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What is Chronic Diarrhea in Dogs?
Diarrhea is one of the most common reasons pet parents take their dogs to the vet. Diarrhea is an increase in the frequency and/or looseness of stool.
Diarrhea is not a disease itself, but rather a sign of an underlying problem. When diarrhea occurs, food moves through the digestive tract faster than normal. The digestive tract absorbs fewer nutrients, electrolytes, and water. Sometimes diarrhea is urgent, and pets are unable to hold it, and accidents happen in the house. Other times, pets are able to hold it, but have loose or liquid stool instead of firm stool when they have bowel movements outside.
Diarrhea often clears up on its own, but chronic diarrhea can lead to dehydration, lethargy and vomiting.
There are two types of diarrheas in dogs:
Acute diarrhea occurs suddenly and resolves either on its own, or with treatment.
Chronic diarrhea or chronic enteropathy (CE) occurs when dogs don’t respond to common treatments for diarrhea, or when they do respond to treatment initially, but the diarrhea continues to return. Diarrhea is considered chronic when it lasts more than 2 weeks.
Is Chronic Diarrhea an Emergency?
Chronic diarrhea is rarely an emergency but can lead to dehydration and malnutrition, which may progress to systemic illness, organ shutdown and even death when not appropriately treated. If your dog vomits frequently, cannot keep down food, acts lethargic, weak or depressed, this may be an emergency and should be seen by a vet as soon as possible.
Causes of Chronic Diarrhea in Dogs
Chronic diarrhea can be frustrating for pet parents and uncomfortable for the pet. There are several different ways diarrhea can occur in dogs. It may occur because the body does not absorb nutrients appropriately, the intestines are inflamed, there are increased secretions, the intestinal walls are leaky, or the intestinal muscles are not functioning properly.
The most common causes of chronic diarrhea are:
Food sensitivity or allergy
Inflammatory Bowel Disease (IBD), a condition where the intestines are inflamed (possibly due to an autoimmune disease).
Exocrine pancreatic insufficiency, in which the body fails to produce enough enzymes to digest fats, proteins or carbohydrates.
Other underlying disease
Diarrhea is often classified into either small intestinal or large intestinal diarrhea. When a dog swallows food, it travels from the mouth down the esophagus to the stomach. From there it enters the small intestine, and finally the large intestine before being passed out as stool.
Both small and large intestinal issues can result in either acute or chronic diarrhea.
When pets have small intestinal diarrhea, diarrhea is usually large in volume, with a slight increase in frequency. It may be accompanied by vomiting and weight loss.
Large intestinal diarrhea tends to occur in relatively small amounts several times throughout the day (generally more than 5 times per day). It can be accompanied by bright red blood.
Sometimes diarrhea occurs secondary to causes not related to the intestinal tract. This is often seen with organ disease, like pancreatitis (where the pancreas is inflamed) or liver and kidney failure.
Some breeds, like Soft Coated Wheaten Terriers and Yorkshire Terriers are genetically predisposed to protein-losing enteropathy. Other breeds, like Boston Terriers and Boxers, can get intestinal lymphangiectasia and/or ulcerative colitis, leading to protein loss in the stool. These diseases can be picked up on screening bloodwork but are often confirmed with additional testing. Often, these conditions show similar symptoms to chronic diarrhea.
How Veterinarians Diagnose Chronic Diarrhea in Dogs
Chronic diarrhea is diagnosed when a pet does not respond to normal treatments for diarrhea and it persists for more than 2 weeks, or when they have recurring bouts of diarrhea that never completely resolve.
To identify the root cause of chronic diarrhea, veterinarians first must rule out any underlying conditions. Your vet will perform a complete physical exam and, depending on your dog’s medical history, will recommend tests to check for the following potential causes:
Parasites: Your vet may run a fecal float test to check for parasites, one of the most common causes of both small and large intestinal diarrhea. Hookworms can reside in the small intestines, feeding on blood, and potentially resulting in anemia in affected pets.
