When asked for a description, I have an unfortunate tendency to compare poop to different types of food. I have been told that this is annoying, even disgusting, and that most people don’t think it’s normal. But this is an article about excrement. So, even though I promise to refrain (for this discussion only) from comparing poop to food, we will be reviewing the features of feces in a fairly descriptive way. This is your warning.
Without thinking about it, most of us know what our dog’s poop looks like. We see it, even touch it (hopefully, not bare-handed), pretty much every day, and we tend to have a good idea of what is typical. But, for the record, it should be some uniform shade of brown, moist, firm enough to hold together, but not hard or lumpy, and not so dry that it falls apart. It should be slightly glistening when it emerges and pass easily without much straining. If we see something that is different, it understandably worries us. Is this normal? Is it a problem? Will it go away? How do you know? These questions are encountered every day in a veterinary practice. So, if you’ve ever asked yourself, “What is the meaning of my dog’s poop?”—trust me, you are not alone.
I often wish I had a gift that would allow me to read dog droppings the way a fortune teller reads tea leaves. Sadly, if the skill exists, I haven’t mastered it. Instead, I think a lot about digestion, the process that brings poop into the world. If you understand how digestion works, and how different segments of a dog’s digestive tract contribute to it, you can gain a lot of insight into why a dog’s stool looks the way it does.
There are six basic components to a dog’s digestive tract: the mouth, the pharynx, the esophagus, the stomach, the small intestine and the large intestine. In this article we can ignore the first three, since, although they are vitally important, they don’t play much of a role in determining the appearance of the stool. Therefore, for this discussion, we can focus (in somewhat general terms) on the stomach, small intestine, and large intestine.
The first role of the stomach is to receive and store food so it can pass evenly and gently into the small intestine. While in the stomach food absorbs fluid, becomes softer, and is exposed to acid secretions. Dogs produce lots of stomach acid (way more than people), which begins the process of breaking down proteins, and even softening bone fragments, before the ingested material (ingesta) moves into the small intestine. The most profound disorder of the stomach that can affect the stool is bleeding. Anything that causes the stomach lining to bleed extensively— ulcers, injury, tumors—can lead to development of a black, tarry stool.
The Small Intestine
If the stomach does its job properly, the pulpy product (chyme) moves smoothly into the small intestine, the workhorse of digestion, where most nutrients get absorbed. For that to happen, the small intestine must receive enzymes and other secretions from the pancreas that help neutralize acid and break down the chyme (henceforth called digesta) into components that can be absorbed into the body. If there is a problem with this step, such as when pancreatic enzymes are inadequate, the stool sometimes appears gray with a putty consistency.
In the same area as pancreatic secretion, the small intestine receives bile from the gallbladder through the bile duct. Bile acts as an emulsifier and helps in the breakdown of fat into fatty acids that are further acted upon by pancreatic enzymes. Bile is green, but by the time it reaches the end of the digestive tract it should be unnoticeable, unless the intestine is irritated and moving the material too quickly, which can sometimes cause the feces to appear greenish. If for some reason bile does not reach the intestine, say, from a bile duct obstruction, the stool might appear orange, and possibly oily.
Because most nutrient absorption occurs in the small intestine, dogs with small intestinal problems, either from inadequate enzyme activity, or from diseases that prevent absorption of nutrients—infectious, inflammatory, cancerous—eventually begin to lose weight and look undernourished. Dogs with small intestinal disease will usually, but not always, have diarrhea, although they often defecate with normal frequency. The stool is usually foul-smelling, in part because it is not adequately processed before it reaches the large intestine.
The Large Intestine
The key functions of the large intestine are to absorb fluid and electrolytes from the remaining digesta and to prepare the newly formed stool for easy passage out of the body by lubricating it with mucus. The lining of the large intestine is highly vascular, so it bleeds easily, and when irritated it produces excess amounts of mucus. As a result, poop altered by large intestinal disease is usually somewhat gelatinous with mucus and frequently contains streaks of bright red to red-brown blood.
By supporting a population of beneficial bacteria, the large intestine also plays an important role in the breakdown of fiber, which is poorly digested in the small intestine and passes through it. When a higher-than-normal amount of digestible material makes it through the small intestine (from increased motility, poor absorption, or insufficient enzyme activity), the large intestine functions poorly, the bacteria become altered, and fermentation occurs in a way that can produce gas and odor. Changes in the gut flora also cause irritation within the large intestine, which leads to the blood and mucus scenario described above. Dogs with large intestinal diarrhea characteristically defecate with increased frequency, and usually appear to strain, even though they pass only a small amount of stool each time.
Ok, so now, hopefully, this at least partly explains why poop looks the way it does and suggests some of the changes you might see.
Why does it matter?
From a veterinarian’s viewpoint, when we first hear of any abnormality in a dog’s stool, it’s usually described as just “diarrhea.” This, of course, is not a particularly revealing description, and I’m sure some of you, at some time, have been subjected to an onslaught of probing poop questions from someone at your vet clinic. As annoying as that may be, it has a purpose. A huge part of how veterinarians respond to stool abnormalities comes from what you tell us. Diagnosing and understanding the specific cause is always ideal, but it can be challenging and often costly. If, for example, a dog has acute diarrhea (less than two weeks duration) and no other symptoms or concurrent diseases, from a practical standpoint, we may choose to simply manage the problem with medication, supplements, or changes in diet. Other cases may worry us more and call for deeper investigation. We can only make a determination if we gain some idea about where the problem originates, which means we rely heavily on your powers of observation. Speaking for myself, believe me when I tell you, I want to know everything you can tell me about your dog’s poop, and I won’t mind if you use comparisons to food in your description.
Stool Sample Basics
When you need to bring a stool sample to the veterinarian, keep these basic rules in mind:
• The fresher the poop, the better for evaluation. Poop samples should be collected within 24 hours of appointment.
• If you collect it early, you need to preserve it as best as possible, store it in the refrigerator (NOT the freezer or in the hot sun).
• Generally, a tablespoon-sized sample is fine, but always check with your veterinarian first.
• If you don’t have a fecal container from your veterinarian, an airtight plastic bag is fine — seal it, though! Clean plastic containers work well, too.
• If you are bringing a cat stool sample, make sure it is poop and not a urine clump. Clumping cat litter can make it hard to tell the difference.