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I am Your Dog's Uterus

The dog's uterus plays very important roles in the intact female dog's body. This reproductive organ is similar in many ways to the uterus in women, but it's also different in many other ways. When we think of the dog's uterus, we often think about its ability to carry puppies, but since many dogs are spayed, dog owners often don't think about this organ much. Regardless, learning more about a dog's uterus can be fascinating, and in owners of intact dogs it can also be helpful so to learn how to recognize early signs of trouble that warrant a vet visit.

Introducing Your Dog's Uterus

uterus dog

Hello, it's your dog's uterus talking! Many dog owners do not deal with me much. Once puppies reach a certain age, I am removed along with the ovaries in a procedure known as "ovariohysterectomy." If that sounds a tad bit complicated, no worries, you can call it spay surgery or simply getting the dog "fixed." Those though who decide to keep me for personal choice or reproductive purposes, will probably get to know me a whole lot.

If you look at me, I am a hollow muscular organ with a Y-shaped structure. Unlike the human uterus which is like a big sac because it's mostly meant to carry one baby, I am shaped differently so the puppies are aligned nicely in a row along my uterine horns. To better understand my anatomy, take a look at the picture. The arms of the "Y" are my long uterine horns with the ovaries located at the end of each horn, the shorter part of the "Y" is my body and the very base of the "Y" is where the cervix is located. For the most part, the cervix is closed so to prevent pesky bacteria from climbing up and reaching me. In certain circumstances though such as when your dog is in heat or during birth and 3 weeks after giving birth, the sphincter of the cervix is temporarily open, explains veterinarian Margaret Root Kustritz, in the book "The Dog Breeder's Guide to Successful Breeding and Health Management."

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Did you know? There is an alternate option to spaying which involves leaving the uterus intact and only removing the dog's ovaries. The procedure is known as an "ovariectomy" and can be done through laparoscopy, a less invasive type of surgery. Not many vets offer this though.

I Carry Puppies


When dogs get pregnant, the fertilized eggs travel through the long oviducts and then descend all the way down to me where they implant and start developing into puppies. Then, once the pups are ready to be born, I will help push them out. You may think of me just as a receptacle, but I don't just sit there and carry puppies. When the puppies are in me, I have to stretch and develop along with the pups, and then once they're born, I have to return to my initial pre-pregnancy size. Call that easy!

I also help out developing the puppy's placentas, those life-sustaining structures that attach to my lining and keep the pups alive and nourished as they develop inside me. While I am mostly quiet during those 63 days of pregnancy, when the big day comes, boy do I get to work! I must contract powerfully so to open the now locked cervix and push out those pups and their placentas. Wheeeew... that's quite a task! My job is still not done though, my contractions must continue even after all that work so to stop that annoying post-partum bleeding and get rid of any excess fluids.

Did you know? Once an ovum is fertilized, it's known as a "zygote " and by the time the zygote is ready to implant in the uterus lining, it's known as a blastocyst. 

When Things Go Wrong

dog pain goes away at the vet

Even though I am quite a simple structure, I am prone to several problems. When vets remove me during a spay surgery, sometimes things can go wrong. When it's time to give birth, I may encounter some difficulties. Also, as I age and go through several heat cycles, I am more likely to thicken and become vulnerable to problems. Unlike humans though, dogs do not go through menopause, (yes, no doggy hot flashes!) so hormones keep being produced even into old age.

Surgical Complications

When a dog is in heat, I can become enlarged compared to a dog who is not in heat. If you are planning to spay your dog and your dog is in heat, expect veterinary receptionists to give you a bit of a hard time. Things get more complicated when I am swollen. This is why vets recommend waiting or charge more for spaying a dog who is in heat than one who is not.

While a spay surgery is really routine surgery, sometimes, in rare cases, things can get a bit messed up. Some of my tissue may be left behind and this can create problems. When this happens, the dog can't bleed or get pregnant, but she may still develop others signs of a heat cycle, explains veterinarian Chris Bern. Deja vu, anyone? When this happens, it's known as Ovarian Remnant Syndrome in Dogs. In some rare instance, these ovarian and uterine tissue remnants can develop what is known as "stump pyometra."

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Hormonal Abnormalities


When a dog is left intact (not spayed), there are risks that I can get infected at one time or another, especially in dogs over the age of six. Here's what happens. As dogs go through several heat cycles without getting pregnant, my lining tends to thicken and cysts that release fluids may form. Now, consider that progesterone levels stay high for about 2 months following heat regardless if the dog is pregnant or not (that's why it's so hard telling a real pregnancy from a false pregnancy). These high levels of progesterone inhibit my muscles from contracting and expelling bacteria, thus creating the perfect grounds for a secondary bacterial infection.

