Dr. Anna Dunton-Gallagher
OFF THE LEASH
It goes into their mouth as kibble, treats or a weird gelatin meat pâté, and comes out as feces. Typically, we don’t think too much about it unless we’re cleaning it up, but our pet’s gastrointestinal tract is among the most important parts of their body. Keeping it healthy and making sure they are absorbing food correctly is one of the basics of life. I’ll talk about it end to end, and things we should watch out for in the middle.
Digestion should start with chewing, but believe it or not many pets skip this step. Saliva production is an important part of both digestion and oral health, but often isn’t involved with chewing. Often we are tipped off to changes in saliva production by a drastic change in tartar accumulation. Oral health is actually more important to cardiac and renal health, but as the gateway for food, it is still an important ally in digestion. Unlike humans, dogs and cats don’t have digestive enzymes in their mouths.
This is the tube that connects the mouth to the stomach. Most of the time we don’t even think about the esophagus, but issues can arise here. Some dogs get a condition where the esophagus expands and doesn’t swallow correctly, which leads to regurgitating food. The main issue that can affect the esophagus is vomiting and the irritation that follows. Because the esophagus is difficult to reach surgically and doesn’t heal as quickly as other places, it is one reason that we often won’t have pets vomit if they ate things like scratchy bones or caustic liquids.
The stomach is one of the first places that we notice issues, because irritation leads to vomiting, which then leads to owner irritation. Stomachs add hydrochloric acid to food. This is an important part of the digestion, but excess acid can lead to reflux and stomach upset, just like in humans. Stomachs can also have ulcers, which occur more frequently with dogs on chronic medications, and especially when they get an anti-inflammatory with a steroid or aspirin. When vomiting occurs, either from the stomach or the small intestine, it can lead to more and more vomiting.
Sick stomachs need to rest, which is why we often direct pets to skip a meal once we have treated them appropriately. The stomach is a fairly stretchy organ (think Thanksgiving) but has a small outlet heading to the intestines. This is a frequent spot that things get stuck at when it is something a pet shouldn’t have eaten (rocks, toys, socks.)
Stomachs can also fill with air and cause bloating. This can resolve up to a point, but as the stomach fills with air, it can twist on itself and this can be fatal. This type of bloat, also known as “GDV” or “gastric dilation and volvulus” must be corrected surgically. It is more common in dogs with deep chests, like German Shepherds and Great Danes. It is important not to exercise your dog heavily immediately before or after feeding them, as this is a common cause.
There are three parts to the small intestine. The basic function of these areas is to digest food and absorb nutrients. When things go haywire here, we can see vomiting or diarrhea. This is why your vet may ask specific questions about what the offending excrement looked liked.
Believe it or not, we don’t ask what vomit looked like just before lunch for fun, it’s actually important. A good description can help us identify the source. This is the typical source of upset when our pets eat garbage, rotting meat or other things that upset their “stomachs.”
The small intestine is also the site of malabsorptive disorders, and areas where bacteria can take root and throw the normal “gut bacteria” out of sync. The small intestine is the culprit when pets have food allergies or inflammatory bowel disease, and is often the source of gastrointestinal cancers. Most of the lymph nodes in the abdomen surround the small intestine.
This is a very common source of diarrhea. An inflamed colon can lead to diarrhea, mucus in the stool, and even bloody stool. This is also the site of constipation. When the body is dehydrated, it pulls liquid from the colon, which can cause constipation. Ironically, when pets posture and strain it looks the same for diarrhea and constipation.
When constipation is ongoing, the colon stretches to accommodate it. It then loses some of the motility and becomes even more of an issue. This is common in cats, especially older cats with kidney issues. This must be managed early, and often for life, to make sure their colon health doesn’t deteriorate.
Two other organs which play an important part in digestion are the liver and pancreas. The gallbladder lives within the liver and sends bile into the small intestine to aid digestion. The liver also helps filter out normal waste by-products from digestion. The pancreas is the source of some digestive enzymes that help break down components of food like starches and sugars. This is also where insulin is produced. The pancreas can get inflamed, especially in dogs that have eaten a high-fat meal. Pancreatitis and hepatitis (liver inflammation) both often cause vomiting.
The gastrointestinal tract is an important and easily disturbed body system. All vomiting and diarrhea warrants a call to your veterinarian, and any that has happened more than once is a cause for a visit. Thankfully, many things can be controlled with fluids, the proper medications and GI tract rest. However, cycles of vomiting and diarrhea that are ignored or treated with the incorrect thing can self-propagate. The longer they go on, the more the body tries to compensate, and the worse your pet feels. Do them a favor and check in with your vet so that we can get them feeling better early.