Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry that your pup Stella has had diarrhea for some time, but glad to hear that so far it hasn't led to lethargy nor is she vomiting.
Diarrhea of several days duration can be secondary to a heavy parasites infestation, but that is less likely in an adult dog. It can also be due to intestinal bacterial overgrowth, an inability due to digest and absorb food due to metabolic organ disease, (especially liver disease), pancreatic disease or endocrine disease (hyperthyroid, Addison's disease), or primary intestinal disease. In some cases it can be indicative of infiltrative intestinal cancer.
Dogs that have diarrhea for several days have abnormal gut motility, and thus may have some reverse gut motility or stasis and that can lead to nausea, thus a loss of or decreased appetite. The cramping that comes along with diarrhea also affects appetite.
It is important to describe what sort of loose stools she has to try and localize the problem. Loose, small stools with mucous or bright red blood and straining or increased urgency to pass stools more frequently point more towards large bowel diarrhea or colitis, whereas watery stools with no mucous, no increased urgency to go, and no increased frequency, along with weight loss point more toward small bowel disease.
Diarrhea does cause changes in motility of the gut and can lead to bacterial overgrowth in the gut. Probiotics such as Fortiflora, Proviable or Benebac can help replace appropriate bacteria.
If she has not had stool samples checked to make sure that parasites aren't part of her problem that should be done. Fecal cultures or smears to look for bacteria or unusual parasites that may be hard to pick up of a regular fecal can be helpful in diagnosis and treatment.
For now to try to treat her at home I do have some recommendations.
Since her appetite is off she may have some stomach upset and reflux that can go along with his loose stools.
To try and settle her stomach today you can give either:
1) Pepcid-ac (famotidine) at a dose of one quarter of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one quarter of a 20mg tablet per 5 to 10 pounds of body weight every 24 hours.
These will reduce stomach acid and should help if this is related to simple nausea and gastrointestinal irritation. These can be given for several days if need be.
I would not feed her any food for 12 hours after the acid reducers are started. This should help stop gut spasms and restore normal gut motility. Small amounts of water or ice cubes given frequently are fine as she needs fluids after all that she has lost with loose stools. You can give her pedialyte to replace electrolytes too.
Today even with the fast you can start Kao-pectate at 1/2ml per pound or 1/2 tablespoon per 15 pounds of body weight every 8 hours. This will coat her irritated gi tract as well as absorbing bacterial toxins.
If she has a tense painful abdomen, continues to have diarrhea with no improvement after being on kao pectate for 24 hours, becomes very lethargic, begins vomiting or runs a fever greater than 103.5F then she really must be seen by a veterinarian as soon as possible. Make sure to take a fresh stool sample with you when you go.
After her food fast start a bland diet of 1/3 boiled, lean hamburger (or boiled, white skinless chicken), all fats and juices drained off, mixed with 2/3 boiled, plain white rice. Feed several small meals a day. You might wish to add 1 tablespoon of canned pumpkin (not pie filling, just plain pumpkin) to each meal as fiber helps soothe an irritated colon. I recommend adding probiotics like Fortiflora, Proviable or Benebac to her meals daily to re-establish normal gut bacteria levels too.
Once she feels better (no diarrhea for 48 hours) start mixing in her regular dog food very slowly. Less bland more regular with each day. It should take a week or so to convert her back.
If this persists despite my recommendations for home care I recommend a fecal sample be sent to the lab for more specialized testing for parasites, a culture and a direct smear to check for abnormal bacteria such as clostridia ect..
I would also recommend basic blood testing be done, including a complete blood count, biochemistry profile and T-4 as well as cobamalin and folate levels. We want to make sure she has normal liver and kidney enzymes and blood proteins. Measuring cobamalin and folate will give us rough information about his small intestine's ability to properly function.
If this persists it is quite possible that she has a food allergy/sensitivity or inflammatory bowel disease and that she needs a different 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 highly recommend a trial of a sensitive stomach diet (Hills Science Diet and Royal Canin make these) or if those don't work prescription foods, 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. Dogs with food allergies can benefit from Hills z/d or Purina Veterinary Diets HA.
There are other possibilities too as I mentioned.
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.
In short diagnostics need to be done if her diarrhea persists. They can be as simple as more fecal checks and cultures, as well as checking pancreatic and/or adrenal gland function. An abdominal ultrasound could be very helpful. Or more invasive testing such as biopsies of his gastrointestinal tract to look for inflammatory bowel disease or infiltrative cancers such as lymphoma an be done.
In the meantime a diet change may help, and the addition of probiotics.
Please let me know if you have any further questions.