Equine transrectal palpation
Keywords: caution, equine, palpation, rectum, diagnosisTransrectal palpation is commonly used to examine the abdominal contents in horses; in this case, the genital tract. It is usually practiced by veterinarians and animal scientists. It is not for the untrained. Transrectal palpation is also referred to as rectal, or recto-genital palpation. The author spent much of his professional career in the United States, where litigation is more common than elsewhere. During those years, rectal tears were a common cause of lawsuits against veterinarians; second only to epistaxis caused by nasal tubing. The author served as a specialist witness for the AVMA in these cases and learned first hand of the errors that led to lawsuits.
Every operator has her/his personal preferences for transrectal palpation. Despite the potential for litigation in this regard, there are few specific standards for transrectal palpation from auspicious associations such as the AVMA and AAEP. In this entry, the author draws on more than 40 years of personal experience in equine reproduction to provide specific guidance and a personal perspective on the subject.
The image below shows the appearance of equine transrectal palpation under optimal conditions .
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The grey bin is for feces and excess lubricant; a potential slipping hazard. Also note the red glove; not optimal in the author's opinion because it can disguise traces of blood. Unfortunately, gloves for transrectal palpation are seldom available in sizes for those with small hands (a marketing opportunity!). The operator's sleeves are rolled up or removed.
In many cases, conditions are not optimal. The author has performed transrectal palpation in open fields, free standing in stalls, in mares restrained with only-cross ties and so on. On one notable occasion a rambunctious mare was examined free-standing, in a open field in Mexico with restraint provided by several tough rancheros, discussion football scores. Ultrasound was performed with the unit in a cardboard box to shade its screen. These were all interesting experiences but in retrospect, foolhardy. Rectal tears are often fatal in mares.
On stud farms, or where large numbers of horses housed, owners should be strongly encouraged to build stocks for the numerous examinations performed on horses.
The author believes that stocks are often too wide for horses. To prevent side-to side-movement, stocks should not be much wider than 27 inches (69 cm); perhaps 30 (76) at the most. A 27 inch wide set of stocks will even accommodate most draft mares.
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If the stocks are too wide, the head of the mare should be drawn to the side of the stocks opposite the person examining the mare. This is illustrated above by the green saggital line and the large green arrow at the hind quarters. The small green arrow shows the position of a rope in front of the chest of the mare. This used to keep the mare close to the back of the stocks, close to the operator. In essence, the mare's hind quarters should always be as close to the operator as possible. In that manner, the potential for kicking injury (rare) to the operator is minimized. In this case a rope is being used behind the mare as well. All ropes should be tied with quick release knots.
When there are no stocks for palpation, the operator should back the mare up to just outside the stall door and stand so that the arm used for palpation is unlikely to be injured if the mare moves sideways (see the red ring in the image below).
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In this case, the mare has no chest restraint so she must be prevented from moving forward by the handler alone. Sudden forward movement can result in rectal tears when the operator is grasping an object through the rectal wall at that time. Twitching or tranquilizing may be required (for the mare, not the operator!) in a few cases. The use of hobbles should not even be contemplated; a single experience of a horse, down and struggling in hobbles will convince one of that. Finally, there should be constant communication between the operator and the handler; exchanges on football scores and failed marriages should not be part of the discussion.
Having retired recently, the author can now safely say that he has never been seriously injured while examining a mare. As for personal safety, it is his preference not to have a solid door behind the mare for these examinations. Guillotine-like injuries to his left arm have led him to that conviction. Instead, a rope is placed behind the mare, to prevent a stray hoof from going much beyond the back of the stall.
Neophytes should be aware that very few mares plan to annihilate the operator. Indeed, most will submit to transrectal examination without resistance. Unlike cattle, most mares also have obvious body language. If a mare has her ears pinned back and is obviously restless, indifference to those signs, followed by a quick "goosing" entry into the rectum can spell disaster. The worst operators and those at greatest risk, are guided by bravado. Inexperienced veterinarians should also be aware that owners (and even more unfortunately, colleagues) may place pressure on them to perform transrectal examinations under dangerous conditions. The author knows of cases where this has not only resulted in severe injury, but death. Operators should resist such pressure, even if it is perceived as losing face. Going ahead may indeed cause one to lose face!
