Stories from My Diary-rrhea (part III): Acute Large Intestinal Diarrhea (Acute Colitis)

by Dr. Laci, aka, Dr. Poop

Now that we've covered acute small intestinal diarrhea, let's talk about acute large intestinal diarrhea, aka, acute colitis.

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.

The blood seen with colitis is bright red, unlike the darker to black digested blood seen when the small bowel is the injured gut. 

The main functions of the large intestine are storage of fecal material and absorption of water.  When either of these is not working properly, the result is 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 mucous 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 like they do with small intestinal diarrhea because the small intestine is the one responsible for more absorption of nutrients.  With large bowel diarrhea, the pet is still getting the vitamins and minerals needed for the most part and therefore, they aren't dropping pounds when they have large bowel diarrhea.

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 you will be asked 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 the pet is exposed to stressful situations which could predispose him/her 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, and some parasites, like whipworms, shed infrequently, so your dog could be infected with 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.
 
Which tests are most appropriate for your dog will be determined by your veterinarian.

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 their is a more severe systemic disease occurring.

In summary, here is a list of some of 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. Please keep in mind that multiple fecal tests may be needed, and some fecal tests may need to be repeated 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.

Related articles:
A Tale of Many Tails—and What Came Out From Underneath Stories from My Diary-rrhea (part I)
Acute Small Intestinal Diarrhea
Acute Large Intestinal Diarrhea (Acute Colitis)
hronic Large Intestinal Diarrhea
Chronic Small Intestinal Diarrhea

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Laci Schaible has always been an animal lover and wanted to be a veterinarian since the third grade. Eager to actualize her dreams, she left home and started college with a full scholarship at the age of 16. She graduated with honors at the age of 19, and then became one of the youngest U.S. trained veterinarians in history when she graduated with her D.V.M. at the age of 23 from Texas A&M University.

After practicing as an associate at an emergency / referral and general practice small animal hospital, she was anxious to lead and manage her own hospital, which she successfully did for years. Performing surgeries with her husband Jed (also a vet) is one of her favorite aspects of practice.

Together, after losing their beloved family dog Madison to terminal cancer, Laci and Jed realized the need for pet owners to have affordable unbiased guidance for their pet's health care beyond their veterinarian with office hours. 

Jed's entrepreneurial genes and Laci's creative passion motivated them to fill this need, and VetLIVE.com was born.  Check out their blog for a mix of pet health advice, funny stories from the vet perspective, and even cool video blogs from Dr. Jed!

You can also follow Dr. Laci on Twitter  or VetLive on Twitter  or Facebook.