NAVLE Reproductive

Equine Uterine Torsion Study Guide

📅 March 28, 2026 ⏱ 25 min read

Uterine torsion is a rotation of the pregnant uterus along its longitudinal (cranio-caudal) axis, representing one of the most significant obstetric emergencies in equine practice.

Overview and Clinical Importance

Uterine torsion is a rotation of the pregnant uterus along its longitudinal (cranio-caudal) axis, representing one of the most significant obstetric emergencies in equine practice. It accounts for 5-10% of all equine obstetric emergencies and requires immediate recognition and intervention to optimize mare and foal survival. Unlike cattle, equine uterine torsion typically occurs

cranial to the cervix, making vaginal examination often unrewarding for diagnosis. The condition most commonly presents during mid to late gestation (7-11 months), with clinical signs that may be easily mistaken for gastrointestinal colic or impending parturition.

Understanding the pathophysiology, diagnostic approach, and treatment options for uterine torsion is essential for the NAVLE, as this condition tests the candidate's knowledge of equine reproductive anatomy, obstetric emergencies, and surgical decision-making.

Factor Category	Details
Fetal Activity	Vigorous fetal movement, especially in relation to maternal size; after 5 months gestation, fetal turning takes uterus with it rather than rotating freely within the lumen
Mare Activity	Sudden rolling, falls, rapid lying down or rising; getting up leading with hind legs
Gestational Timing	Most common at 7-11 months gestation; 77.5% occur before day 320 of gestation; less common at parturition
Breed Predisposition	Warmbloods and Friesians may have higher incidence; larger breeds potentially more affected
Uterine Instability	Large fetus in relatively small volume of allantoic fluid; fetal malpositioning; asymmetric uterine weight distribution

Anatomy Review: The Equine Uterus and Broad Ligaments

The equine uterus is T-shaped (bipartite), with two relatively short uterine horns (20-25 cm) joining a proportionally larger uterine body (18-20 cm). This configuration differs from ruminants and has clinical implications for torsion dynamics.

Broad Ligament Anatomy

The broad ligaments are double-layered peritoneal folds that suspend the reproductive organs from the dorsolateral body wall. They consist of three anatomically continuous portions:

Mesovarium: Attaches to the ovary; contains blood vessels supplying the ovary
Mesosalpinx: Arises from the lateral surface of the mesovarium; suspends the uterine tube
Mesometrium: The largest portion; attaches to the uterus and cranial vagina; contains uterine vessels

Protective Factors Against Torsion

The equine broad ligaments provide a relatively stable suspension system compared to cattle, which explains why uterine torsion is less common in horses. The sublumbar ovarian attachment and dorsal attachment of the broad ligaments to the body wall help maintain uterine position.

High-YieldUnlike cattle where uterine torsion often involves the cervix and vagina (post-cervical), equine uterine torsion typically occurs CRANIAL to the cervix (pre-cervical). This means vaginal examination is usually unrewarding in horses, and rectal palpation of the broad ligaments is the gold standard for diagnosis.

Parameter	Expected Finding	Clinical Significance
Heart Rate	Variable; may be elevated (greater than 48 bpm)	Heart rate at admission is a significant predictor of mare survival
Mucous Membranes	May be normal or congested/hyperemic	Indicates cardiovascular compromise if abnormal
Abdominal Auscultation	Decreased or normal borborygmi	May mimic ileus from other causes
PCV/Lactate	May be elevated in chronic cases	Indicates duration and severity of compromise

Etiology and Predisposing Factors

The exact cause of uterine torsion in mares remains uncertain, but several factors have been implicated:

Direction	Left Broad Ligament	Right Broad Ligament
Clockwise (to the right)	Stretched HORIZONTALLY over the top of the uterus, coursing cranially and to the RIGHT	Pulled VERTICALLY downward, diving UNDER the uterus (may be difficult to palpate)
Counterclockwise (to the left)	Pulled VERTICALLY downward, diving UNDER the uterus	Stretched HORIZONTALLY over the top of the uterus, coursing cranially and to the LEFT

Clinical Presentation and Signs

Clinical signs of uterine torsion are primarily those of intermittent, unresponsive colic of varying severity. The presentation can easily be confused with gastrointestinal disorders, impending parturition, or abortion.