The actual technique:
After the mare is restrained, a tail wrap should be applied to prevent hairs from entering the anus. Even this is considered superfluous by some, it is at least, professional in appearance. The author is shown here keeping his face to one side, lifting a mare's tail and slowly introducing one finger, then several and then a whole hand into her anus. Copious lubrication is essential.
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As the mare relaxes, one can gradually move in behind her.
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Incidentally, the author was wearing rubber boots for the purpose of these photographs. Bovine practitioners would not give this a second thought but those who spend time around horses realize this as being unsuitable. A fine haircut is optional.
During transrectal palpation one should glance up frequently to check the mare's body language, especially the lay of her ears (high-lited above). For many years. the author was blessed with an excellent technician who watched mares carefully during these examinations.
As mentioned, copious lubrication is essential. Equine feces are dry in comparison to those of cattle. A single bottle of lubricant may suffice for a 100 cows; for mares, perhaps two or three. The rectum is cleared of feces and palpation begins. See video.
In the video and all subsequent images, the rectum has been removed. In reality, the rectum forms a glove around the operator's hand. After some experience, this becomes subconscious and one does not even consider the fact that one is actually palpating through the rectal wall. In some cases however, rectal tone makes this patently obvious. in such cases, butylscopamine (Buscopan® a parasympatholytic agent, can be used to make palpation safer and more accurate.
The first image shows the uterus and ovaries suspended from the dorsal body wall by the mesometrial/mesovarian ligaments. The normal orientation of the ovarian fossae i.e. ventral and lateral ("down and out", like a poor soul on skid row) can be appreciated in this image. Naturally, that is where the infundibulim lies as well. This illustration also shows the position of the uterine artery; in the mesometrium, just to the right of the operators fingertips. This significance of this is discussed elsewhere in LORI.
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In most cases, the cranial margin of the uterus can be defined easily because it is the only palpable structure that runs transverse to the saggital plane and is this far caudal in the abdomen. The operator may have to guide the hand down at perhaps, a 30 degree angle with the elbow reaching the level of the anus before the cranial margin can be grasped. Obviously this varies with the size of the mare and the operator. This brings to mind the story of our late, diminutive but auspicious college Dr Marcel Vandeplassche in Ghent, Belgium. On tip-toe, he was examining a huge Belgian mare and with the length of his arm and some shoulder no longer visible, when the owner (wide-eyed and only half joking) asked him if he was planning to climb inside.
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Once the operator has defined the cranial margin of the uterus, three or four fingers are hooked over it and the hand is moved from side to side until a clear, three dimensional image has formed in the mind of the operator.
The author suggests that one should not leap to the anticipated position of the ovaries until the uterus has been palpated in its entirety. This is because the ovaries may be difficult to locate without knowing the full extent of the uterus. The sector of palpable structures (dictated by rectal tone) usually means that the operator's hand leaves the uterus some distance before reaching its tip. Therefore one does not detect the ovaries where one would anticipate them to be, in relationship to the uterus. They are usually palpable more cranial to this. This may also occur because one moves the ovaries cranially with one's advancing "rectal glove". After reaching the cranial-most palpable extend of the uterus, the operator may have to make a small "leap of faith" cranially, dorsally and laterally to grasp an ovary. It may also be helpful to pull gently on the tip of a uterine horn for several seconds then release it. This will often make it possible to palpate the ovary on that side.
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In many cases, rectal tone prevents accurate palpation of the ovary; another distinct difference between cattle and horses. As mentioned, parasympatholytics can assist one in defining ovarian structures with greater accuracy than otherwise. Even so, certain structures, such as the ovarian bursa, remain impossible to examine by transrectal palpation in mares. By contrast, in cooperative cattle, this is certainly possible.
