Therio Exam 1: Equine Rectal Tears/Twins, Parturition/Induction/Dystocia, Pregnancy Loss

Rectal tears

What is an inherent risk of rectal palpation?

Arabians, ponies

What horse breeds are predisposed to rectal tears?

*Young fractious animals & older mares (Deep pendulous tracts/ age related degeneration in GI tract) are also at risk

Grade 1

Rectal tear grade with disruption of only the mucosa & submucosa

*May be difficult to feel

Grade 2

Rectal tear grade with Mucosa & submucosa intact, only the muscular layer disrupted

-Rare grade; No blood on sleeve & no treatment without creating a stricture

Grade 3

Rectal tear grade with mucosa, submucosa, & muscular layers are disrupted

-Only the serosal layer is intact

*Will develop peritonitis even though there isn't communication with peritoneal cavity (due to bacterial translocation through thin serosal layer)

Grade 4

Rectal tear grade with all layers are disrupted

-Rectum directly communicates with the peritoneal cavity (abdomen)

*Grave (fatal) prognosis

Rectal tears

What do these methods minimize in horses:

-Educate novice clients about inherent risks

-Provide adequate restraint appropriate for the mare

-Adequate lubrication

-Relax with peristaltic waves

-Insert hand past the structure being palpated

-Completely evacuate the rectum (unlike palpating cows)

-Turn sleeve inside out so the seam doesn't cause irritation

Rectal tears

What condition is suspected when blood is observed on the rectal sleeve (amount/color are valuable indicators of severity)?

First aid treatment

What type of treatment is this for Rectal Tears:

-Antibiotics; Potassium penicillin and gentamicin

-Flunixin meglumine (banamine)

-Tetanus toxoid vaccine

-Evacuate the rectum of fecal balls

-Mineral oil or Magnalax®

-Call referral clinic

-Rectal packing

-+/- Epidural

Grade 1

What grade rectal tear has the following treatments:

-First Aid

-Broad spectrum antibiotics

-NSAIDS

-Stool Softeners

-Manual evacuation

-Fast the horse for 24 hrs

No, could create a stricture

Do you treat grade 2 rectal tears? Why or why not?

Grade 3

What grade rectal tear has the following treatments:

-Rectal Liner

-Loop colostomy

-Blind suture via rectum

-Medical management is the same as for Grade 1

-Manual evacuation of rectum every 2-3 hours since tear is deeper

-Gently pack the defect with Betadine soaked gauze/cotton

-+/- Peritoneal lavage

Grade 4

What grade rectal tear has the following treatments:

-Rectal Liner: defecate through this ring/sleeve to bypass the rectal tear (compresses rectum like a banded calf)

-Loop colostomy: attaches small colon to rectum to create a stoma (defecates out of flank while rectum repairs)

-Blind suture via rectum

-Rectal packing

Inappropriate aftercare

Most common cause of malpractice claims with rectal tears

*Negligence in communication (not telling the owners there is a tear), treatment or both

Late term abortion

Twinning is undesirable condition in mares because it almost always results in a ...

*Which can lead to Dystocia, Retained placenta, Delayed uterine involution, Metritis, Death of both twins, +/- mare

Before day 16

When is the ideal time to manage twins in mares?

Opposite horns

Does fixing in the opposite horns (bilateral fixation) or in the same horn (unilateral fixation) make natural reduction of twins unlikely?

Thoroughbreds

What horse breed has the highest incidence of double ovulations?

Dizygotic (fraternal)

Most twin pregnancies in horses are _____, resulting from multiple ovulations during a single estrous cycle where 2 separate eggs are released & fertilized.

Bilateral ovulation

Occurs when 2 dominant follicles release an oocyte from both the left & right ovaries during the same estrous cycle

Bilateral ovulation

Is unilateral or bilateral ovulation more likely to produce a twin?

False (Used to be the #1 cause but thanks to earlier screening with US, placentitis is now the #1 cause of pregnancy loss)

True or False: Twins are the #1 cause of pregnancy loss in mares.

Day 13-15

For Pregnancy checks, try to ultrasound mare on day ___-___ post-ovulation.

*If 2 vesicles are found, twins are diagnosed --> manually crush 1 of the twins & then recheck mare in 2-3 days

ECG (equine chorionic gonadotropin)

If the mare is not checked until 35-40 days post-ovulation, ____ is now being produced by endometrial cups.

-If pregnancy is terminated at this point, the mare won't cycle predictable that year so the season is lost

Twin reduction methods

What do the following methods do:

- Manual crushing

- Transvaginal, ultrasound-guided twin reduction

- Cranio-cervical dislocation at Day 65-85

- Transcutaneous, ultrasound-guided twin reduction

- Elective termination of both pregnancies

True

True or False: The best time to manage twin pregnancies in mares is during the mobility phase before day 16.

Anovulatory follicles, Hematoma, Gonadostromal (sex cord) tumors

What are the 3 most Common Ovarian Abnormalities (from most to least common)?

Gonadostromal (sex cord) tumors

Which of these common ovarian abnormalities is due to neoplasia, not an acquired condition?

