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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Involution is normally complete by 13–25 days, with the exception of normal size, which may require as long as 35 days.
  • Delayed uterine involution may be the result of size, tone, endometrial regeneration, or elimination of bacteria from the uterine lumen

Pathophysiology!!navigator!!

  • Placentation in the equine is diffuse allantochorial microcotyledonary, which allows rapid uterine involution.
  • Microcaruncular involution is complete by day 9 postpartum and complete histologic repair is observed by day 14.
  • DUC may follow dystocia or RFM and is characterized by compromised ability to eliminate postpartum debris and bacteria from the uterus.
  • DUC origin can be:
    • Mechanical, e.g. decreased muscular contractions, decreased exercise.
    • Inflammatory, e.g. neutrophil influx.
    • Immunologic

Systems Affected!!navigator!!

Reproductive

Signalment!!navigator!!

  • Any mare.
  • More prevalent in old mares.
  • Draft breeds are predisposed

Signs!!navigator!!

General Comments

Rapid uterine involution is necessary in mares because foal heat and rebreeding can occur within 5–18 days postpartum.

Historical Findings

Suspected if failure to conceive when bred during an early foal heat.

Physical Examination Findings

Increased uterine size, intrauterine fluid, or abnormal vaginal discharge.

Causes!!navigator!!

  • Anatomic defects.
  • Poor uterine contraction.
  • Poor uterine clearance

Risk Factors!!navigator!!

  • Old mares.
  • Dystocia and RFM.
  • Contaminated uterus at parturition

Diagnosis ⬆ ⬇

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DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Metritis.
  • Delayed uterine involution may accompany metritis

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

Endometrial cytology—presence of neutrophils.

Imaging!!navigator!!

US

  • Fluid within the postpartum uterine lumen.
  • Decreased uterine tone and/or increased uterine size

Other Diagnostic Procedures!!navigator!!

Endometrial bacteriology.

Pathologic Findings!!navigator!!

Indicators of delayed uterine involution, 12–15 days postpartum.

Uterus

  • Intraluminal fluid.
  • Decreased tone.
  • Endometrial cytology, increased number of leukocytes

Vulva/Vulvar

Discharge persists.

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • May accompany uterine infections or inflammation.
  • Systemic antibiotics are not indicated.
  • Local, intrauterine instillation of antibiotics may be contraindicated

Activity!!navigator!!

Normal activity.

Client Education!!navigator!!

  • Not all mares are ready to be bred at foal heat.
  • All mares should undergo a postpartum examination even if foaling appeared to be normal.
  • Decision for foal heat breeding should be based on serial TRP

Medications ⬆ ⬇

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MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Oxytocin (10 IU IV or 20 IU IM every 2 h for the first 24 h postpartum) and prostaglandin F2α (10 mg IM) or a prostaglandin analog (cloprostenol 250 µg IM) have been used to promote uterine involution, but their efficacy is not known.
  • Uterine flushes when indicated (i.e. presence of a large amount of intrauterine debris).
  • Antibiotics—only if a bacterial pathogen is confirmed present

Precautions!!navigator!!

Do not overtreat delayed uterine involution with unnecessary antibiotics or other local or systemic medications.

Follow-up ⬆ ⬇

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FOLLOW-UP

Patient Monitoring!!navigator!!

Examination of the uterus to determine return to normal is essential after therapy—TRP; ultrasonography.

Prevention/Avoidance!!navigator!!

  • Light exercise during late gestation and postpartum.
  • Barn hygiene—mare's stall should be bedded with clean straw for foaling and during the first several days postpartum

Possible Complications!!navigator!!

  • Failure to conceive.
  • Early embryonic death

Expected Course and Prognosis!!navigator!!

  • Majority of mares return to normal without treatment.
  • In some cases, involution remains incomplete and may prevent conception or pregnancy maintenance

Miscellaneous ⬆ ⬇

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MISCELLANEOUS

Associated Conditions!!navigator!!

May or may not be coupled with a uterine infection.

Abbreviations!!navigator!!

  • DUC = delayed uterine clearance.
  • RFM = retained fetal membranes.
  • TRP = transrectal palpation

Suggested Reading ⬆ ⬇

Carluccio A, Contri A, Tosi U, et al. Survival rate and short-term fertility rate associated with the use of fetotomy for resolution of dystocia in mares: 72 cases (1991-2005). J Am Vet Med Assoc 2007;230:1502–1505.

McKinnon AO, Squires EL, Harrison LA, et al. Ultrasonographic studies on the reproductive tract of mares after parturition: effect of involution and uterine fluid on pregnancy rates in mares with normal and delayed first postpartum ovulatory cycles. J Am Vet Med Assoc 1988;192:350–353.

Steiger K, Kersten F, Aupperle H, et al. Puerperal involution in the mare—morphological studies in correlation with course of birth. Theriogenology2002;58:783–786.

Stewart DR, Kindahl H, Stabenfeldt GH, Hughes JP. Concentrations of 15-keto-13,14-dihydroprostaglandin PGF2α in the mare during spontaneous and oxytocin induced foaling. Equine Vet J 1984;16:270–274.

Author(s) ⬆

Author: Ahmed Tibary

Consulting Editor: Carla L. Carleton

Acknowledgment: The author and editor acknowledge the prior contribution of Walter R. Threlfall.