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What Causes Abnormal Dog Stool?

How familiar are you with your dog's poop? Observing its typical shape and color can help you recognize and isolate the causes of abnormal dog stool.

Melvin Peña  |  Aug 9th 2017


Did you know there are rating systems for the quality and consistency of dog stool? Becoming familiar with the normal consistency, texture and color of dog poop is one way of gauging a dog’s digestive health and recognizing when there might be a problem. There are a couple of different approaches and charts for measuring canine excrement. Popular charts issued by the Waltham Centre for Pet Nutrition and Purina describe similar ranges by shape and texture. The Waltham guide has nine categories and the Purina chart has the familiar seven-point scale.

Whether or not you use a scorecard to rate your dog’s dung, being aware of what’s normal for your dog can give you useful information to share with your vet in the event of troubling alterations, such as:

  • Diarrhea in dogs
  • Green dog poop, yellow dog poop or other unnatural dog poop colors
  • Blood in dog stool
  • Small, hard feces or constipation in dogs 

Let’s look at some of the most common causes of abnormal dog stool!

Diarrhea in dogs

Diarrhea takes a number of forms, from loose stool that emerges long and snake-like to a messy puddle, and falls under two general categories, acute and chronic. Acute diarrhea in dogs is a sudden-onset condition, meaning that there is a rapid transition from solid, well-formed feces. To some extent, regularity is a function of maintaining habits, whether that’s being acclimated to a certain diet or a certain location.

A dog straining to poop.

Healthy stool varies in appearance from dog to dog. Photography via Wikimedia Commons.

Any abrupt change in a dog’s food can lead to an episode of acute diarrhea. It is recommended that any such change be managed over the course of several days, during which the new food is combined with the old, giving the dog’s digestive system time to adjust. Anxiety can also cause fecal disruptions; a dog who is not prepared or unused to car or air travel may experience short-term diarrhea as a response to stress. In situations where food or motion is the cause, regular consistency should return within a day or two.

When a dog experiences diarrhea on a regular basis over the course of two or more weeks, it is referred to as chronic diarrhea. Chronic diarrhea in dogs may indicate a number of potentially serious health issues, including organ dysfunction, parasites, and infection. Inflammation or irritation of key organs in the digestive tract, such as the liver, pancreas, or the intestines themselves, can cause extended periods of digestive upset. Chronic diarrhea also tends to present with additional symptoms or complications, such as vomiting, fever, weight loss, or abdominal pain.

Accidentally ingesting parasites or infectious agents can lead a dog to develop chronic diarrhea, and both are key reasons to keep your dog’s food and water dishes clean at home, and to pick up after your dog when you’re out in public. One of the most common parasites involved is the single-celled Giardia, which is found where infected feces contaminate and are ingested from a range of items, from grass to drinking water. Among infectious agents, parvovirus in dogs is particularly dangerous to puppies, and largely preventable with standard combo vaccines.

Green dog poop, yellow dog poop and other weird dog stool colors

Since there are so many potential causes of both acute and chronic diarrhea in dogs, it’s worth taking special note of the relative shape or shapelessness of the feces, as well as its content and color. When dogs poop, they’re not only excreting waste products and indigestible parts of food, but also eliminating internal waste. This internal waste includes dead red blood cells, which come out in feces in the form of bilirubin. In the process of digestion and excretion, bilirubin combines with bile, giving dung its typical brown color.

A reddish dog straining to poop.

Sudden changes in dog poop color can be alarming. Photography by Joshua Ganderson on Flickr.

Discoloration in dog poop, particularly if the feces is yellow or green, can be caused by a variety of factors. Yellow stools that have a normal consistency and shape may indicate a simple short-term dietary shift. In cases like these, when things move too quickly through the digestive system to allow bilirubin to pass with feces, poop can take the yellowish tint of bile. Yellow poop can also be the result of liver, bile duct, or gallbladder problems. Green stool or dark green diarrhea may be a result of your dog eating too much grass or plant matter, or a result of ingesting a household toxin or rodenticide.

Dog pooping blood

As disconcerting as it can be to see your dog’s poop change colors, it is startling to witness an episode of hematochezia, or bloody dog stool. Here again, there is no easy answer, as the causes can range from eating a foreign object discovered in the litter bin to colon inflammation. The color of the blood can be an important indicator of the approximate area of the affliction; the more vivid the red, the more likely the source of the problem is in or near the colon. Darker, blacker blood indicates that the problem is higher in the digestive tract and has had time to be digested.

The amount of blood in the dog’s stool, as well as the relative consistency of the poop, are key signs in determining a course of action. For instance, a small streak of blood, seen once on an otherwise normally shaped piece of poop, but not afterward, could signify nothing at all. On the other hand, repeated incidents of bloody diarrhea in the course of a single day should certainly warrant a veterinary consultation. The more senior a dog, the more likely the cause is to be tumor-related; the younger the dog, the more likely the source of bleeding is parasitic.

Constipation in dogs

Any general overview of abnormal dog stool should take into account, not only degrees and colors of wet diarrhea, but also the appearance of small, hard poop. Since nearly 75 percent of normal dog poop is water, struggling to defecate, or producing dry stools with great effort, could be a result of dehydration. Dogs can become constipated by swallowing foreign objects, especially bones or hair. These items can also absorb available water and prevent normal poop formation.

A small dog straining to poop.

If abnormal dog stool lasts more than a day or two, consult a vet. Photography by Shutterstock.

Regular exercise has an impact on normal stool formation and movement through the digestive system, as does a dog’s diet. Dogs who are overfed, or exclusively fed low-quality dry kibble, may be consuming more fiber and filler than their digestive systems can process. The longer a dog excretes dry feces, or none at all, the greater the chance that constipation can turn into obstipation. Obstipation occurs when difficulty defecating causes a logjam in the colon, and unmoved feces itself causes an intestinal blockage.

Is your dog’s poop normal or not?

It might sound unappealing, even repulsive, but regularly observing and cleaning up after your dog’s poop can be both intimate and comforting. The more familiar you are with the typical appearance and texture of your dog’s feces, the more aware you’ll be when it deviates from the norm. I admit to feeling a sense of satisfaction with my dog’s diet and exercise habits, and with myself as a dog owner, when she is in a good rhythm with her pooping.

Should you notice any of these changes in your dog’s feces for more than a day or two, resist the urge to treat your dog with human medications. Before you dose your dog with something as seemingly innocuous as Pepto-Bismol, consult your veterinarian. The more detail you can provide, including when the changes started and how long they’ve persisted, the better equipped your vet will be to diagnose and treat the underlying issue.

Read more about dog poop on Dogster.com:

About the author: Melvin Peña trained as a scholar and teacher of 18th-century British literature before turning his research and writing skills to puppies and kittens. He enjoys making art, hiking, and concert-going, as well as dazzling crowds with operatic karaoke performances. He has a two-year-old female Bluetick Coonhound mix named Baby, and his online life is conveniently encapsulated here.