-Anovulatory follicles

-Hematoma

-Gonadostromal (sex cord) tumors

Anovulatory follicle

Preovulatory follicle that fails to ovulate

-Appear normal until just prior to ovulation (usually "too late")

-Incidence: 5% in early season, 20% in late season

Hypoechoic, cobweb

The contents of Anovulatory follicles may range from uniformly ____ to ____ appearance.

Progesterone, PGF2A

The majority of Anovulatory Follicles luteinize & produce _____. Since this follicle is PG responsive, an injection of ____ on Day 6 of diestrus can be given to return the mare to estrus.

Germinal inclusion Cysts

Ovarian cyst that forms when the peritoneum becomes embedded in the ovulation fossa

*Mare excessively hemorrhages into follicular lumen

50 mm+

What is the size threshold for differentiating germinal inclusion cysts from regular follicles?

*No follicle regardless of breed should be this large

Germinal inclusion Cysts

Nonpathologic cysts that can cause effacement of the ovary

-Hemorrhage often occurs immediately following ovulation

Granulosa theca cell tumor

Sex cord (gonadostromal) tumor that's the MOST common reproductive tumor in horses

*#1 neoplastic ovarian abnormality

Granulosa theca cell tumor (1st), Teratoma (2nd), Dysgerminoma (3rd), Cystadenoma (3rd)

List the 4 Neoplastic Ovarian abnormalities from most to least common

Granulosa theca cell tumor

Ovarian tumor that is hormonally active

*Present with anestrus or inconsistent cycling

-Usually not cycling at time of discovery → hard to catch them early

Inhibin

What hormone will be elevated 90% of the time with Granulosa theca cell tumors?

-Causes anestrus due to downregulation of FSH

Testosterone

What hormone is elevated 50-60% of the time with Granulosa theca cell tumors & will cause the mare to act stallion like?

Prolonged anestrus

What behavior is most commonly seen in mares with Granulosa theca cell tumors?

*Can also see Continuous or intermittent estrus (nymphomania) or Stallion-like behavior

Teratoma

Benign germ cell tumor composed of totipotent cells that will grow overtime

*Usually an accidental finding in non-breeding animals

Hard, hyperechoic (echodense)

A Teratoma will feel ____ on palpation & ____ on ultrasound.

*Surgical removal recommended due to potential growth

Dysgerminoma

Rare, Malignant ovarian tumor of germ cell origin (Primordial germ cells)

*Similarity to testicular tumor

-Can cause Systemic illness & Weight loss with a poor prognosis due to remote metastasis

Cystadenoma

Benign epithelial ovarian tumor arising from surface epithelium

-Rarely steroidogenically active

-May lead to complete effacement of ovary

Mesonephric duct, Paramesonephric duct

What embryonic structures are likely involved in Images A & B?

Granulosa theca cell tumor

Which of these ovarian abnormalities affects the contralateral ovary:

-Anovulatory follicles

-Ovarian Hematoma

-Granulosa theca cell tumors

-Teratoma

-Cystadenoma

Anovulatory follicle

A mare is in heat for 4 days and a 40 mm follicle was found on the R. ovary. About 3 days later this follicle is the same size. What ovarian abnormality is likely present?

Pre-ovulatory follicle, anovulatory follicle

Identify the follicles:

-A = Large, uniform hypoechoic (black) area

-B = "Snow storm" appearance mixed with black & white contents in follicle with sometimes a hyperechoic (white) edge due to luteal tissue

Anovulatory follicle, Hematoma

Identify these ovarian abnormalities on US

*Notice the difference in size

Granulosa theca cell tumor

What ovarian abnormality has this honeycomb appearance on US?

Downregulation of FSH by inhibin and GnRH by Testosterone

Describe why a granulosa theca cell tumor inactivates the contralateral ovary?

Walnut sized

How would you describe the contralateral ovary if a granulosa theca cell tumor was present?

Cystadenoma

If there is an ovarian tumor & the contralateral ovary has a 35 mm follicle, is the tumor likely a granuloma theca cell tumor or a cystadenoma?

Ultrasound

What diagnostic method can be used to find these ovarian abnormalities:

-Anovulatory follicles

-Ovarian hematoma

-Granulosa Theca Cell

-Dysgerminoma

-Cystadenoma

Histopathology (following tumor removal)

Definitive diagnosis for a Granulosa Theca Cell Tumor

Hormone levels

The lab at UC-Davis has a Granulosa Theca Cell Tumor panel to test ...

Inhibin, Anti-Mullerian hormone, testosterone

What 3 hormones will be elevated the majority of the time with a Granulosa Theca Cell Tumor?

Progesterone (because they're not cycling = no ovulation = no CL creation = no P4 production)

What hormone will be low in almost every case with a Granulosa Theca Cell Tumor?

Granulosa theca cell tumor, teratomas

What 2 ovarian tumors can be surgically removed via:

-Colpotomy

-Flank laparotomy

-Ventral midline laparotomy

True

True or False: With Granulosa theca cell tumors, the

contralateral ovary should resume cyclicity generally within a year (next breeding season).

