Adrienne is a certified dog trainer, behavior consultant, former veterinarian assistant, and author of Brain Training for Dogs.
IBD in Dogs: A Diagnosis of Exclusion
The diagnosis of inflammatory bowel disease (IBD) in dogs is often a diagnosis of exclusion. This means that other medical conditions that are known for causing similar symptoms may need to be ruled out first.
In the medical and veterinary field there is a saying "when you hear hoofbeats think horses, not zebras." What this saying means is that when a patient presents with certain symptoms, doctors should think of the most common conditions first and the less common ones should be considered only once the most common ones have been ruled out.
So for example, a person presenting with a runny nose should be evaluated for the common cold, flu or allergies before thinking of some rare tropical disease affecting less than 10 percent of the population!
The process of screening through several conditions in an almost orderly fashion is known as differential diagnosis. In a differential diagnosis, the doctor or vet will be screening through conditions that share similar signs or symptoms with the most common ones excluded first.
There are many pathologies that may affect a dog's digestive tract. Sorting through them can prove to be quite a diagnostic challenge. It appears that veterinarians are sometimes too quick in making a tentative diagnosis of IBD in dogs.
"The term IBD is thrown around quite a bit and is markedly overdiagnosed in chronic gastrointestinal cases....When it comes to IBD, idiopathic inflammatory bowel disease (IIBD) is a more accurate term, remarks Dr. Craig Ruaux a board-certified veterinarian specializing in internal medicine.
Idiopathic IBD is diagnosed by systematic exclusion of all known causes of chronic intestinal disease in dogs. It is difficult to clearly differentiate food reactions (including food allergy) from IBD.
— Dr. Johnny D. Hoskins, board-certified veterinarian specializing in internal medicine
Bloodwork and Urinalysis
The symptoms of IBD in dogs tend to vary based on the site of the GI tract that is affected. Involvement of the dog's stomach results in vomiting, involvement of the dog's small bowel results in diarrhoea and weight loss, and when the dog's large bowel is involved, dogs develop diarrhea with mucus and blood and tenesmus (straining to produce only a small amount or just drops diarrhea).
These are all quite vague symptoms that can be caused by a great variety of disorders that may or may not stem directly from the GI tract.
A good place to start for the process of exclusion is by running a complete workup starting with some blood tests. A complete blood count and a biochemical profile can provide important information pertaining the correct functioning of organs and may help in the ruling out process of several disorders.
These blood tests can help rule out, or at least screen, for some other disorders that may cause digestive issues such as liver disease (elevated liver enzymes), typical Addison's disease (electrolyte imbalances) and some types of parasites (especially when there is increase in the number of eosinophils).
Furthermore, specific blood tests such as a GI blood panel test (which comprises several tests) may be needed to determine whether there might be a primary gut problem at play. Such blood tests may include serum trypsin-like immunoreactivity(cTLI) and Pancreatic Lipase Immunoreactivity (PLI) to screen for issues of the pancreas.
Folate and serum cobalamine (vitamin B12) blood tests may also turn helpful as their decreased levels may be seen in chronic GI diseases and malabsorptive disorders such as intestinal bacterial overgrowth (SIBO), also known as “antibiotic-responsive enteropathy”. This makes senses considered that both folate and B12 are absorbed by the dog's small intestine.
If your dog has a history of exposure to stagnant freshwater such as swamps, ponds, lakes and rice paddies in the last several months, your vet may also want to screen for Pythium insidiosum, a fungal parasite found in water. This can be screened through a blood sample (ELISA testing of serum for pythiosis antibodies). Pythium is quite rare, but it has been reported in several Southern Gulf states such as Louisiana, Florida, and Texas.
Another condition that may cause symptoms similar to IBD in dogs is histoplasmosis. This condition is caused by a soil-dwelling fungus known as Histoplasma capsulatum which thrives in warm, moist environments within soil contaminated with bird or bat manure.
When the intestinal tract is involved, affected dogs develop persistent diarrhea, bloody stools and straining when passing a bowel movement which can be confused for IBD. Blood work in affected dogs may reveal anemia and other abnormalities.
A urinalysis can too be helpful to exclude other non-GI diseases causing vague symptoms of GI problems. .
It may not seem like it, but your dog's poop can provide quite an insight into how well your dog's digestive system is working. If you are planning to drop off a fecal sample for a fecal test, make sure that it's pretty fresh (the fresher the better). Let your vet know at what time you collected it and label the bag with your dog's name and your last name and contact information.
