Pyometra and the use of intrauterine spheres .
Keywords: sphere, marble, uterus, pyometra, lutealA 14-year-old Quarter Horse mare was presented for a chronic vaginal discharge of several months duration. Although there was a history of breeding, details of the breeding dates were unknown. Therefore a pregnancy diagnosis performed by the rDVM. This diagnosis was positive for pregnancy but was presumably not done with the assistance of ultrasonography (see below). A chronic discharge began after the pregnancy diagnosis and the rDVM and (presumably after a negative pregnancy diagnosis), the uterus was flushed with saline and intrauterine antibiotics were administered. The attending veterinarian reported that there was a mummified fetus could be palpated within the uterus. Oxytocin was ineffective in expelling this object so the case was referred to the AVC.
Transrectal ultrasonography revealed a uterus flilled with moderately echogenic fluid. This is shown below. Although pus need not be echogenic, the appearance of this uterus was consistent with most cases of pyometra in mares. The image at left, shows a cross section of a uterine horn and the image at right, the body, adjacent to the cervix (arrow).
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The pyometra was supported by a corpus luteum in the left ovary:
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The highly echogenic object seen in this video was present close to the midline. Both observers (I wish to acknowledge the assistance of my colleague Dr B. Crane on this case) were initially startled at the extremely symmetrical and highly echogenic appearance of the calvarium of the supposed "mummified fetus". Our impression was that only the head of the mummified fetus remained! However it soon became obvious that this was some other sphere-like object; possibly a marble. The reader should recall that there was no history of any insertion of a marble in this animal.
Play the video here using the built in controller or click on the link in the image. The FULL SCREEN setting is not recommended because the video has been compressed for mobility.
Prior to extraction of the object, it was noted that a pre-existig tear was present in the cervix at the seven o'clock location. The depth of the tear was approximately 2 cm caudal to cranial.
The mare was tranquilized with detomidine and analgesia was supplied with butorphanol. Over a 1 1/2 hour period, the cervix was gradually dilated using digital expansion. Then, using transrectal manipulation, the object was moved towards the cervix. A black glass sphere 3.5 cm in diameter (a "marble") was delivered through the cervix
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Following extraction of the marble, several liters of purulent material were drained from the uterus. The uterus was then flushed serially with a total of 15 L of normal saline. Ten million international units of sodium penicillin G. was instilled into the uterus and because of the presence of a corpus luteum in the right ovary, prostaglandin was administered to cause luteolysis.
The mare was discharged to the care of the referring veterinarian with instructions to re-evaluate her uterus in approximately 2 weeks and again several months later to exclude the possibility of chronic pyometra.
Notes: The use of marbles and other spherical structures has been investigated over the last 10 to 15 years in horses for the purpose of suppressing estrus in mares. The motivation behind doing so is to suppress estrus that is thought to compromise athletic performance or behavior while showing. In some cases it has be used to prevent unwanted conception. As noted by Dr A. Tibary, a similar technique has been used by Bedouin camel herders, using date pits instead of marbles.
Interestingly, the correlation between estrous behavior and
athletic ability has not been well studied and opinions are subjective at best.
This also applies to perceived links
between the estrous cycle and problem behavior. Serum progesterone samples taken during “problem”
periods of behavior have led this author to believe that many such problems
are not related to ovarian activity at all. That is not to say that they cannot
be. Indeed the author has had first-hand and unequivocal experience of this on
stud farms. However, when problems have been related to ovarian activity for
lack of a better explanation, the diagnosis must be approached with circumspect.
This is true even when the owner reports that performance or behavior has
improved after treatment because owners seek to believe that the expense or
discomfort for the mare was justified.
Most
important is that fact that it is often impossible to know if a mare is in
estrus without force teasing (nose-to-nose; nose-to-tail) or ultrasonograpy
even if her behavior on casual observation suggests otherwise. Indeed, it has
been well established that ovariectomized mares and those with inactive ovaries
can show overt signs of estrus. Also, many cases of presumed estrus-associated
behavior are reported in the winter when most mares are not cycling.
When intrauterine spheres were used, some studies have
shown that mares did not respond at all but in most studies, 40 to 75% of mares showed prolonged period of diestrus. This is because the corpus luteum fails to undergo
luteolysis. Failure of luteolysis is not a consequence of exhaustive release of prostaglandin but instead it appears to be because
prostaglandin secretion is suppressed. The reason for this is currently unknown
(2013) and is especially perplexing because most of these spheres remain in the
center of the uterus, close to the body, not migrating like conceptuses.
When a marble causes failure of luteolysis, the corpus
luteum is retained for a variable period, but usually between 60 and 90 days;
perhaps as long as 150 days in some cases. Obviously field-use of marbles is
not usually accompanied by progesterone assays or routine teasing so an
accurate estimate of the range of luteal retention is not available.
| In this case, a 35 mm glass marble was present but silver, copper or glass or water filled plastic spheres have been used as well. Smaller diameter marbles have also been used but published evidence (Nie, G.J. et al 2003) suggests that larger spheres are more effectively retained. |
Most pertinent to this case is
the fairly consistent finding in all studies that intrauterine “marbles” do not usually appear
to cause endometritis or pyometra. In a few cases, only slight fluid accumulation and mild endometritis was present. Furthermore, in one study, treated mares had normal conception rates after the spheres were
removed. Therefore, it is probably not
justified to imply that this marble was the cause of pyometra in this case. Indeed, the cervical tear in this case (and the age of the mare) probably played a greater role in the genesis of pyometra than did the intrauterine marble.
The ultrasound image of the marble lends itself to an interesting discussion on artifacts. Some of them are shown here. The pronounced acoustic interface is probably due to a gas bubble. Note the over-estimation of the size of the marble in the ultrasound image.
Image size: 637 x 450 px. With thanks to Dr Paul Rist (ACVR) pending changes
References:
- Hedberg, Y. 2006 Oestrus in the mare with emphasis on deviant behaviour and adrenal gland function Alm Acta Universitatis Agriculturae Sueciae ISSN 1652-6880 ISBN 91-576-7250-4
- Turnbull, E.B. et al. 2010 The effect of intra-uterine devices on the reproductive physiology and behaviour of pony mares. The Vet J. 186: 39–46
- Nie, G.J. 2001. Use of a Glass Ball to suppress behavioral estrus in mares Proc. AAEP 47: 246 -248
- Nie, G.J. 2003. Use of an intra-uterine glass ball protocol to extend luteal function in mares. J. Equine. Vet. Sci. 23: 266-273
- Rivera del Alamoa, M.M. et al, 2008. Mechanisms behind intrauterine device-induced luteal persistence in mares. Anim. Reprod. Sci. 107: 94–106
