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7 Palpation of the Reproductive Tract

Patrick M. McCue

Equine Reproduction Laboratory, Colorado State University, USA

Introduction

Evaluation of the mare reproductive tract begins with a thorough and systematic manual palpation of the ovaries, uterus, and cervix per rectum. This may be followed by ultrasound evaluation of the reproductive tract and other procedures. Certain anatomic features such as softness of a pre‐ovulatory follicle, sensitivity of the ovary in the peri‐ovulatory period, tone in the uterus and cervix, and the presence of a parovarian cyst are easier to discern on palpation than on ultrasound.

Equipment and Supplies

Obstetrical sleeves (non‐sterile), obstetrical lubricant, N‐butylscopolammonium bromide (Buscopan®; Boehringer Ingelheim Vetmedica, Inc., St Joseph, MO, USA).

Palpation Technique

It is important that the reproductive tract be examined in a systematic manner. The specific order of the exam is not as important as consistency and thoroughness of the examination.

Administration of N‐butylscopolammonium bromide (20–60 mg IV) may be indicated to induce relaxation of the smooth muscle of the rectum and facilitate a safe palpation of the reproductive tract.

About 10–20 ml of obstetrical lubricant is applied to the palpation sleeve covering the hand and forearm. Fecal material in the rectum and distal small colon should be completely evacuated prior to manual palpation of the reproductive tract. Care should be exercised to not exert excessive focused pressure on the rectal wall to avoid rectal tears. In addition, the examiner should relax and make sure to not push forward when peristaltic contractions come over the hand and arm.

The examination may begin by evaluating the size, tone, and consistency of the cervix. The uterus is then identified and one uterine horn is palpated from the uterine bifurcation to the horn tip, and the size, tone, and consistency noted. The ipsilateral ovary can then be grasped and thoroughly evaluated. The examination is subsequently repeated on the opposite side.

In order to achieve an effective and meaningful ovarian palpation, the examiner must be able to feel all aspects of each ovary. It is significantly easier to palpate the contralateral ovary (i.e., the right ovary for a left‐handed examiner) than the ipsilateral ovary.

Any method used to hold the entire ovary that accomplishes the manual palpation examination is acceptable. One technique begins by sliding the cupped hand laterally along a uterine horn to the tip and then adjusting the open part of the hand in a cranial, lateral, and dorsal manner to contact and directly grasp the ovary (Figure 7.1).Figure 7.1 Palpation of the ovary (white arrow) as it is trapped against the pelvic wall with a hand within the rectum (black arrow) as viewed by laparoscopic camera.

If that is not successful, one can use the middle finger to “hook” the mesovarium above the ovary and use the flat part of the thumb on the caudal part of the ovary to push the ovary forward and dorsally from its location behind the mesometrium. One can then fully grasp the ovary for manual examination.

If that technique does not work, one can subsequently place the middle finger of the palpating hand caudal to the ovary and then advance the finger cranially and medially to push the ovary forward. The examiner would then pronate their hand and rotate their shoulder to grasp the ovary from below.

The goal of ovarian palpation should be to examine all aspects of the ovarian surface and ovulation fossa with gentle, firm, manual digital pressure (Figure 7.2). Follicles are recognized as smooth, dome‐shaped, fluid‐filled structures that protrude from the ovarian surface. Consistent and accurate determination of follicular diameter is important to monitor follicular growth and make sound breeding management decisions.

A mare in estrus may have one or more developing follicles on either ovary. The dominant follicle will generally increase 3–5 mm in diameter each day.

The diameter of the pre‐ovulatory follicle is influenced significantly by breed. Quarter Horse and Arabian mares typically ovulate follicles 35–45 mm in diameter, while Thoroughbred mares ovulate follicles 45–55 mm in diameter, Warmblood mares ovulate follicles 45–60 mm in diameter, and draft breed mares usually ovulate follicles 50–60 mm in diameter.

Individual mares are reasonably consistent with regard to ovulating follicles within a certain size range. However, some mares may occasionally ovulate small follicles, which can disrupt breeding plans. Initially the pre‐ovulatory follicle will be firm on palpation, but the follicle will usually soften prior to ovulation.Figure 7.2 Manual palpation of a large follicle (arrow) within an ovary.