Cardinal Clinical Signs

Intermittent colic: Mild to severe abdominal pain, often unresponsive to standard analgesics
Restlessness and sweating: Mare may appear anxious, repeatedly lying down and getting up
Straining: Frequent attempts at urination or defecation; may appear to strain as if in early labor
Flehmen response: Frequent lifting of upper lip
Anorexia: Decreased appetite often precedes other signs
Difficulty defecating: Due to pressure from twisted uterus on rectum

Physical Examination Findings

High-YieldAlways consider uterine torsion in any pregnant mare (greater than 5 months gestation) presenting with colic signs, even if signs are mild or intermittent. The classic presentation is a mare in mid-to-late gestation with intermittent, unresponsive colic that may be confused with GI disease.

Method	Indications	Advantages	Disadvantages
Rolling (Plank in Flank)	Acute torsion, less than 320 days gestation, uncomplicated, field conditions	Non-surgical, economical, can be done in field, low complication rate	Less effective at term, cannot assess uterine integrity, risk of uterine rupture
Standing Flank Laparotomy (SFL)	Uncomplicated UT less than 320 days, cooperative mare, no GI involvement	Best foal survival (88.7%), visual assessment of uterus, avoids GA risks	Requires sedation and local anesthesia, limited visibility, difficult at term
Ventral Midline Laparotomy	Greater than 320 days, suspected GI involvement, uterine compromise, cesarean needed	Complete abdominal access, can address GI lesions, visual assessment, cesarean if needed	Requires general anesthesia, higher cost, increased surgical risks
Manual Per Vaginum	At term with dilated cervix, mild torsion only	Non-invasive, immediate delivery possible	Rarely possible in horses, risk of uterine damage, limited to term

Diagnosis

Diagnosis of uterine torsion is primarily based on rectal palpation of the broad ligaments. This is the gold standard diagnostic technique and can determine both the presence and direction of torsion.

Rectal Palpation Findings

On rectal examination, the following findings are diagnostic:

Asymmetrically taut broad ligaments: One ligament is tight and pulled dorsally across the uterus, while the other dives ventrally beneath the uterus
Palpable blood vessels: The taut ligament crossing dorsally often has palpable pulsating uterine vessels
Fetus difficult to palpate: The fetus appears to be "pushed forward" into the abdomen
Tight rectum: The rectum may feel unusually tight and may twist along with the uterus

Determining Direction of Torsion

CRITICAL FOR NAVLE: Direction is described from the perspective of standing behind the mare looking cranially.

Degree of Torsion

The most common degree of torsion is 180°, but torsion can range from 180° to 540°:

Less than 180°: Broad ligaments may not be as dramatically positioned; may be subtle to diagnose
180-270°: Classic findings with clearly asymmetric broad ligament tension
Greater than 360°: Rare; severe vascular compromise likely; uterine wall may be edematous or cyanotic

Additional Diagnostic Modalities

Transrectal Ultrasonography

Used to assess fetal viability, uterine wall thickness and edema, and to visualize blood vessels in the broad ligament crossing over the uterus. Can help determine if the fetus is alive before deciding on treatment.

Transabdominal Ultrasonography

Useful for assessing fetal heart rate, fetal activity, and allantoic fluid volume. May detect uterine wall compromise (edema, thickening).

Vaginal Examination

Generally unrewarding in mares because equine uterine torsion typically occurs cranial to the cervix. If the cervix is dilated (at term), vaginal examination may reveal a spiraling of the vaginal wall, but this is uncommon. Vaginal examination is contraindicated in preterm mares to avoid cervical contamination.

NAVLE TipRemember the mnemonic for clockwise torsion: "LEFT OVER RIGHT" - the LEFT broad ligament goes OVER the uterus to the RIGHT side. For counterclockwise: "RIGHT OVER LEFT" - the RIGHT broad ligament goes OVER the uterus to the LEFT side.

