Friend, you are right, when we see vomiting of undigested food it is called "regurgitation" as the food has not been digested. Possible causes could be esophagus disorders (megaesophagus, strictures, parasites), gastritis, or even part of a systemic disease. I am going to make some recommendations that you can try at home. If he continues to regurgitate the next step is a hands-on examination with your family veterinarian and x-rays as an initial screening test. This is what you can try:
1- Do not give things like Pepto Bismol or Imodium. Start him on Zantac (ranitidine) 75mg 1/2 tablet every 12 hours for the next 2-3 days. You can buy Zantac over the counter in any pharmacy (chemist).
2- No food for 8-12 hours. Need to give his gastrointestinal tract time to rest.
3- After 8-12 hours offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day. Keep on this diet for several days then wean into regular diet.
Note: When you feed him raise his eating dish on to a small stool to force him to raise his head when he is eating.
4- If he continues to regurgitate after doing the above he will need to be seen by your family veterinarian for a hands on examination and x-rays as an initial screening test.
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