Clinical application of hysteroscopic hydrotubation for
unexplained infertility in the mare
Y. INOUE* and M. SEKIGUCHI
Inoue Equine Clinic, Shin-hidaka, Hokkaido, Japan.
*Correspondence email: firstname.lastname@example.org; Received: 14.03.17; Accepted: 29.10.17
Background: Therapeutic techniques for oviductal obstruction in the mare are limited. Nonsurgical and retrograde ﬂushing may be an attractive
alternative to current treatment methods for oviductal blockage.
Objectives: To evaluate hysteroscopic selective hydrotubation as a treatment option for presumptive equine oviductal blockage.
Study design: Retrospective case series.
Methods: A quantity of 10 mL of saline was ﬂushed through the oviducts in 28 standing sedated mares, which had reproductive histories of
unexplained subfertility, by inserting a catheter into the uterotubal junction under endoscopic guidance. All mares in the study had been mated through
several cycles (2–20 oestrous cycles) by known fertile stallions prior to treatment, with no evidence of conception. The average number of cycles for
each mare prior to treatment was 6.5 Æ 4.5.
Results: Saline was successfully infused into a total of 50 oviducts. Of 28 mares, 26 conceived after the treatment. The average number of cycles for
each mare to become pregnant after treatment was 1.8 Æ 0.8.
Main limitations: Diagnosis of blocked oviducts was presumptive, and pretreatment infertility was used as the control.
Conclusions: This study revealed that hysteroscopic hydrotubation using saline improved pregnancy rates in mares in which oviductal blockage was
suspected as a cause of unexplained subfertility.
Keywords: horse; oviduct; hydrotubation; hysteroscopy; infertility
The narrow papilla-like uterotubal junction is the only communication
between the lumens of the uterus and the oviduct. Furthermore, the
uterotubal junction serves as the only entrance for sperm into the oviduct
and the only route for the passage of oocytes and fertilised embryos into
oviduct in vivo is limited. In contrast, in women [1–4] and in cows [5–8], a
muscular papilla is not present at the uterotubal junction. Therefore,
diagnostic or therapeutic access to the oviduct is relatively easy in these
species. Additionally, infectious oviductal diseases, such as salpingitis,
which may be associated with infertility in mares are relatively rare
because the uterotubal junction, with its narrow entrance, may serve as a
barrier against bacteria gaining entrance into the oviduct.
Previous reports conﬁrm that collagenous masses are retained in the
ampullary–isthmicjunctioninmares[9–12]. Most masses are smaller than
the inner diameter of the oviduct and do not interfere with the passage of
fertilised ova into the uterus. However, large collagenous masses could
thus result in infertility . In addition, it was demonstrated that living
ﬁbroblast cells in the oviductal masses entered the oviduct at ovulation 
and that collagen synthesis might continue for at least a few days,
aggregating within the oviductal lumen to the extent that oviductal
transport and embryonic viability could be affected .
Techniques for diagnosis [16,17] and methods for the treatment of
oviducts presumed to be blocked with collagenous masses have reported,
and include normograde ﬂushing (via the ampulla [17–19]) or retrograde
ﬂushing (via the uterotubal junction ). For normograde ﬂushing, the
ampulla was catheterised and either a dye or microscopic ﬂuorescent
beads were infused into the ampulla, and the marker was subsequently
collected from the uterus. More recently, a gel containing prostaglandin E2
was placed over the ampulla via a laparoscopic approach to dilate the
oviductal canal and thereby enable oviductal masses to pass into the
uterus [19,21] based on evidence from Weber et al. [22,23] that embryonic
PGE2 normally dilates the oviduct to allow the embryo to pass through the
ampullary–isthmic junction. Removing larger oviductal masses via the
ampulla to isthmus approach may be difﬁcult, because the diameter of
the isthmic lumen is smaller than that of the ampulla . A retrograde
treatment for oviduct ﬂushing was reported using midline laparotomy,
which required general anaesthesia and uterine horn dissection in order to
gain access to the uterotubal junction .
A catheter cannulated into the uterotubal junction under endoscopic
guidance has been successfully used to ﬂush a stain into and through the
oviduct via hysteroscopic selective hydrotubation in 10 mares . In the
current study, this retrograde oviduct ﬂushing technique was attempted
using a ﬂexible videoendoscope in 28 mares with unexplained infertility.
Success with cannulation, pregnancy rate after treatment and
complications associated with this technique are described.
Materials and methods
Twelve maiden and 15 multiparous, barren Thoroughbred mares, and a
maiden draught mare, aged 3–20 years of age (a mean Æ s.d. average:
9.0 Æ 4.2), were enrolled in this study from 2001 to 2016 (Supplementary
Item 1). All mares had failed to conceive at multiple covers (2–20 oestrous
cycles: average 6.5 Æ 4.5 cycles) by 1–6 (average 2.2 Æ 1.4) healthy,
fertile stallions. No clinically abnormal pathology of the reproductive
organs was observed in any of the mares, and no persistent ﬂuid
accumulation in the uterus was identiﬁed pre- or post-mating. Uterine
culture, cytology and/or endometrial biopsy were performed for all mares,
and none had evidence of infectious endometritis or other ﬁndings which
could explain their failure to conceive at multiple matings. These mares
more oestrous cycles (Group 1: seven maiden and nine multiparous mares)
and those that failed to conceive at two or three oestrous cycles (Group 2:
six maiden and six multiparous mares).
The procedure was performed during oestrus (n = 25) or dioestrus (n = 3)
as previously described . Brieﬂy, with mares sedated, in stocks and
following perineal cleansing, an operator wearing a sterile surgical glove
over a long sterile sleeve inserted a 130 cm ﬂexible endoscope (Olympus,
Equine Veterinary Journal 50 (2018) 470–473 © 2017 EVJ Ltd
Equine Veterinary Journal ISSN 0425-1644