FrançaisWhat pyometra is and which dogs get it
Pyometra is a bacterial infection of the uterus that fills it with pus. It is generally diagnosed within 4 months after heat (estrus), in middle-aged to older unspayed females [1]. In a study of 356 bitches, all were diagnosed within 2 months of the previous heat, and the mean age was 9 years [2].
It is common. About 23–24% of insured Swedish bitches had had pyometra by 10 years of age, with a range of 10–54% depending on the breed [3]. Breeds at higher risk included the rough Collie, Rottweiler, Cavalier King Charles Spaniel, Golden Retriever, Bernese Mountain Dog and English Cocker Spaniel [3].
Signs: open and closed cervix
When the cervix is open, pus drains out as a vaginal discharge. When it is closed, the pus stays trapped. In 111 dogs, 65% had an open cervix and 35% a closed one [4]. A closed cervix was linked to more severe illness: sepsis in 77% versus 51%, and a depressed general condition in 56% versus 30% [4].
- Vaginal discharge in 76.7% of 356 bitches, so about 1 dog in 4 had none [2].
- Loss of appetite in 69.0% and lethargy or depression in 63.0% [2].
- Drinking more in 61.6% and urinating more in 59.4% [2].
- Vomiting in 21.1% and diarrhea in 15.4% [2].
- Fever in 31.9%, dehydration in 26.4%, abdominal pain in 22.7% and pale gums in 14.6% [2].
What the blood count, chemistry and urine show
| Test | What was found | What it means |
|---|---|---|
| White blood cells (WBC) | High (leukocytosis) in 54.3%; high neutrophils in 55.3% [2] | About 45% did not have a high count, so a normal WBC does not rule out pyometra |
| Band neutrophils | Present (left shift) in 14.9% [2] | Immature neutrophils, called a left shift |
| Monocytes | High in 50.7% [2] | Common: about 1 dog in 2 |
| Low white cells (leukopenia) | 3.6% [2] | Rare but serious: linked to an 18-fold higher risk of peritonitis [2] |
| Red blood cells | Anemia in 49.7% [2] | Common: about 1 dog in 2 |
| ALP (liver enzyme) | High in 37.0% [2] | More than 1 dog in 3 |
| Creatinine and BUN | High in only 4.8% and 6.5% [2] | Most dogs had kidney values in the normal range [4] |
| Albumin | Low in 81% (25 of 31 dogs) [6] | Low in most dogs tested |
| Urine | About 25% had a silent urinary infection with the same bacterium as in the uterus [2] | Urine tests can show infection even without urinary signs |
With a closed cervix, high white cells, neutrophils and monocytes were more common [4]. A closed pyometra can cause a moderate to marked rise in neutrophils, and rupture of the uterus leads to a more severe inflammatory pattern [5]. See the white blood cell count in dogs, anemia in dogs and high ALP in dogs.
Reading the white cell line on the report
A high white cell count in an unspayed female who was in heat a few weeks ago is a strong reason to look at the uterus. The opposite is also true: in one study, a low white cell count was the most important warning marker, and a normal count carried more risk than a high one [2].
- Abbreviation WBC, white blood cells or leukocytes. The differential shows which cells are increased, usually neutrophils.
- Result 28.4 × 10³/µL in this illustrative line: a clear leukocytosis.
- Unit 10³/µL, 10⁹/L or G/L: the same number in all three.
- Laboratory interval An illustrative dog interval; each laboratory sets its own.
- Flag H: above the interval. Only about half of dogs with pyometra have this flag, so a result within the interval does not rule it out [2]. A low (L) count is a warning sign [2].
How pyometra is confirmed
- History and signs: an unspayed female, a recent heat, discharge, drinking more, lethargy [4].
- Blood count and chemistry: they support the diagnosis and show how sick the dog is [2, 4].
- Ultrasound and/or X-rays: they show a fluid-filled, enlarged uterus and confirm the diagnosis [4]. See the CBC for dogs.
- Telling pyometra from a non-infected uterine condition (cystic endometrial hyperplasia): the percentage of band neutrophils was the best single test, with a sensitivity of 94%; combined with CRP, sensitivity reached 97.7% [7].
- Urinalysis: it can reveal a urinary infection, found in about 25% of dogs with pyometra [2]. See urinalysis in dogs and cats.
Outlook
Sepsis (a body-wide reaction to infection) is common: it was present in 59% of dogs in one study [4]. Even so, the outlook with prompt surgery and hospital care is good. In 356 bitches, only 1% (4 of 315) died after surgery, and peritonitis occurred in 13% of surgical cases; the authors put mortality with modern treatment at 3–4% [2]. In another study of 111 dogs, mortality was 4.5% and complications occurred in 14% [4].
Related articles
En français : le pyomètre de la chienne.
Questions to ask your veterinarian
- Does the ultrasound show a fluid-filled uterus?
- Is the cervix open or closed?
- What do the white cell count and the differential show, including band neutrophils?
- Is there anemia, and are the kidney values and albumin normal?
- Are there signs of sepsis or peritonitis, and what is the outlook for my dog?
Get your dog’s blood count and chemistry explained together.
AI DiagAnimals reads the white cell count, red cells, ALP, kidney values and albumin together with your laboratory’s intervals, and prepares the questions for your vet. The service opens soon: leave your email to be told first.
Frequently asked questions
What is a pyometra infection in dogs?
A bacterial infection that fills the uterus with pus. It affects unspayed females, usually middle-aged or older, generally within 4 months after a heat [1].
What are the first signs of pyometra?
Vaginal discharge (in about 77% of cases), loss of appetite, lethargy, and drinking and urinating more, in a female who was in heat in the previous weeks [2].
What is the survival rate for dogs with pyometra?
With surgery and modern hospital care, mortality is about 3–4%. In one large study, only 1% of dogs died after surgery [2].
Can a dog have pyometra with a normal white blood cell count?
Yes. The white cell count was high in only about 54% of cases. A low count is rare but is a warning sign of more severe disease [2].
Sources
- Hagman R. Pyometra in small animals 2.0. Vet Clin North Am Small Anim Pract. 2022;52(3):631-657. doi.org/10.1016/j.cvsm.2022.01.004
- Jitpean S et al. Outcome of pyometra in female dogs and predictors of peritonitis and prolonged postoperative hospitalization in surgically treated cases. BMC Vet Res. 2014;10:6. doi.org/10.1186/1746-6148-10-6
- Egenvall A et al. Breed risk of pyometra in insured dogs in Sweden. J Vet Intern Med. 2001;15(6):530-538. pubmed.ncbi.nlm.nih.gov/11817057
- Jitpean S et al. Closed cervix is associated with more severe illness in dogs with pyometra. BMC Vet Res. 2017;13(1):11. doi.org/10.1186/s12917-016-0924-0
- eClinPath, Cornell University College of Veterinary Medicine. Leukogram patterns. eclinpath.com/hematology/leukogram-changes/leukogram-patterns
- Jitpean S et al. Increased concentrations of serum amyloid A in dogs with sepsis caused by pyometra. BMC Vet Res. 2014;10:273. doi.org/10.1186/s12917-014-0273-9
- Fransson BA et al. C-reactive protein in the differentiation of pyometra from cystic endometrial hyperplasia/mucometra in dogs. J Am Anim Hosp Assoc. 2004;40(5):391-399. doi.org/10.5326/0400391
Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.