Pyometra (pyo for short) is a serious and potentially fatal infection of the uterus experienced by many unspayed cats and dogs. The infection consists of a buildup of pus in the uterus. With pyometra, a normal 3-oz uterus can weigh 10-15 pounds and be filled solely with pus. At the same time, your pet's white blood cell count can go from a normal of 9,000 all the way up to 150,000-plus.
The cause of pyometra has been attributed to a dysfunction of the ovaries with increased hormonal (progesterone) secretion or by contamination of the uterus by bacteria. Sometimes it happens unexpectedly, other times it occurs a couple weeks after the heat cycle. This may be attributed to hormonal changes, or to the fact that when in heat a dog or cat's vaginal area is swollen and open, leaving it susceptible to bacteria. Bacteria grows in the moist surroundings of the vagina. Sometimes it develops into vaginitis, but if the condition worsens, it develops into full-blown pyometra.
If pyometra is undetected, neglected or left untreated, it is almost always fatal. If it is detected and diagnosed, treatment requires either the use of expensive hormonal and IV fluid therapy or an extremely difficult and expensive ovariohysterectomy—which can easily cost $600 to $1,000, depending on complications. The toxicities resulting from the infection can strain the kidneys or heart, and in some cases may be fatal or cause lifelong problems, even after the infected uterus is removed.