Whipworms, on the other hand, live in the large intestines and cause chronic, watery diarrhea as they steal nutrients from their host. Additionally, some parasites, like giardia, are very easy to miss in fecal float tests.
In patients with chronic diarrhea, many veterinarians will treat pets for parasites to ensure they have eliminated that common cause. Fortunately, many heartworm preventatives will also prevent several of the intestinal parasites.
Diet: After a thorough physical exam, fecal tests, and deworming, many veterinarians will explore diet therapy next to identify any sensitivity to specific food ingredients.
There are several different diet therapy options. Some diets are specifically formulated to be bland and have added prebiotics and probiotics, while other diets are designed to be hypoallergenic.
In most patients, the protein source (meat) is usually the culprit for food allergies. Many hypoallergenic diets have a “novel protein,” or new protein source that your pet has likely never been exposed to, like kangaroo meat or venison. Other hypoallergenic diets have hydrolyzed proteins, which are proteins that are broken down so small that they do not bind in the same receptor so that the immune system doesn’t have the same reaction to the protein.
If your veterinarian recommends a diet trial, it is important that you follow the directions exactly. Your veterinarian may recommend testing your dog for food allergies.
Underlying disease: If a dog with chronic diarrhea does not respond to deworming or diet therapy, a vet will run more diagnostics. It’s important to make sure that your dog doesn’t have any underlying systemic diseases that are contributing to their chronic diarrhea.
To establish a baseline your veterinarian will likely recommend running blood work, a urinalysis, and x-rays of your dog’s abdomen. Depending on results from these tests, your vet may decide to investigate further. For example, if your dog has very low proteins, your veterinarian may decide to explore common causes of protein loss in dogs.
Chronic Enteropathy: Irritable Bowel Disease (IBD) is a condition where the gastrointestinal tract is chronically inflamed. Either the small intestine, large intestine or both can be affected. Dogs with IBD may have vomiting in addition to diarrhea. Many patients have decreased appetite and lose weight as well. Testing usually involves additional blood work sent out to an external laboratory.
Infectious disease: Contagious organisms, like bacteria and viruses, can cause chronic diarrhea. Your vet may recommend fecal PCR panels to screen for the more common offenders like clostridium. Some chronic diarrheas can be bacterial in nature due to persistent intestinal overgrowth of bacteria. These conditions may respond to long-term low dose antibiotic therapy.
Refractory diarrhea: Occasionally patients will have refractory diarrhea, which is chronic diarrhea that does not improve with treatment, and tests are not providing answers. These can be tricky cases requiring additional imaging (like ultrasonography) and potentially intestinal biopsies to determine the underlying cause. While uncommon, there are gastrointestinal cancers that can cause chronic diarrhea.
Recovery and Management of Chronic Diarrhea in Dogs
It is often recommended to switch to a bland diet if a dog develops acute diarrhea.
Pay close attention to the frequency and consistency of your dog’s bowel movements and share with your doctor any changes along the way. In order to get to the underlying cause of chronic diarrhea in your dog, it’s importance to have a trusted relationship with your veterinarian and patience in understanding that the timeline to recovery may be longer than desired.
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Gaschen, Frederic, DACVIM, DECVIM-CA. School of Veterinary Medicine Louisiana State University. Chronic Diarrhea in Dogs- Diagnostic Approach. 2006.
Gaschen, Frederic, DACVIM, DECVIM-CA. School of Veterinary Medicine Louisiana State University. Large Intestinal Diarrhea- Causes and Treatment. 2006.
Lidbury, Jonathan, BVMS, MRCVS, DACVIM. DVM 360. Care of Dogs with Protein Losing Enteropathy (proceedings). March 31, 2015.
Shredding, Robert G. Saunder Manuel of Small Animal Practice. Disease of the Intestines. 2006.
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