What causes an enlarged Uterus?

So long story short my only 1 1/2 year old female Husky has been experiencing ongoing health issues. Started with a seizure, constant ongoing urination and thirst, multiple back to back awful heats, anxiety/ panic attacks, ongoing long term runny stool, odd smelling urine, etc etc etc. She got many tests done. A few months back ( before the previously planned spay ) she had a urinalysis done, it was very concentrated and she had high white blood cells. They tested 2 weeks after and she was fine. These issues have been going on for over a year now. Her back to back heats were awful. The last one in particular. Every time we would schedule a spay she would start another cycle quick after the previous one. The last one lasted 4-5 weeks, she bled excessive amounts one time, another time brown coloring, another day thick gooey/ chunky blood. No infection. Vet decided to risk it and spay her after this last awful heat cycle. She got spayed today. It ended up being a busy day at the clinic. A different vet ended up doing her surgery than we signed off on. I am not sure they looked around extensively as instructed. When I asked per pickup, the tech looked confused and said “ well, her organs are all there, sometimes a dog will be missing a kidney, and they are good color. “ The thing is our actual vet said they check every patient’s organs during a laparoscopic but she wanted my dog’s ( Lyric ) to be checked in depth as she worried there is a tumor causing all these issues. The tech also said the only thing off was that her uterus was very large. She did not mention anything about infection. My questions; 1, would a vet see any tumors with the simple look around of a laparoscopic spay? Or could they have missed something by not checking every nook and cranny? 2, what is your opinion on the cause? I am waiting to see if her symptoms go away now. Could it have been a hormone disorder? And 3, what causes an enlarged uterus besides pyometra ( that they didn’t mention )? Is it genetic? Could it have caused her past symptoms? She said it could have caused them, and the urinary issues/ incontinence.

Hello!   I'm pleased that your dog got speyed and hope that this settles the symptoms for her.  It sounds as though trying to have an in-depth medical conversation with a vet-tech left you frustrated.  In the UK, nurses might discharge a dog after an op; can tell you all you need to know about how to look after your pet post-op, what to look for etc. but it wouldn't be left to them to have in-dpeth conversations about the cause of your pets' disease.  If this is needed, we would advise listing your questions and arranging a conversation with the vet.    TBC.....

An enlarged uterus can be caused by infection, cancer (less likely in youngsters), polyps (fibrous lumps), inflammation, pregnancy or on old failed pregnancy, an anomaly with the formation of the uterus, hormonal irregularities etc.  It is your vets role to say what was going on in Lyric's case, but hopefully they will be able to explain what they can, up until now.  Sometimes, tumours are found on a laporoscopic spey;  certainly, the vet will be able to examine the ovaries and uterus itself when it comes out. It is also possible to miss tumours - at no moment in life can any vet tell you that your dog definitely doesn't have cancer, but if they looked and didn't see anything concerning, that's a good sign!

Here is Joe Dunne's general description of a pyometra, in case it is useful https://vethelpdirect.com/vetblog/2020/10/06/is-my-dog-at-risk-of-a-pyometra/