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Monday, March 24, 2014

Pyometra in a 5 year Newfoundland bitch.

Keywords : canine, pyometra, uterus, luteal, progesterone

A five year old nulliparous Newfoundland bitch was submitted approximately 30 days after the end of  estrus with a history of PU/PD of one week duration. The day before submission, a hemorrhagic-purulent was seen. On presentation, the patient was febrile (39.8 deg C) but was bright, alert and responsive.

CBC showed a mild neutrophilia (21 x 10/9 per ml) with a moderate left shift (26% bands) and mild monocytosis.  There was also a mild non-regenerative, normocytic and normochromic anemia.  Serum chemistry values were within normal limits. Interestingly, despite reports of PU/PD, urine values (including SG) were normal. A diagnosis of pyometra was made and an ovariohysterectomy was performed. Culture of the uterine contents revealed a pure growth of  hemolytic E coliThe bitch was treated with 1500 mg cephalexin p.o. b.i.d for 14 days. Recovery was uneventful.

Macroscopically. the uterine horns and body were symmetrically distended by large amounts of malodorous, thick, red-brown, cloudy exudate. Macroscopic evaluation of a cross section prepared for histology appeared as follows.



Image size: 776 x 960px. 

Even at this magnification, dilation of the endometrial glands was remarkable. For comparison, the histology of a normal bitch is shown below.


Image size: 856 x 468px. Copyright: unknown. Please contact Dr Rob Lofstedt (lofstedt@upei.ca) if you hold copyright for this image.

Patchy reddish brown areas of hemorrhage were present on the endometrial surfaces. One such area is shown below. These accounted for the hemorrhagic appearance of the vulva discharge. 




Comment by Dr Donald Schlafer. Don Schlafer DVM, MS, PhD DACVP, DACVM, DACVM 
Professor of Theriogenologic Pathology, Cornell:

"The tissues in the photomicrograph in the case have characteristic features of pseudo-placentational endometrial hyperplasia (PEH). The endometrial changes is this form of endometrial hyperplasia develop in a highly organized manner and bear a striking resemblance to remodeling changes that occur in the endometrium of  pregnant bitches in the area beneath the placental labyrinth.
Microscopic features of PEH resemble those found at normal canine placental sites but no fetal tissues or labyrinth is present.
In the photomicrograph above, one can see that there is a very uniform band of cystic segments of the deeper portions of  endometrial glands. This band goes all the way around the endometrium. Note the uniform the size of the distended deep gland segment. In contradistinction, the endometrial glandular cysts of classic CEH vary in size, location and number within the endometrium. 
 For addtional detail see: 
Schlafer, D.H. 2012. Diseases of the Canine Uterus. Reprod Domest Anim. Suppl 6:318-22
McEntee, K. 1990. Reproductive Pathology of Domestic Mammals ISBN-10: 0124833756. See photomicrograph, Fig 11.6, p174
Jubb, Kennedy & Palmer's Pathology of Domestic Animals 2007. ISBN: 978-0-7020-2786-4 Volume 3. Chapter 4. The female genital system.  (p463)"

Microscopically, the epithelial lining of the uterus was extensively eroded in this case. The lumen contained large amounts of cell debris, degenerate neutrophils, proteinaceous debris, variable amounts of erythrocytes and myriads of small fine bacilli.



Image size: 1205 x 584px.

The endometrium was diffusely moderately thickened due to the presence of many variably sized, often cystically dilated glands. Some of these were filled with pale to dark, pink proteinaceous secretion.


Image size: 1205 x 716px.

Although the cell populations in the gland were dominated by neutrophils, large populations of plasma cells predominated in the interstitial tissue. In the images above and below, plasma cells are those with dark nuclei and strongly basophilic cytoplasm. 

In the image below, the relative tissue distribution of plasma cells and neutrophils is obvious.


Image size: 1200 x 588px.

There were at least three corpora lutea in both ovaries combined; the exact number was not recorded.



Notes: 
1. Pyometra in bitches has been well described. As in this case, pyometra usually occurs during the 60 to 65 day luteal phase following ovulation or shortly afterwards. It is age related, occurring mostly in bitches older than four years and typically those that are nulliparous.  

Quoting from a review of the subject ( Smith, F.O. 2006. Canine pyometra. Theriogenology. 66: 610–612) "The pathogenesis of pyometra in the bitch involves estrogen stimulation of the uterus, followed by prolonged intervals of progesterone dominance. Progesterone results in endometrial proliferation and uterine glandular secretions and decreased myometrial contractions. Leukocyte inhibition in the progesterone-primed uterus often supports bacterial growth. These effects are cumulative, with each estrous cycle exacerbating the uterine pathology."

In that quote ".....endometrial proliferation and uterine glandular secretions" causes the phenomenon known as cystic endometrial hyperplasia (CEH). CEH was striking in this case.

2. Unfortunately vaginal cytology is seldom routine in the diagnosis of pyometra. Therefore clinicians often refer to cases of pyometra being either "closed" or "open" on the basis of overt purulent discharges. In fact, vaginal cytology will reveal that few cases are indeed "closed"; a finding that would change treatment options in some cases. Even if the pyometra is closed, safe non-surgical options for treatment now exist, especially in countries where the progesterone receptor site antagonist, aglepristone, is widely available.

The author appreciates and acknowledges the assistance of Dr David Sims AVC. sims@upei.ca in the histological photography of this case.