leave no appetite.
Can you tell me if you can handle him at all (touch him)? If so, press gently about the bloated stomach region. If it's solid feeling/hard...well, just let me know what you feel. Try to describe how the fur feels, the skin, if it feels squishy (not in a healthy way), and how he reacts to pressing. Try in a few spots (pressing).
Is his behavior changed at all, and how long has h been like this? I can think of 20 possible things it could be, but need to narrow it down. At least half can be cancelled out if he's been like this more than two days, since those things lead to a fairly immediate death...
The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Med Help International, Inc. is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.