Ovarian Cysts and Their Impact on Bitch Fertility

In February of 1997, I wanted to breed my Boxer bitch, Bitwyn's Shadow Fox. She had produced a very nice litter the first time she was bred--including a dog who went on to become a Top Twenty competitor this year. Unfortunately, she had come into heat near the end of January and Westminster week interfered with what I estimated to be the ideal time to breed. After we returned from Westminster, she was still acting very receptive so I had a progesterone test and a vaginal smear done to see if there was any chance that it might not be too late to breed her. I was delighted to be told the results of the progesterone test indicated that she was actually in "late proesterous." And the following weekend would be the best time to breed according to the test results. The results of the vaginal smear however were more uncertain, but my Vet felt we should trust the "progesterone test since it was known to be more accurate than vaginal smears." Based on the progesterone test results I decided to do the breeding--even though it was her 18th and 20th days according to my calculations.

Needless to say, the breeding wasn't successful even though my bitch stood for the dog and accepted him. She is a very affectionate and playful bitch, and it was a good first experience for the young dog to whom she was bred. There was nothing in her own behavior that indicated any problem with the results of the progesterone test. And she gave me further hope that it was successful by going into a full blown false pregnancy. When enough time had passed to do an ultrasound, I had one done partly because I had noticed a few spots of blood discharging from her vulva. I was very disappointed to find there were no puppies, although I should not have been surprised because the "timing" of the breedings was way off according to my own calculations.

Shortly after the negative ultrasound, she appeared to be coming in season again. This was very disturbing because she is normally on a seven and half month cycle and barely two months had passed since she was bred. I had further tests done and was amazed to find that according to the progesterone test, she was still in "late proesterous" two months later. One of the tests performed by my Vet was another obstetrical ultrasound--but with the emphasis on the ovaries rather than the uterus. We wanted to see if there was any irregularity that could account for the strange readings we were getting on the blood work, including the latest set of progesterone tests. Nothing significant showed up on the ultrasound but clearly something was wrong.

At this point, I became very concerned and upon the recommendation of my own vet, took her to Dr. Katrin Hinrichs, a Theriologist (reproductive specialist) at Tufts University Veterinary School in North Grafton, Massachusetts. I have loved and lived through the treatment of another Boxer who suffered from cancer, and as any of us would under these circumstances, my first fear was that Vixen had cancer.

After extensive testing at Tufts Veterinary School, we discovered, by the use of their extremely powerful, state-of-the-art ultrasound machine, that Vixen had a very tiny ovarian cyst (about the size of the head of a pin) in one of her ovaries just beneath the surface of the ovary. The cyst was too small to have been detected by my regular vet's ultrasound machine--which simply wasn't powerful enough to achieve the resolution needed to find the cyst. Here is the diagnosis from Tufts Veterinary School Hospital on 4/8/97:

"Vulvar bleeding without estrogenic stimulation. Vixen was bred on 2/15/97 and 2/17/97. Ultrasound for pregnancy on 3/ 29/97 showed she was not pregnant. Intermittent slight bloody discharge was noted starting 3/28/97.

A vaginal smear done today showed a typical non-estrus smear, indicating that Vixen probably doesn't have estrogen stimulation. A blood sample was drawn to measure progesterone levels; if Vixen was in a true heat in February the progesterone should be high

Ultrasound revealed a small cystic structure within her right ovary although the ovary was of normal size. The left ovary looked normal. No fluid was noted within her uterus and no tumor-like structures were noted.

If Vixen's progesterone level is high, this would indicate that this cyst is insignificant amd should not be treated. If her progesterone levels are low however, we should consider treating the cyst with hcG (human chorinic gonadotrophin) which acts like luteninizing hormone (LH) to cause the cyst to mature and eventually disappear.

A vaginonscopy was performed under sedation and no abnormalities were found, such as foreign bodies or masses that could explain the vulvar bleeding. According to test results the progesterone level is low."

Dr. Hinrichs suggested a series of hormone shots to attempt to have the cyst act like an ovum and erupt--without having to resort to surgery on my bitch. She also requested that Vixen be tested for Cushing's disease (a thyroid related disorder). The test was done and Vixen was found to be free of Cushings and a thyroid profile was also done on 4/23/97 and her thyroid showed normal.

"Specimen: Serum Results Normal Range

Total Thyroxine (TT4) 17 (15-50) nmol/L

Total Triiodothyronine (TT3) 1.8 (1.0-2.5) nmol/L

Free (Unbound) T4 (FT4) 18 (12-33) pmol/L

Free (Unbound) T3 (FT3) 00 Quantity insufficient to test

T4 Autoantibody 00 Quantity insufficient

T3 Autoantibody 00 Quantity insufficient

Thyroid Stimulating Hormone 11 (2-30) mU/L."

Dr. Hinrichs believed that because the cyst was so small, it was not stopping her reproductive cycles completely but was interfering with the normal hormone cycle she should have been experiencing. If the hormone shots didn't work, we could go in and remove the affected ovary--which should allow her one remaining ovary to function normally. Naturally, I hoped to avoid this option and its increased risk to Vixen.

