Hello, my name is***** and I have over 20 years of experience as a veterinarian. I'm sorry to hear about Hershey's chronic loose stools that improved with a diet change, antibiotics and probiotics but worsened again off these things.
It will be important to describe what sort of loose stools she has to try and localize the problem. Loose stools with mucous or bright red blood, increased frequency and straining point more towards large bowel diarrhea or colitis
, whereas just loose stools with no mucous, and no increase in frequency, point more toward small bowel disease.
Chronic diarrhea does cause changes in motility of the gut and can lead to reflux and vomiting. It can also lead to bacterial overgrowth in the gut, so it makes sense that probiotics such as Fortiflora or Benebac can help because they replace appropriate bacteria. It is fine to use these as needed.
I assume that she has had stool samples checked to make sure that parasites aren't part of her problem. Have any other diagnostic tests been checked?
Has she had a fecal culture to check for abnormal bacteria such as clostridia?
Has she had blood levels of cobamalin and folate checked to look for abnormalities which indicate small intestinal disease.
Is she losing weight?
It is quite possible that she has a food allergy/sensitivity or inflammatory bowel disease
and that she needs to eat a low residue, easy to digest food or a hypoallergenic
food to be able to properly digest and absorb her food and not have loose stools. I'm not sure what she had previously but I recommend a trial of either Hills i/d or Purina Veterinary Diets EN. No treats
, table food or edible chewies while she is on her food trial. If she does well she can eat these foods for life as they are balanced. Having had 2 dogs with inflammatory bowel disease I have a personal preference for Purina Veterinary Diets EN. Dogs with food allergies can benefit from Hills z/d or Purina Veterinary Diets HA.
Dogs with inflammatory bowel disease will worsen with stressful situations. There may be times when she will need medications too, such as metronidazole or even steroids if that is her problem, but I have found that a consistent, easy to digest diet is very helpful for long term control.
There are other possibilities too.
Addison's disease, which is a poorly functioning adrenal gland, can lead to chronic diarrhea and vomiting. These dogs cannot handle stress at all because their adrenal gland doesn't produce cortisone when stressed and their electrolytes can be off too if their adrenal gland isn't controlling that normally either. We see vomiting, diarrhea and sometimes physical collapse in severely affected dogs. Testing is an ACTH response test to check adrenal gland function and checking electrolyte levels. Treatment is steroid replacement therapy and electrolyte replacement.
Pancreatic insufficiency is another possibility. These dogs have a pancreas that produces a decreased amount of digestive enzymes, and the amount produced can wax and wane in some cases, especially early in the disease process. Testing is by running a blood test called a TLI which checks for digestive enzymes. Treatment is replacement of digestive enzymes at each meal. An easier to digest food would be expected to create less problems with digestion and as such less diarrhea.
Kidney and liver disease can cause diarrhea too, but I would expect her to be sicker in general and diarrhea shouldn't improve with a change in diet. We check for these by running a blood test called a biochemistry panel.
In short since this has been a chronic problem for your girl then more diagnostics need to be done.
Testing can be as simple as fecal checks and cultures, as well as a complete blood count and biochemistry profile to assess general health. Further blood tests such as cobamalin and folate levels or checking for pancreatic insuffuciency would be reasonable too.
Or testing can be more invasive such as biopsies of her gastrointestinal tract to look for inflammatory bowel disease or infiltrative cancers such as lymphoma
Please let me know if you have any further questions.