False (good prognosis for mare & ferility)

True or False: The prognosis for mares with granulosa theca cell tumors is poor.

Optimize concentrations of colostral immunoglobulins

What is the benefit of boostering vaccines 4-6 weeks prior to expected foaling in the dam?

Killed

Are the pre-foaling vaccines a killed or live vaccine?

-Vaccine: Pneumabort K + 1b to protect against EHV-1 abortions

5, 7, 9 months

At what points of gestation should the Pneumabort K + 1b - killed vaccine be administered?

*To Protect against EHV-1 abortions

340 days, < 320 days

What is the average gestation length in mares? Premature?

Winter/early spring

Will mares that foal in the late summer/fall or winter/early spring foal 5-10 days later?

10 days

How much does artificial lighting reduce gestation length by?

Male

Are male or female foals carried longer?

Fescue

Ingested toxins (ergot alkaloids) in what type of grass can prolong gestation?

*Environmental stressor

Fetus

Does the mare or fetus trigger parturition?

Night (93% gave birth between 9 pm and 8 am)

Do the majority of mares foal during the day or at night?

Delayed

Can excessive human activity cause premature or delayed foaling?

Mammary gland development

First noticeable change in mares that occurs 2-6 weeks prior to foaling

*More pronounced or develops earlier in multiparous mares

Waxing of teat ends

Most commonly observed clinical sign in mares that occurs 48-72 hours prior to foaling

-Thick, waxy exudate

70% (And 70% of these waxy mares will foal within 24-48 hours)

What % of mares will have waxy teat ends prior to parturition?

Dripping milk

Parturition sign that occurs minutes to 24 hours prior to foaling due to an Oxytocin release

-Can indicate stage 1 of labor

-Not reliable in mares that have had multiple foals & can occur if a mare sees a foal

Elongation and swelling of the vulva

What clinical sign of parturition occurs 0-24 hours prior to foaling?

*Don't confuse with Perineal relaxation (softening of vulva & other caudal tissues that occurs 1-3 wks prior)

7-10 days

How many days prior to foaling does the colostrum come in?

Electrolytes, pH

What 2 tests can be conducted on the milk to predict when parturition will occur

Sodium/Potassium ratio (Inverse 4 days prior to foaling), calcium levels (> 200 pm = likely to foal in 48-72 hrs)

What 2 values are evaluated on a Milk electrolyte test?

FoalWatch

Quantitative chemical reaction measuring calcium carbonate to predict parturition

-Color change when Ca > 200pm: Orange-pink to blue

Predict-A-Foal

Test strip that measures Calcium & Magnesium to predict parturition

-Color change when Ca > 200pm: green to red

Decreases (Drops to 6.4)

Does the Milk pH increase or decrease prior to foaling?

-Normal pH in late gestation: 7.0-7.4

*Less sensitive & less accurate than Ca

Foalert

Transmitter sutured to the vulva that autodials staff when the foal engages the cervix & its foot passes through the vulva

*Problem: By the time they alert you, you won't get there in time

Preparation, Foal delivery, Fetal membrane passage

What are the 3 stages of labor?

1-4 hours

How long does Stage 1 of parturition last?

Stage 1

Parturition stage where the mare is restless, nervous, lying up/down frequently, & pawing

-Dripping milk

-Look at flanks/abdominal discomfort

*Shorter & less obvious in multiparous mares

Uterine contractions, chorioallantois

Stage 1 Part. Markers:

-Start: onset of ____ ____

-End: rupture of ____

5-20 minutes

How long does Stage 2 of parturition last?

Chorioallantois, foal

Stage 2 Part. Markers:

-Start: rupture of ____

-End: Delivery of ____

Stage 2

Parturition stage where there is active straining, appearance of amnion @ vulva, & Ferguson's reflex

Ferguson's reflex

Oxytocin release triggered when the foal's head & front feet stretch the cervix during stage 2 labor

*Causes uterine contractions

Eponychium (foal slippers)

Soft, rubbery tissue layer that covers a newborn foal's hooves at birth to protect the birth canal during parturition

Head 1st with forelimbs & head extended (nose @ carpus, soles of feet facing down, foal facing dorsosacral to mare)

What is the normal (ideal) position of the foal during parturition?

20 minutes

How much time has to pass in Stage 2 of parturition without progress/delivery before assistance is needed?

45-90 minutes

How long is stage 3 of parturition?

*Passing of fetal membranes (placenta)

3 hours

How much time must pass after delivering the foal without passing the placenta to diagnose a retained placenta?

Tie placenta in knot, Oxytocin inj

What are the 2 main ways to handle a retained placenta?

*Burn's technique is the next step if these fail (Passes NG tube into uterus & distends it with water to peel away the placental attachments)

True

True or False: Elective induction of pregnant mares is not recommended.

Labor induction

What are these conditions indications for in a pregnant mare:

-High risk pregnancies

-Hx of Dystocia, stillbirth, premature placental separation (red-bag)

-Neonatal isoerythrolysis

-Severe acute laminitis

-Ruptured prepubic tendon

-Hydrops