Old Dog Diarrhea
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Old Dog Diarrhea: Causes and Treatments for Diarrhea in Senior Dogs

The majority of pet parents of senior dogs will, at some point, encounter the same problem: old dog diarrhea. While dogs at any age can suffer from the occasional bout of diarrhea, the situation can be especially concerning when it comes to senior dogs who may be struggling with other medical issues.

There are many reasons why an older dog could potentially struggle with senior dog diarrhea. But don’t panic if, for example, your 10-year-old dog has diarrhea: Fortunately, there are several ways to address this embarrassing, messy, debilitating and often uncomfortable problem.

Types of Dog Diarrhea

First, dog diarrhea is divided into three main categories: large bowel diarrhea, small bowel diarrhea or a combination of both. The affliction is then further categorized into chronic diarrhea, acute diarrhea or intermittent diarrhea. This is important because different diseases cause different types of diarrhea, need different types of tests and require different types of treatment.

Small Bowel Diarrhea

Small bowel diarrhea develops in the small intestine. A dog who is suffering from small bowel diarrhea can have copious amounts of diarrhea a couple of times a day, but there is usually no straining or increased urge to defecate. These dogs may vomit, lose their appetite or suffer weight loss. If there is blood in the stool, it will be black or tarry-looking.

Large Bowel Diarrhea

Large bowel diarrhea comes from the large intestine, which is further down the intestinal tract, and includes the colon and rectum. In contrast to small bowel diarrhea, dogs suffering from large bowel diarrhea have increased urge to defecate and usually pass stool more often. The stool may be covered in mucus and if there is blood in the stool, it is bright red. There is usually no weight loss, vomiting or loss of appetite observed with large bowel diarrhea.

Acute vs. Chronic vs. Intermittent Diarrhea

Large or small bowel diarrhea is classified as acute if it lasts less than 2 weeks. An old dog with chronic diarrhea would suffer from the infliction for more than 2 weeks. Intermittent diarrhea can occur in the large and small bowel, and it comes and goes.

Causes of Senior Dog Diarrhea

The intestinal tract of elderly dogs can be sensitive and react poorly in many circumstances. That’s one reason why easily digestible senior dog foods—such as Nutro Ultra Senior Dry Dog Food—are a good choice for older dogs.

Learn more about the best senior dog foods here.

Old dogs often have health problems or are on medication, which can upset the balance of the body and cause diarrhea. Any disease that affects the body can also cause diarrhea.

If your old dog has diarrhea that appears to be acute and large bowel in origin, this condition is called colitis, and causes can include:

  • Eating garbage or spoiled food
  • An adverse reaction to fatty food, drugs or toxins
  • Parasites like whipworms
  • Bacterial infections
  • Inflammatory conditions like inflammatory bowel disease (IBD)
  • Irritation from passing foreign bodies
  • Irritable bowel syndrome from stress
  • Systemic illness, such as liver or kidney disease

Acute small bowel diarrhea can also be caused by the above conditions.

If your old dog has diarrhea (small or large bowel) that appears to be chronic or intermittent, causes can include:

  • Infectious diseases
  • Small intestinal dysbiosis
  • Food responsive disease
  • Inflammatory bowel disease
  • Systemic illnesses and cancer

If you know that your senior dog gets diarrhea from stressful situations like veterinary visits, vaccines or boarding, talk with your veterinarian about pre-treating your dog with probiotics, like Purina Pro Plan Veterinary Diets FortiFlora Probiotic Gastrointestinal Support Dog Supplement, to help prevent this problem.

Most cases of canine diarrhea are self-limiting, that is, nature takes its course and it clears up on its own in a day or two. If the diarrhea doesn’t clear up within 2 to 3 days, then it is time to get the veterinarian involved.

Senior Dog Diarrhea Treatment

If you notice that your dog has diarrhea all of a sudden, don’t panic! Remember that many times, diarrhea resolves on its own. You can help your dog by feeding a bland diet, such as cooked white chicken and rice or Under the Weather Rice, Chicken & Pumpkin Flavor Freeze-Dried Dog Food, for a couple of days until the diarrhea resolves.

If time and bland food aren’t curing your senior dog’s loose stool blues, it is time to get the vet involved. Before any treatment is instituted, your veterinarian will want to get a history from you, conduct a physical exam of your dog, and run some laboratory tests. Tests can include a fecal exam for parasites (bring fresh poo with you!), bloodwork and urine tests.

Treatment for the majority cases of diarrhea in older dogs includes monitoring, medication, maintaining hydration and feeding morsels that help the digestive tract.


As the pet parent, it’s your responsibility to make sure your dog eats the right food, takes all their medications and drinks adequate amounts of water. It is up to you to ensure that the recommended therapy is working, your dog is getting better and the diarrhea is resolving. Know what your dog’s normal stool, energy and appetite looks like to help you recognize when something is not right.


Medication may be prescribed to resolve the diarrhea, reduce pain and intestinal spasms and address any root causes, such as parasites or microbiome imbalances. Give all medications as prescribed and until finished, even if the diarrhea resolves before the round of medication is completed.

Maintaining Hydration

Diarrhea is a leading cause of dehydration in senior dogs. If your dog is very dehydrated, your veterinarian may give your dog subcutaneous fluids or intravenous fluids. At home, make sure to provide fresh, clean water at all times. You can also increase fluid intake by feeding canned food or adding water to dry food.

Helpful Food Morsels

Guts afflicted with diarrhea need to heal. You can help move the process along by exchanging your dog’s regular dog food for grub that’s gentler on their sensitive stomach. Think: bland, easily digestible dog food. Hill’s Prescription Diet i/d Digestive Care Low Fat Original Flavor Pate Canned Dog Food or Royal Canin Veterinary Diet Gastrointestinal Low Fat Canned Dog Food are both good dog foods for older dogs who have diarrhea, and are often prescribed by veterinarians. Feed bland food until several days after diarrhea has resolved to promote maximum healing of the gut.

If treatment does not appear to be helping your dog, let your veterinarian know right away. You may need to take your dog in for multiple rechecks and further laboratory testing or imaging studies, such as an abdominal ultrasound or X-rays, if therapy isn’t working. Patience is helpful: Just like in humans, if your dog’s gut is chronically inflamed, it can take some time and testing to figure out what is going on.

How to Tell It’s an Emergency

Reasons to take your dog to the vet immediately include:

  • Diarrhea is explosive and bloody or tarry
  • Vomiting that doesn’t stop
  • Swollen appearance to the abdomen or belly
  • Fever above 103 degrees Fahrenheit
  • Your senior dog is medically fragile due to other health conditions

If you notice that your dog develops diarrhea after taking a medication that is prescribed by your veterinarian, call your veterinarian immediately to report it and get recommendations.

Even though they sometimes need an extra dose of your tender loving care, senior dogs make wonderful companions. With the right treatment, most cases of old dog diarrhea can be resolved easily and with minimal pain.

By: Dr. Sarah Wooten, DVM, CVJ
Dr. Sarah Wooten is a practicing veterinarian, certified veterinary journalist, author, speaker, landlord, tea tavern owner, mom and warrior goddess. When it is time to play, she can be found either skiing in Colorado, diving a coral reef, or triathlon training with Team LC.