Outcome	Less than 320 Days	320+ Days (Term)	Overall
Mare Survival	97% (SFL: 97.1%)	65-76%	84-90.5%
Foal Survival	72-90.6%	32-56.1%	54-82.3%
Return to Breeding	Excellent (93.5% became pregnant when rebred)	Good to excellent	93.5% pregnancy rate

Treatment Options

Treatment selection depends on the degree of torsion, gestational stage, fetal viability, uterine wall integrity, and available facilities. The goal is to detorse the uterus as quickly as possible to restore blood flow and minimize fetal and uterine compromise.

Treatment Method Comparison

Non-Surgical: Rolling Technique ("Plank in the Flank")

This is the preferred non-surgical method when available facilities allow. The goal is to hold the uterus stationary while rolling the mare's body to "catch up" with the uterine position.

Procedure

Confirm direction of torsion by rectal palpation
Induce short-term general anesthesia (xylazine + ketamine)
Place mare in lateral recumbency on the SIDE OF THE TORSION (clockwise = right side down)
Place a wooden plank (4x6 inches, 8-12 feet long) on the paralumbar fossa, cranial to tuber coxae
A person stands or sits on the plank to hold the uterus in place
Roll the mare in the DIRECTION OF THE TORSION (clockwise torsion = roll clockwise/to the right)
Confirm correction by rectal palpation; repeat if necessary

Surgical: Standing Flank Laparotomy (SFL)

The preferred surgical technique for uncomplicated uterine torsion, particularly when occurring at less than 320 days of gestation. The approach is made on the side toward which the uterus is twisted (clockwise = right flank, counterclockwise = left flank).

The surgeon reaches through the flank incision, grasps the pregnant uterus, and rocks it back and forth to build momentum before correcting the torsion. Studies show significantly better foal survival (88.7%) with SFL compared to other methods (35%).

Surgical: Ventral Midline Laparotomy

Performed under general anesthesia, this approach is indicated when:

Gestational age is greater than 320 days
Gastrointestinal involvement is suspected (up to 52.6% of cases may have concurrent GI disorders)
Uterine wall compromise (edema, necrosis, rupture) is suspected
Cesarean section is anticipated
Mare is intractable or cannot tolerate standing surgery

High-YieldStanding flank laparotomy (SFL) is the TREATMENT OF CHOICE for uncomplicated uterine torsion at less than 320 days gestation. Studies show foal survival is 88.7% with SFL versus only 35% with other methods. Mare survival is also highest with SFL at early gestational ages (97.1% vs 50% with other methods before day 320).

Complication	Clinical Significance
Uterine Rupture/Tear	May occur during correction attempts; requires surgical repair; more common with rolling technique in compromised uterus
Fetal Death	Due to compromised blood flow; more likely with prolonged torsion and torsion at term; may necessitate cesarean section or fetotomy
Abortion	May occur post-correction; often related to placental separation; 4.6% abortion rate after SFL
Periparturient Asphyxia Syndrome	Foals born to mares with torsion at term may suffer hypoxic injury due to compromised uteroplacental blood flow
Subcutaneous Seromas	Common post-surgical complication; usually self-limiting
Peritonitis	May occur with uterine rupture or contamination; requires aggressive antimicrobial therapy
Recurrence	Rare but possible; cases of clockwise followed by counterclockwise torsion in same pregnancy have been reported

Prognosis and Survival Rates

Prognosis depends significantly on gestational timing at which torsion occurs and correction method used.

Negative Prognostic Indicators

Gestational age greater than 320 days (10 months)
Elevated heart rate at admission
Prolonged duration of clinical signs (though not statistically significant in all studies)
Torsion greater than 360 degrees
Uterine wall compromise (edema, cyanosis, necrosis)
Concurrent gastrointestinal lesions
Fetal death at time of diagnosis

Complications

Complications of uterine torsion and its treatment include:

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