Large intestinal diarrhea (both acute and chronic) is often seen in young or debilitated dogs.
A closer look at acute large intestinal diarrhea tells us it is acute nonspecific inflammation of the colon. The inflammation causes mucosal damage which results in bleeding.
What does acute colitis on dogs look like?
The blood seen with colitis is bright red. This is unlike the darker to black digested blood with the small bowel issues.
The main functions of the large intestine are the storage of fecal material and the absorption of water. When either of these is not working properly, the result is the failure to store stool (increased urgency in defecation) and soft to watery stools.
Indicators that your dog is suffering from large bowel, not small bowel diarrhea:
- semi-formed to liquid feces
- fresh blood or mucus in stool
- increased frequency of defecation (six or more times daily)
- straining, an urgent need to go
- and no weight loss.
Patients don’t lose weight as they do with small intestinal diarrhea. The reason is that the small intestine is the one responsible for more absorption of nutrients.
With large bowel diarrhea, the dog is still getting the vitamins and minerals they need for the most part. Therefore, they aren’t dropping pounds when they have large bowel diarrhea.
Diagnosing acute colitis
The good news about acute large intestinal diarrhea is that it is easier to break down and diagnose than other causes we have talked about so far.
In fact, far more than 50% of the cases I have treated of acute large bowel diarrhea have parasitic or dietary causes.
Where I start as the veterinarian is with a thorough history.
Things your veterinarian will ask you about include
- any medications your pet is on
- dietary indiscretion (potential of eating spoiled food or foreign objects
- dietary allergy or intolerance (less likely to be an acute cause, but possible with a food change)
- contact with other animals, and
- exposure to stressful situations which is a predisposing factor to bacterial overgrowth
If supportive treatment (withholding food then reintroduction with bland food) has failed and you find yourself at your vet’s office, fecal tests are likely to be a starting point.
Unfortunately, there is more than one type of fecal test. Some parasites, like whipworms, shed infrequently. This means that your dog could have whipworms and the test be negative if the worm wasn’t shedding eggs at the time of the test.
The different types of fecal tests are
- direct smears
- fecal floatation
- tests specific for specific parasites (Giardia being an example), rectal cytology, and
- even fecal cultures
Your veterinarian will determine which tests are most appropriate for your dog.
If your dog is otherwise clinically ill or your veterinarian finds abnormalities on the physical exam, even further diagnostics may be needed.
If your vet requests to do these tests (such as a blood cell count and chemistry panel) they are trying to rule out causes of diarrhea that are non-GI in origin, or affecting the GI tract and causing the side effect of diarrhea when there is a more severe systemic disease occurring.
In summary, here is a list of some of the causes of acute colitis:
- whipworms (Trichuris vulpis)
- garbage gut
- Coccidia spp.
- Giardia spp.
- bacterial causes (Clostridium perfringens, E. coli, Salmonella, Campylobacter spp)
- and food-induced allergic colitis
Like I promised, an easier list to sort from. A diagnosis might require multiple or repeated fecal tests to try and catch those sneaky intermittent parasites. Try not to be frustrated with your vet; it is a frustrating place to be in when don’t have the answers for you.
The good news is most cases of acute colitis will be solved and resolved within 72 hours.
Symptoms to Watch for In Your Dog: Diarrhea
A Tale of Many Tails—and What Came Out From Underneath
Acute Small Intestinal Diarrhea
Acute Large Intestinal Diarrhea (Acute Colitis)
Chronic Large Intestinal Diarrhea
Chronic Small Intestinal Diarrhea
Colitis in Dogs