This is when dogs get in trouble and develop what is known as pyometra, a condition that happens about two to eight weeks after the heat cycle. If the cervix is open, pus will drain out from me and make its way outside. This is when dog owners notice the abnormal discharge under the tail. If the cervix is closed, the pus will not have an outlet, thus it will collect in the dog's abdomen causing it to enlarge and be very painful. Due to all the fluid accumulating in me and diseased tissues, I may go from weighing just a few pounds (as seen in an average-sized dog) to weighing even up to four pounds, warns Dr. Becker! No wonder why people have compared me to a stuffed venison sausage when this happens! With all this trouble going on, affected dogs get severely ill very rapidly, drinking more, acting lethargic and sometimes vomiting or having diarrhea. But wait, the worse has to come...If treatment isn't sought quickly, I risk rupturing, spilling out my contents into the abdomen which can result in a fatal septic peritonitis or acute kidney failure. Yes, you don't want to mess with me when I get so sick, see your vet at once!

"In the past, we thought pyometra was simply a uterine infection, but today, we know that it is a hormonal abnormality, and a secondary bacterial infection may or may not be present."~Dr. Marty Smith

Bacterial Infections

Remember how I said that the cervix is usually closed, but during a heat cycle or after giving birth it tends to remain open? Well hear me out.. During a dog's heat, the cervix is open so to allow sperm to go through, but along with the sperm, bacteria may make its way up to me. After the heat, the cervix tightly closes, trapping the bacteria inside. When bacteria invades me, dogs develop what is known as "metritis." How is metritis different from pyometra? Unlike pyometra, metritis is not caused by a hormonal abnormality. Also, metritis is likely to develop right after the dog gives birth and sometimes after abortion or breeding, explains veterinarian Dr. Bari Spielman. I often get infected when right after birth there are retained placentas or dead fetuses. Now you know why most vets recommend a check up the first 24-48 hours after your dog gives birth.

Uterine Inertia


Sometimes, for one reason or another, I may get sluggish, and unable to contract enough to push the puppies out. When I act this way, you know you have to get help as fast as you can as I can't perform my pushing duties. What causes me to not contract as I should? Dr. Lopate a member of the American College of Theriogenologists explains in the book "Management of Pregnant and Neonatal Dogs, Cats, and Exotic Pets" that this can be due malnutrition or conditions such as hypocalcemia, fatigue or some other systemic disease. When I fail to contract with sufficient force, the condition is known as primary inertia; whereas, in secondary intertia, my contractions are first vigorous but then they decrease in vigor. Often the problem is due to how the puppy is positioned, or if the puppy is too large and the birth passage to narrow. That's the price to pay for those breeds with large heads! At the first signs of trouble, your best bet is to touch basis with your vet. Your vet may give your dog a shot to jump start me and get me back to work or he may need to do a C-section.

As seen, I am more than just a receptacle that holds puppies until they are born, I perform quite some complex roles. If you own an intact female, it's imperative that you contact your vet as soon as possible at the first signs of trouble with me. And if your dog is pregnant and nearing delivery, please do me a big, big favor, will you? Keep your vet's phone number handy, and get help as soon as you can so that I can do my work and safely deliver that batch of puppies you have been waiting for. Your dog, the pups and me will thank you.

Respectfully yours,

Your Dog's Uterus.

Dog Pawprint

Disclaimer: this article is not to be used as a substitute for professional veterinary advice. If your dog is having health problems, please consult with your vet at once.


  • Pet Place, Structure and Function of the Female Canine Reproductive Tract, retrieved from the web on May 2nd, 2013
  • Pet Education, Anatomy and Function of the Reproductive System in Dogs, by Dr. Race Foster, retrieved from the web on May 2nd, 2013
  • VCA Animal Hospital, Pyometra in Dogs, retrieved from the web on May 2nd, 2013
  • Management of Pregnant and Neonatal Dogs, Cats, and Exotic Pets, By Cheryl Lopate, Wiley-Blackwell; 1 edition (13 July 2012)
  • Clinical Anatomy and Physiology for Veterinary Technicians, 3e3rd Edition by Thomas P. Colville DVM MSc (Author), Joanna M. Bassert VMD (Author), Mosby; 3 edition (April 2, 2015)

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