Why Do Dogs Not Get Appendicitis?

Why do dogs not get appendicitis? If you or a loved one ever developed appendicitis, you know for a fact how painful this condition is, but luckily dogs do not get appendicitis. Appendicitis is the inflammation of the appendix, a finger-like structure of the colon. When this structure gets red and angry, it causes intense abdominal pain along with nausea, vomiting and fever. While dogs may develop these symptoms as well, most likely the cause is from something else, rather than an inflamed appendix. If your dog has abdominal pain or other symptoms, please see your vet.

The Human Appendix

do dogs get appendicitis?

In humans, the appendix is a narrow, tube-shaped structure that protrudes from the cecum, a pouch-like portion at the beginning of the large intestine. The term appendix comes from the Latin word "appendix"meaning appendage, an addition at the end. For this reason, the end of a book is often referred to as the "appendix." Because of its thin shape, the appendix is also known as "vermiform appendix" fromthe Latin word "vermis" meaning worm. The appendix is located in the lower right quadrant of the abdomen and measures on average the length of the pinky, about two to four inches long.

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As useless as this structure may seem, to the extent that it's often removed by surgery without any repercussions, recent research conducted by surgeons and immunologists at Duke University Medical School, suggest that this structure functions as a reservoir for good bacteria. This cul-de-sac section of the gut, functions as a factory and “acts as a good safe house for bacteria,” says surgery professor Bill Parker, study co-author. However, Parker claims that despite its possible function, (it could turn handy in case of sudden depletion of good bacteria as can happen with cholera or amoebic dysentery) people should still have this structure removed when it becomes inflamed because it could turn deadly.

The Dog Appendix

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In dogs, the appendix doesn't get inflamed for a simple fact: it doesn't exist! While dog bodies have many similarities with the human body, the appendix is one of those exceptions. Unlike the opossum, the wombat, rabbits, great apes and other primates, dogs and several other animals do not have an appendix. Interestingly though, mammals who do not have an appendix have some other structures that, while probably not effective as the appendix, are still capable of harboring beneficial bacteria, further adds Bill Parker in an article for Duke Magazine. 

<a href="https://en.wikipedia.org/wiki/Cecum#/media/File:Cieco(anatomia).png/">Cieco</a>
Cieco by Adert, CC BY-SA 3.0

Introducing the Cecum

While some animals like the dog do not have an appendix at all, as Bill Parker mentioned, they have other structures responsible for manufacturing and storing beneficial bacteria. The cecum, which is the pouch-like structure where the appendix is attached to in humans, can turn out helpful as a safe house for probiotics should all the good bacteria be flushed away with severe diarrhea, just as the appendix in humans, claims veterinarian James C. Coghlan, in his book "Paleopet: The real reason your dog or cat eats grass."

While this digestive organ is small in the dog and not well adapted as in herbivores who rely on it greatly for fermentation purposes, it still carries some roles, even though some claim them to be minor. Symbiotic microbes live in the cecum and colon of most species, claims Dr. Lauralee Sherwood in the book "Animal Physiology: From Genes to Organisms." And while dogs have smaller cecums compared to herbivores, their cecum is somewhat larger than a cats', and according to the book: Canine and Feline Nutrition: A Resource for Companion Animal Professionals by Linda P. Case et al, that's likely because of a dog's more omnivorous nature.

Did you know? According to Vetshi, a website featuring veterinary, biological and medical science topics, meat is more readily digested compared to plant matter, which is why the intestinal system of carnivores is typically short and simple while those of herbivores is long and more complex. Since dogs though consume both meat and plant matter, their digestive system falls somewhere in between, being equipped with a working cecum that's not as well adapted as in herbivores.