In particular, your vet may be on the lookout for some types of parasites that may cause digestive problems that may mimic IBD such as giardia or whipworms..
If your dog has large bowel diarrhea (diarrhea that starts in large amounts at first, and then your dog is straining producing a few drops and there is mucus and blood in it and your dog isn't losing weight and still has some appetite) your vet may want to exclude the presence of whipworms (trichuris).
Whipworms tend to live in the dog's large intestine where they cause severe irritation leading to watery, bloody diarrhea, dehydration, weight loss, anemia and general malaise. Foxes and coyotes are regular hosts for this parasite and therefore may function as reservoirs for whipworm infestations.
Whipworms are diagnosed when the vet finds the presence of eggs in the fecal sample when using a microscope. However, just because there are no eggs doesn't mean there are no parasites.Unlike roundworms or hookworms which release eggs at a rather steady rate, whipworms are tricky as they have a tendency to release eggs on an irregular basis which means that it may take several stool samples to stumble upon them.
Because of this, dogs presenting with chronic large bowel diarrhea may be given a dewormer effective against whipworms (like Fenbendazole generic of Panacur) just in case even if the stool sample tests negative for parasites, explains veterinarian Dr. Ernest Ward.
Note: if your dog is on monthly heartworm medication, there are chances that his monthly medication includes drugs that are meant to prevent whipworms. Heartworm medications that are capable of preventing whipworms include Interceptor Plus, Sentinel, Advantage Multi and Trifexis.
Whipworm eggs are passed with stools and are extremely resistant eggs. This means they survive very well in the environment. There have been reports of eggs in the environment that remained infective 5 years later. They are difficult to remove from the environment as well because they are so hardy.
— Dr. Kara, veterinarian
An abdominal ultrasound can be insightful so to rule out important differentials and screen for IBD in dogs. In other words, more than confirming IBD it confirms more what it's not.
The ultrasound can therefore help screen for cancers of the gastrointestinal tract such as lymphoma (often suspected when there is presence of enlarged lymph nodes within the abdomen) and adenocarcinoma. The imaging can also evaluate the state of internal organs such as the liver, kidneys and pancreas. Pockets of fluid may be suggestive of Protein-losing enteropathy (PLE) .
Dogs with IBD may tend to show mild thickening of the intestinal wall however, this may be present as well in dogs suffering from lymphangectasia which requires a different treatment. Both require a full tissue biopsy in order to confirm diagnosis.
X-rays may not be very insightful when it comes to IBD but may rule out other disorders such as intestinal blockages.
Definitive Diagnosis of IBD in Dogs
Definitive diagnosis of IBD in dogs entails obtaining a tissue biopsy of the small and/or large bowel. The tissue biopsy may be obtained surgically or by endoscopy or colonoscopy (upper and lower scope).
When obtained through endoscopy, a long, flexible tube with a small camera (endoscope) is inserted down the dog's throat until it reaches the small intestine. Here, the vet visualizes the GI tract from the esophagus down to the intestine and removes tissue samples for evaluation as needed. The endoscopy usually needs a referral to a specialist.
The tissue biopsies collected help the vet evaluate whether there is presence of inflammation, its location and severity. The biopsies will therefore help confirm the diagnosis of IBD in dogs. The most common findings in dogs with chronic diarrhea are found to be IBD, lymphangiectasia and lymphoma (Source: Veterinary Clinics of North America, Chronic Intestinal Diseases of Dogs and Cats. Volume 41 Number 2, March 2011)
- DVM360: A guide to canine parasiticides
- Batt Laboratories Ltd, TLI, Folate & B12
- Veterinary Clinics of North America, Chronic Intestinal Diseases of Dogs and Cats. Volume 41 Number 2, March 2011
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2018 Adrienne Farricelli
Adrienne Farricelli (author) on September 14, 2020:
Hi Peggy, I agree with your grandfather's view, it takes a lot of skill for vets to figure out what may be wrong with dogs. Fortunately, nowadays, there is a lot of sophisticated testing, but some vets still rely a lot on guesswork and give meds as a trial, if the meds work, then they guessed right, if not, they'll try something else. Sometimes they take this approach when owners cannot afford a lot of testing.
Peggy Woods from Houston, Texas on September 14, 2020:
My grandfather used to joke that vets were smarter than most doctors because the animals could not communicate the symptoms to the vet as people can do. Your article shows, through the process of elimination, diagnosis of the correct cause is determined in many cases for dogs with IBD. I find your articles fascinating and informative.