Friend, vomiting can be caused by either primary disorders affecting the gastrointestinal tract or secondary to a systemic disease. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: Pancreatitis, dietary indiscretion, ingestion of a foreign body, infections or even part of a systemic disease, etc. to name a few causes. The fact that this has been going on for 4 days I would strongly recommend a hands on examination by family vet today, blood work and xrays as initial screening test. In addition, he may need supportive care (IV fluids, antiemetics, etc.). In the meantime, in any case of vomiting the first thing to do is give the stomach time to rest. This is what you can do:
1- Do not give things like Pepto Bismol or imodium. Start him on Pepcid AC (famotidine) 20mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 4-6 hours. Need to give his gastrointestinal tract time to rest.
3- After 4-6 hours offer a small amount of water. Wait half hour, if no vomiting, offer 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.
4- Follow up with your family veterinarian for a hands on examination. If cost is a concern look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
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