To understand what was happening to my bitch, it is important to know exactly how a normal bitch's reproductive cycle works and how the cyst was impacting Vixen's cycle. A bitch's heat cycle (or estrus) usually lasts 21 days. The first part of the cycle is called proestrus. It is usually characterized by dark bloody discharge and the noticeable swelling of the vulva. Normally proestrus will last between 6 and 9 days, depending upon the individual bitch. The second stage of the heat cycle is called estrus (or standing heat) and is the period when the bitch will accept the male. Usually this is characterized by a softening of the vulva and a change in the color of the discharge from dark red to pinkish. The final stage, called metestrus begins when the bitch refuses to stand for the male and continues for a period between 60 and 105 days during which the uterus repairs itself. At the end of metestrus, the anestrus period begins (this is the "interheat" period) and, depending upon the individual bitch, will last from 100 to 150 days.

A bitch's reproductive cycle is governed by hormones released by the pituitary gland. The heat starts when the pituitary gland releases FSH (follicle stimulating hormone). This hormone causes the immature egg cell follicle in the ovary to begin to mature. As this happens, the follicle releases estrogen, which causes the change in the bitch's behavior and the secondary sex symptoms (like the bloody discharge and the swelling of the vulva). Another pituitary hormone called LH (luteninizing hormone) causes the maturing egg cell follicle to rupture and release the egg cells (ova) into the bitch's fallopian tubes. Ova must have another 72 hours in the fallopian tubes in which to complete the maturation process and become fully fertile. During the early part of this process, other hormones like progesterone normally are at lower levels. However, if there is an excess of progesterone present, it will block the production of FSH and the heat cycle will be aborted.

As the egg cell matures, it produces less estrogen and gradually increases the production of progesterone. It is the progesterone which causes the vulva to become soft and pliant during late proestrus and allows a fertilized ova to implant in the uterine lining. Excess estrogen at this point will block the preparation of the uterine lining--a shot of estrogen given within 7 days of a mating will prevent the implantation of the fertilized ova (the mis-mate shot). The used egg follicle (after the release of the egg cells) becomes a small cyst like structure called the corpus lutenem. It's function is to continue the production of progesterone which is necessary to support the pregnancy. Without adequate progesterone, pregnancy is impossible and an abortion will result. Eventually, the corpus lutenem itself dissolves (if there was no mating) and the anestrus period begins. However, if the ovaries become cystic, they will continue to produce estrogen and keep a bitch in season for much longer than is normal. A normal reproductive cycle depends heavily upon the right progression of hormones and the timing of their release--if the hormone cycle is "out of order", normal heats and normal fertility will not occur.

During these tests and procedures, Vixen appeared to be in season again. It did not appear to be normal season but I would have liked to breed her if the hormone shots were successful. There is a great deal of reliance on progesterone testing to pin point the ideal time to breed bitches. I have been informed on several occasions that these tests are much more reliable than a vaginal smear. In vixen's situation however, the vaginal smears I had done were a more reliable indicator of her condition than the progesterone tests. Initially, the hormone shots did not appear to work, although my own Vet wasn't able to detect the cyst, it still showed up on an ultrasound done on Tufts' more powerful machine.

About a year later, another ultrasound by my own Vet again showed no trace of the cyst, but more important to me, she had an apparently normal heat cycle since the original incident and had come into heat again with what appeared to be another normal heat cycle. Because she was now six years old and I hoped to breed her one more time, I arranged a breeding on the second "normal" season--which was successful. By breeding her at what I calculated would be the correct time and by relying on the vaginal smears as well as progesterone tests, she became pregnant and delivered a small but healthy litter of two puppies on May 24, 1998. It is my belief that the size of her second litter was probably due to the fact that she still retained the cyst, first discovered in the Spring of 1997. Her other ovary functioned normally--which made it possible for Vixen to become pregnant and whelp healthy puppies when bred at the proper time but she only had two puppies because her cystic ovary still wasn't functioning correctly, in my opinion. Because of this and her age and the high incidence of cancer in Boxers and the fact that she went into uterine inertia with her second litter, it was necessary to have them delivered by cesarean section. I had Vixen spayed at the same time to prevent any further problems from developing.

After the experience I had with the progesterone tests with Vixen in February of 1997, I don't personally have all that much confidence in them. The vaginal smears that I had also had done turned out to have been much more accurate (in Vixen's case) than the progesterone test and if I had based my original decision on the vaginal smear results rather than the progesterone test results, I never would have bred her when the problem first occurred in February of 1997. My point is that progesterone tests are not 100% accurate and can give false readings, so it might be a good idea to have your bitch checked by a reproductive specialist (if there is one in your area) before making any decisions on breeding, if you have been experiencing problems in getting a bitch to become pregnant.

The unerupted cyst which may have started its "life" as a regular egg cell that, for some reason, never matured properly and became encapsulated and cystic instead of being shed from her ovary, had a profound effect on Vixen's reproductive cycle. It is also possible, in my opinion, that an incident like this could be the basis for the development of an ovarian tumor. It might be a good procedure for every breeder, who is able to do so, to have a "complete" gynecological work-up done by a reproductive specialist on their bitches over the age of five--if they are intended to be used for breeding again. Obviously it also makes sense to spay every bitch who will not be used for breeding again as soon as possible. While this won't diminish the chances of mammary cancer, it will certainly eliminate any chance of ovarian or uterine cancer from developing in our older bitches.

by Liz Sullivan
From the ABC News Bulletin
September 1998

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