Sunday, August 7, 2011

The curse of the missing uteruses, part three

The first dog I ever tried to spay had no uterus. (She had already been spayed.) And the first cow I ever did a reproductive exam on had no uterus. (She was a freemartin.) That should be enough missing uteruses for one lifetime. But no.

On a recent shelter medicine externship, I was spaying a kitten. On this externship, you get to spay several animals every day, and I had gotten comfortable enough at it that I was hoping to get through the entire surgery without ever asking for help. To understand what I was doing, you have to understand a little about cat uteruses. Human uteruses are one big sac, probably because we tend to have just one or two babies at a time. Cat uteruses are divided into two horns, each with an ovary at the top, and the horn and ovary are attached to the body wall to hold the whole contraption in place. The horns of pregnant cats fill up with kittens, all in a row.The two horns come together at their base, where there is a little uterine body, which connects to the cervix and from there to the vagina and the outside world. To spay a cat, you cut each ovary and horn away from the body wall. Then you have loose horns, and a base which still attaches to the cervix and vagina and outside world. You cut across the base, and then you have a free uterus and a spayed cat.

So I opened this kitten up, careful to make my incision very short. Longer incisions make visualizing your work easier, but obviously are more painful for the animal, and I had just been criticized on my previous spay for making too long an incision. I used my spay hook to fish around in the abdomen, found the first uterine horn and ovary, pulled them out, and cut them away from the body wall. I traced the now-free uterine horn back to the uterine body.

Finding the first horn is hard: you dip in with the spay hook and blindly bring stuff up, mostly intestines, which you have to repeatedly shove back in until you finally get the organ you’re looking for. Finding the second horn is easy: you follow the first one back to the uterine body, and then pull the second horn out where they both split off from the base. Except in this case, I couldn’t find it. I pulled on the uterine body, which should have made the horn pop out, but no go. I pulled harder. The uterine body started to fray. Oops! I didn’t want it to break before I could find the second horn. I had a moment of indecision: I really, really wanted to get through this whole operation without asking a vet for help.  And the problem was probably just that I had made the incision too small. But I had seen too many episodes of ER in which overconfident students got into trouble in exactly this way, and if the uterus split apart before I had a chance to put a suture around it to stop any bleeding, that could potentially be dangerous for the kitten. So I called over Dr. Vine.

Dr. Vine assured me that my incision was an excellent size, and pulled on the uterine body some more. It promptly broke off in her hand. (I congratulated myself on setting her up for dealing with that situation instead of getting myself into it.) It was not a big deal, in the end: she hunted down the stump and we put some suture around it. And she said: This cat only has one uterine horn. It only has half a uterus.

Freakish! And cool. And do you know what? Cats that only have one uterine horn always, 100% of the time, have two ovaries. So if you don’t go hunt down that second ovary, they will still have heat cycles. (They won’t get pregnant, of course, but cats in heat are no fun to have around.) Dr. Vine asked me where I thought the ovary might be. I suggested, in my usual precise fashion, “Somewhere sort of near the... kidney?”

It turns out that that was exactly the answer she was looking for, because, even weirder: about 50% of cats who have only one uterine horn also have only one kidney. And this cat was one of them.

In the end, we found the ovary, just sitting there not really near anything, and we removed it. One more missing uterus for my collection, or half of one. These things come in threes, right? Does this experience count as my third missing uterus, or just two and a half?


  1. Always, 100% of the time is an overstatement about having two ovaries. Most of the time, but not always!

    Spay/neuter Veterinarian

  2. I have just had my kittens spayed and one of them only had one horn and half a uterus and one ovary. She was cut in two places, the normal place for spaying and along the bottem of her stomach for an exploratary operation to look for the other ovary but the vet couldn't find it so we don't know if she will go on heat or not.

  3. Uterus unicornis (the awesome name for "single horn uterus") is much less common in dogs than cats. I've only seen it once in a dog, and in that case I would actually have called it a hypoplastic (undersized) uterine horn, not an actually missing one. It's so rare that I called the head of that clinic over and she enthusiastically took photos for her students.

    Anyways, I have not had a more experienced vet declare to me that "even if they are missing a horn, they always have the ovary!" in dogs as I have in cats. It isn't necessarily the same mechanism so dogs could theoretically be different. But in practice it doesn't really matter -- you must hunt for the ovary no matter what! Even a tiny little ovary can release hormones, which would case your dog to cycle, which a) is annoying and b) can lead to pyometra of the remaining bits of the uterine body ("uterine stump pyometra"), which is obviously a bad thing.

    Glad your Morkie's spay was successful. Sounds like a kind of terrifying dog to put under anesthesia! Good for you for taking such good care of her :)