Hello, I'm Dr. Kara. I have over 20 years of experience as a veterinarian and I'd like to help with your concerns about Dominick's history of on and off vomiting, slightly elevated liver enzymes, now loose dark stools with some visible blood.
I understand blood tests two weeks ago showed a normal CBC and no evidence of diabetes, that his urinalysis was normal as was his physical examination. I also see that metronidazole has not helped and neither is a bland diet.
I absolutely think that Dominick needs to see his veterinarian for a recheck.
Black, tarry stools can indicate digested blood in the stools from gastrointestinal bleeding from things like gastrointestinal ulcers, viral infections, liver disease/failure, a blockage or damage from a foreign body, toxins such as rodenticides, tick borne diseases or a mass in the intestinal tract. His continued decreased appetite and consistent loose stools for a 2 week period of time show that this isn't a short term irritation from eating something he should not, but rather a true health issue.
At his age I would be most concerned about cancer, specially gastrointestinal cancer that has spread to his liver.
An ultrasound of his abdomen and radiographs of his chest to look for metastases could be very helpful.
What color are his gums and tongue? If they are very pale pink or white then he is in serious trouble.
If you absolutely cannot have him seen today all you can do at home is keep him very quiet, give him acid reducers in case this is related to painful gastrointestinal ulcers, try to get fluids in, and continue to offer a bland diet.
Acid reducing medications to try at home are either:
1) Pepcid-ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours.
These will reduce stomach acid and should help somewhat if this is related to gastrointestinal irritation. They are very safe medications and should be given until he is re-evaluated.
A couple hours after giving an acid reducing medication offer a bland diet of 1/3 boiled, lean hamburger (or boiled, white, skinless chicken), all fats and juices drained off the meat, mixed with 2/3 boiled, plain white rice, pasta or mashed potatoes. Feed several small meals a day.
If he refuses to eat try offering low salt clear broths like chicken or beef broth to get fluids in or ice cubes to lick.
Ideally he should be seen by his veterinarian as soon as possible given his long term symptoms.
Please let me know if you have any further questions.