The term Pyometra describes a pus filed uterus and the associated ovarian and systemic changes. Pyometra is one of the four stages of the cystic hyperplasia-pyometra complex (Dow, 1957, 58, 59). Pyometra is a serious, potentially life-threatening disorder, most commonly seen in the middle-aged diestrual (post-heat) bitch. There are two types of pyometra, open and closed. Neither should ever be taken lightly. At the onset of any symptom the bitch should be taken to the veterinarian at once. Of the two forms, open pyometra is the least severe because the cervix is open and allows drainage of the pus. In some open pyometra cases the condition has been mistakenly diagnosed as an aberrant heat. The abnormal vaginal discharge is foul smelling, of creamy consistency and tomato soup in color (although it can begin as a grayish color before turning to soup hue). The closed form has no avenue to drain since the cervix is not open, consequently the pus builds up inside the uterus, intensifying and spreading the infection until the bitch's life is in jeopardy. In the case of closed pyometra, because the uterus enlarges due to an accumulation of pus, there will be a pronounced swelling of the abdomen. As recently as 15 years ago when a bitch was confirmed with pyometra the only immediate and satisfactory resolution in order to save the bitch's life was to institute antibiotic and fluid therapies in order to stabilize and strengthen her and then surgery to remove the ovaries and uterus.

Etiology: Increased progesterone during diestrus promotes endometrial growth and glandular activity while suppressing myometrial activity. After multiple progesterone exposures (estrous cycles) the pathologic hyperplasia results in formation of cystic glands or Cystic Endometrial Hyperplasia (CEH). There is an increase in the number and size of endometrial glands, and inflammatory cell infiltrate. Hydrometra (fluid in the uterus) or mucometra (mucus in the uterus) eventually develop. Estrogen enhances the stimulatory effects of progesterone on the uterus by inducing progesterone receptors.

In particular, a pharmacological concentration of estrogen administered during diestrus greatly increases the risk of pyometra. E. coli receptors may be induced and secondary bacterial infection results. The bacteria form an antigen - antibody complexes in the glomeruli. The endotoxin from bacterial infection causes decrease in specific gravity of urine (polyuria and polydypsia). There are different theories as to the exact mechanism, but Feldman and Nelson attribute it to either an interference of sodium and chloride resorbtion in the loop of Henle or insensitivity to ADH.

1.   Ph.D Scholar, Division of Surgery
2.   Principal Scientist, Animal Reproduction Division
3.   Ph.D Scholar, Division of Medicine
4.   M.V.Sc. Scholar, Division of VPH

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