Once grasped, the characteristics of an ovary are unmistakable. It far larger than in cattle, it is firm and has a well-defined ovulation fossa (absent in cattle). It may contain small or large follicles, 5 cm or more in diameter but because of the presence of a confining tunica albuginea (also absent in cattle) it is impossible to determine their size accurately. One can only do this by using transrectal ultrasonography. Another difference between horses and cattle is that corpora lutea cannot be detected by transrectal palpation in horses. In the absence of ultrasonography therefore, it is impossible to determine if a mare is having estrous cycles.
A complete discussion of pregnancy is beyond the scope of this entry.
It has already been mentioned that there is considerable cervical tone during pregnancy but that fact is worthy of repetition. The cervix may be so firm and narrow (resembling a thin finger) that an inexperienced operator has trouble believing that it is indeed the cervix. This tone is palpable even as early as 14 to 15 days after ovulation. Uterine tone is also remarkable during early pregnancy. Therefore pregnant mares are excellent subjects for experienced operators to examine. This convinces them that the uterus is indeed palpable!
The tongue-in-cheek image shown below can be used to illustrate the characteristics of a pregnant uterus to veterinary students. The cervix feels like a hard finger and the uterus, like a sausage! The two black objects in the left uterine horn represent two embryos. The inset at upper left shows the side-to-side manner of palpating the uterus.
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After the uterus and ovaries have been examined by transrectal palpation, the tract is examined by ultrasonography.
When a ultrasound transducer is held in one's hand, it is not possible to palpate efficiently. Therefore ultrasonography should not be performed before a three dimensional mental image of the tract has been formed in the mind of the operator, using transrectal palpation. After the features of the tract have been mentally assembled, one can examine those features using ultrasonography. Mistakenly, an inexperienced operator may believe that the process is best done in reverse, using ultrasonography first because of one's ability to:"see the structures". If this is done, it is likely that sections of the tract will be examined incompletely or missed altogether. In essence therefore, ultrasonography cannot be used effectively by an operator who is not experienced in transrectal palpation.
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In the image above, the operator is holding the transducer against the cranio-dorsal surface of the cranial margin of the left uterine horn. This may provide a good image but it best to place the transducer against the cranial surface of the horn, pulling back slightly so as to exclude any viscera or abdominal gas from the space between the transducer and the uterus. Conversely, when one uses pressure on the dorsal surface alone, the uterus easily moves away easily, opening gaps between the uterus and transducer.
In the image below the transducer has been moved to the location of the ovary, previously determined by transrectal palpation.
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Practicing equine stud medicine without ultrasonography is akin to practicing cardiology without a stethoscope.
The contralateral uterine horn is examined. .
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Because sector transducers are not used for transrectal examinations, virtually all images are obtained as cross sections in saggital orientation. Therefore the view below would be typical of a uterine horn during routine examination. The lumen of the uterus is never obvious unless it contains fluid or gas. The non-echogenic object in the center of the uterine cross section is a 12 day old embryo.
As shown below, it is important to examine the tract carefully as the transducer is withdrawn. It is rocked from side to side so the lumen of the body is thoroughly examined. It is common to miss an embryo in the body of the uterus if this is not done. This error will become all too obvious when the mare aborts twins late in gestation. See this LORI entry in that regard.
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Blood on a rectal sleeve is never a welcome sight. It is common in cattle but in mares, a cause for alarm. Fortunately it does not always indicate that the rectum has been seriously torn. These mares should be examined carefully by a highly experienced operator when this occurs. If there is an obvious tear, the mare should be sent to a referral institution immediately. This should be done even if the tear is not full-thickness because small tears can enlarge over several days, eventually penetrating into the peritoneal cavity.
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If the tear is not palpable, the mare should be examined at 24 hour intervals to ensure that the tear continues to be non-palpable. It is advisable to recommended that the mare's body temperature be monitored closely as well. Should the temperature rise, broad spectrum antibiotic treatment should be started and the mare should be referred for surgical inspection.
In some cases where veterinarians have torn the rectum and law suits have been successful, it was demonstrated by legal council for the plaintiff, that diligent and caring follow-up by the veterinarian was absent. It is generally acknowledged that fatal rectal tears can occur during transrectal examination; a daily hazard faced by those in stud practice. If such an accident should occur, it is incumbent upon the veterinarian to follow up on all suspected tears with the greatest diligence possible.
