Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am very sorry to hear about Maxi's lethargy, refusal to eat, loose stools with blood and vomiting.
Of course anyone would be concerned about blood in the stool. The fresher the blood appears the closer the source is to her rectum.
The important factor in all of this is how your girl feels otherwise. If she felt great otherwise then that is a good sign. But her lethargy, vomiting and refusal to eat are huge red flags.
There is a condition in dogs called hemorrhagic gastroenteritis. These dogs have profuse dark, jelly-clot like, bloody diarrhea, often vomit and refuse to eat. They are very sick dogs and get dehydrated quickly so they need immediate care. Thus because she seems lethargic and is vomiting an emergency veterinary visit is best.
Uncomplicated colitis or inflammation of the large intestine, can be due to stress, a change in diet, parasites, a viral or bacterial infection, inflammatory bowel disease or even a food allergy. Rarely a mass in the colon can be the cause, or exposure to anticoagulant rodenticides. Another possibility is an anal gland infection. These are scent glands that are located just inside the rectum and an infection can cause a bloody discharge, though should not cause loose stools and certainly should not cause her to be lethargic or vomit.
A raw, irritated colon can take a few days to heal. Do you know if she got into anything that may have started all of this? The bleeding should clear completely with treatment over the next 2 to 3 days. Well worth checking at least a couple fresh stool samples too as parasite eggs/cysts are shed intermittently and they may be picked up on the second sample or third test even if the first is negative.
If you cannot have her seen by a veterinarian today we can try some things at home, but I am very concerned.
Since her appetite is off she may have some stomach upset and reflux that can go along with bloody stools.
To try and settle her stomach today you can try 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 if this is related to simple nausea and gastrointestinal irritation.
I would not feed her any food for 24 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 bloody stools. You can give her pedialyte to replace electrolytes too but Gatorade is much too high in sugar which can make her colon irritation worse.
Today even with the fast you can start Kao-pectate at 1ml per pound or 1 tablespoon per 15 pounds of body weight every 6 to 8 hours. This will coat her irritated gi tract as well as absorbing bacterial toxins. You can use it for several days until her stools look normal. You can find kao-pectate at the drug store. I like the kao-pectate formulation with kaolin and pectin better then Pepto Bismol as Pepto has salicylates which are in the same family as aspirin, and can further irritate the intestines.
If she has a tense painful abdomen, continues to have diarrhea with no improvement after being on kao pectate for 24 hours, becomes even more lethargic, continues 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.
But if she improves 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 2 tablespoon of canned 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 bloody diarrhea or vomiting for 48 hours and eating well) 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.
But because your pup is vomiting and feeling poorly though it would be best that she see a veterinarian now as anything you give her orally may just come back up worsening her dehydration.
Best of luck with your pup, please let me know if you have any further questions.