ISSN 2398-2977      

Uterus: rupture

pequis

Synonym(s): Uterine rupture


Introduction

  • Cause: vigorous fetal movement or fetal manipulations/fetotomy during management of dystocia. Occasionally as a result of uterine torsion, hydrops or idiopathic conditions.
  • Signs: history of foaling difficulty, prolapse of intestines into the birth canal or insidious signs of peritonitis post-foaling.
  • Diagnosis: manual palpation, transabdominal and transrectal ultrasonography and peritoneal fluid analysis.
  • Treatment: may be surgical repair of the uterus under general anesthesia or conservative therapy (if the tear is small). Systemic treatment of secondary effects.
  • Prognosis: depends on how quickly treatment is initiated, the thickness and size of the tear, the degree of contamination and the abdominal cavity and whether or not there is severe hemorrhage. If the mare survives the initial episode, the prognosis for re-breeding is generally good.
Print off the Owner factsheet on Uterine tear or rupture in the mare to give to your clients.

Pathogenesis

Etiology

  • Idiopathic.
  • "Spontaneous" uterine rupture caused by violent movement of fetal limbs within the pregnant horn at or prior to parturition.
  • Iatrogenic rupture caused by manipulation of the fetus during dystocia   Reproduction: dystocia   or fetotomy   Fetotomy  .
  • Iatrogenic perforation during replacement of a prolapsed uterus   Uterus: prolapse  .
  • Iatrogenic perforation during post-foaling uterine lavage   Uterus: lavage  .
  • Rupture due to pressure caused by amniotic or allantoic fluid accumulation in hydrops conditions   Uterus: hydroallantois / hydroamnios  .
  • Uterus torsion   Uterus: torsion  leading to rupture of devitalized uterine tissues.

Predisposing factors

General

Pathophysiology

Pre-term rupture

  • Although extremely rare, there are reports of full-thickness uterine tears occurring in late gestation, sometimes resulting in the entire fetus passing out of the uterus and into the ventral abdomen.
  • The cause of rupture may be due to violent fetal movement, stretching of the myometrium by large volumes of fetal fluids such as with hydroamnion or hydroallantois   Uterus: hydroallantois / hydroamnios  , or due to devitalization of the uterus wall following uterine torsion   Uterus: torsion  .
  • The mare may present with some degree of abdominal pain, and in hydrops conditions there will be abdominal distension.
  • Once diagnosed, the fetus is usually dead, although in some rare instances, they have survived within the abdominal cavity.

Spontaneous rupture at parturition

  • A rent in the uterine wall may be diagnosed following an apparently normal foaling.
  • Despite the protective gel-like "slippers" that cover the fetal hoovesin utero, it is thought that movement of the fetal hindlimbs can occasionally cause partial or full-thickness laceration of the uterine wall.
  • Such tears are most commonly located in the pregnant horn, especially the tip, of the uterus and are thought to occur during parturition, as the fetal stifles pass through the pelvis, allowing rapid extension of the hindlimbs.

Iatrogenic rupture

  • Intervention by an attendant or veterinarian to manipulate a fetus during dystocia can result in partial or full-thickness uterine lacerations.
  • Some malpresentations such as ventro-vertical presentation with hip flexion ("dog-sitting posture") pose a high risk of uterine damage, but lacerations can occur with almost any presentation if injudicious traction is applied to the fetus.
  • Most iatrogenic lacerations occur on the dorsal or ventral walls of the uterine body and can be caused by either the foal's hooves or by obstetrical instruments, such as fetotomy equipment.

Post-partum rupture

  • If the mare suffers endometritis   Uterus: endometritis - bacterial   following dystocia or retention of the fetal membranes, the uterine wall becomes inflamed and friable within 24-48 h of foaling.
  • Aggressive or injudicious uterine lavage   Uterus: lavage  in these cases can result in partial or full-thickness perforation of the uterine wall.

Regardless of the cause of rupture, contamination of the abdominal cavity with blood and intrauterine contents usually causes septic peritonitis. If left untreated, this will result in endotoxemia with potential sequelae, including laminitis, multiple organ dysfunction and death.

Timecourse

  • Rupture at parturition may be detected immediately if abdominal viscera are found in the birth canal or if the mare displays signs of peritonitis become apparent.
  • In mares that suffer uterine rupture secondary to uterine torsion or hydrops conditions, there may be a time interval of days to weeks between onset of the inciting cause and eventual rupture.
  • There are reports of very rare cases where mares were presented for prolonged gestation and a dead or mummified fetus has been discovered in the ventral abdominal cavity; these mares have apparently been asymptomatic and the uterus has involuted normally, suggesting that rupture may have occurred weeks or even months previously.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Rotting A K, Freeman D E, Doyle A J, Lock T & Sauberli D (2010) Total and partial ovariohysterectomy in seven mares. Equine Vet J 36 (1), 29-33 PubMed.
  • Frazer G S et al (1997) The effects of parturition and peripartum complications on the peritoneal fluid composition in mares. Theriogenology 48, 919-931 PubMed.
  • Hooper R N et al (1993) Diagnosing and treating uterine rupture in the mare. Vet Med 88 (3), 263-270 VetMedResource.
  • Fischer A T & Phillips T N (1986) Surgical repair of a ruptured uterus in five mares. Equine Vet J 18 (2), 153-155 PubMed.

Other sources of information

  • Frazer G S (2011) Dystocia Management. In: Equine Reproduction. 2nd edn. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley-Blackwell. pp 2479-2496.
  • McKinnon A O & McCue P M (2011) Uterine Abnormalities. In: Equine Reproduction. 2nd edn. Eds: McKinnon A O, Squires E L, Vaala W E & Varner D D. Wiley-Blackwell. pp 2153-2154, 2442-2443.
  • Frazer G S (2009) Postpartum Complications in the Mare. In: Current Therapy in Equine Medicine. Vol 6. Eds: Robinson N E & Sprayberry K A. pp 789-798.
  • Blanchard T L & Macpherson M L (2007) Postparturient Abnormalities. In: Current Therapy in Equine Reproduction. Eds: Samper J, Pycock J & McKinnon A. pp 465-474.
  • Story M (2007) Prefoaling and Postfoaling Complications. In: Current Therapy in Equine Reproduction. Eds: Samper J, Pycock J & McKinnon A. pp 458-464.

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