Occasionally an examiner will feel a large follicle collapse during manual palpation per rectum. More often, ovulation is diagnosed as an absence of a pre‐existing large follicle, along with a depression in the ovary. The outer wall of the former follicle is often detectable around the boundary of the depression.

The mare may also be sensitive to manipulation of the ovary for the first 24 hours after ovulation and occasionally just prior to ovulation. Gentle digital pressure on the ovulation site may elicit a noticeable response from the mare, such as lifting the ipsilateral hind leg or a slight muscular tremor.

The lumen of the former follicle begins to fill with blood beginning 6–12 hours after ovulation, resulting in formation of the corpus hemorrhagicum (CH) (Figure 7.3). The CH may be discerned on manual palpation as a soft, spongy region in the ovary at the previous site of the large follicle.

A CH can usually be detected for 2–3 days after ovulation. Clinically, detection of a CH indicates that ovulation occurred at least 6–12 hours previously and that it may be too late to breed if the mare has not been bred already.

The mature corpus luteum of the mare is 2–3 cm in diameter and is contained within the substance of the ovary (i.e., there is no crown or papilla of luteal tissue palpable in the equine ovary) (Figure 7.4). Consequently, the mature corpus luteum cannot usually be palpated in the mare.

A parovarian cyst can be differentiated from an ovarian follicle by manual palpation of a fluid‐filled structure adjacent to, but separated from, the ovary (Figure 7.5).Figure 7.3 Corpus hemorrhagicum (arrow) within an ovary. Reproduced with permission from: Dr Anthony Claes.Figure 7.4 Corpus luteum (arrow) within an ovary.Figure 7.5 Parovarian cyst (arrow) adjacent to an ovary.

The best way to manually examine the uterus is to advance the palpation arm cranially within the rectum beyond the uterus and then retract the arm while sweeping a cupped hand in a caudal–ventral direction. It is not necessary, nor advised, to retract the equine uterus into the pelvic canal as one would when palpating a cow uterus.

Once the uterus is identified, move the cupped hand along one uterine horn in a lateral, cranial, and dorsal direction until the horn tip is reached. The uterine bifurcation is more dependent than the tips of the uterine horns. One should be able to discern uterine size, relative weight, and tone with the palm of the hand and fingertips. Repeat the evaluation on the other uterine horn.

The uterus of a mare in estrus will develop a characteristic “heavy” or “doughy” feel as an increase in estradiol stimulates the development of endometrial edema (Figure 7.6). After ovulation, progesterone produced by the corpus luteum results in enhanced muscular tone of the uterus, which takes on a “tubular” feel. With careful palpation, edematous folds may be detected within the uterine horns of an estral mare.

With the hand in the rectum to the level of the wrist, sweep the pelvic floor with a flat hand from a 3 o’clock to a 9 o’clock position, moving forward to about the mid forearm in the rectum until the tubular cervix is located. The cervix is best detected by flattening the hand and extending the fingers and pressing the cervix ventrally against the pelvic floor. The hand is moved back and forth laterally to evaluate cervical tone and length.

The cervix of a mare in estrus is usually short and relaxed (i.e., without tone) and may be difficult to identify per rectum. After ovulation, an elevation in progesterone results in an increase in tone and length of the cervix. The cervix of a mare in diestrus is typically 8–10 cm in length and 2–4 cm in diameter, running cranial to caudal and “rolls” under manual digital pressure.

The cervix of an older maiden mare may remain long and tight during estrus. Failure of cervical relaxation is one part of the “older maiden mare syndrome” that results in the retention of inflammatory fluid within the uterus after breeding. Evaluation of cervical morphology and detection of cervical relaxation failure is important when formulating a reproduction management plan for an older maiden mare.Figure 7.6 Palpation of the uterine horn using a cupped‐hand technique. Note that the uterine body has been cut open in this specimen to view the endometrium.

Additional Comments

It is important to learn manual palpation techniques and not just rely on imaging techniques, such as ultrasound, to evaluate the reproductive tract. Tactile differences in reproductive tissue may augment ultrasound findings.