Friend, I am sorry for the delay in response. I was offline by the time you came back. In response to your question when a dog is vomiting and is having episodes of diarrhea this can be caused either by primary problems occurring within the gastrointestinal tract or secondary to a systemic disease. The fact that she is an older dog and is drinking excessively I would want to rule out systemic diseases. You see, when a dog drinks more water than usual it is a sign an underlying medical problem. There are many possible causes. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: An active infection, hormonal disorders (diabetes
), kidney or liver disease and even cancer to name a few causes. The yellow color vomit is the presence of bile which is common with forceful vomiting. The straining when she defecates is a sign of inflammation in the colon (large intestines); these symptoms could be caused by any of the above mentioned diseases. Or, primary problems in the intestinal tract like: Infections, parasites, auto immune disorders (IBS), etc. In this case, to determine which of the above is the underlying cause your family veterinarian will need to do some blood work (chemistry profile, T4 & CBC) and urinalysis as initial screening test. If the blood work is normal then they may need to do additional testing like xrays or abdominal ultrasound. Treatment will be determined by clinical and diagnostic findings. In the meantime, this is what you can do for the vomiting: 1- Do not give things like Pepto Bismol or imodium. Start her on Pepcid AC (famotidine
) 10mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.2- No food or water for 3-4 hours. Need to give her gastrointestinal tract time to rest. 3- After 3-4 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. My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.