section name header

Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • A result of RFM or contamination of the uterus by bacteria after parturition or dystocia
  • Marked by inflammation of the deep layers of the uterus, endotoxemia and/or septicemia, and laminitis

Pathophysiology!!navigator!!

  • After foaling, RFM, or kept stall bound, trauma and bacterial contamination of the uterus causes an inflammatory response, with nitric oxide production that decreases uterine contractility so debris, bacteria, endotoxins, and inflammatory byproducts are not expelled
  • Accumulation of fluid, bacterial growth, inflammation, and toxin absorption may lead to septicemia, endotoxemia, and laminitis

Systems Affected!!navigator!!

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

N/A

Signalment!!navigator!!

  • Most common after a dystocia, associated with RFM, or extensive intrapartum uterine contamination
  • Can occur after a normal delivery if uterine contraction and involution does not occur

Signs!!navigator!!

  • Metritis may be evident by 12–24 h postpartum, characterized by depression, abdominal discomfort, and anorexia
  • Pyrexia, elevated pulse and respiratory rate, congested or toxic mucous membranes with shock, endotoxemia, or septicemia
  • Uterus is enlarged, flaccid, and pendulous from accumulation of fetid, thick tan to chocolate-colored fluid
  • The RFM may either be composed of a large portion of the total placenta with a free portion seen hanging through the vulva or be limited to only a small piece of the remaining placenta usually in the nongravid horn
  • Signs of laminitis may appear 12 h to 5 days postpartum

Causes!!navigator!!

  • A history of placentitis, RFM, dystocia, abortion, prolonged or assisted delivery, fetotomy, stall bound, or cesarean section increases risk of postpartum metritis
  • Postpartum complications depend on the amount and type of bacteria in the reproductive tract and the ability of the mare to clear her uterus
  • Aerobic Gram-negative and -positive bacteria such as Escherichia coli, Streptococcus zooepidemicus, and other β-hemolytic Streptococci, Staphylococcus sp., Pseudomonas aeruginosa, and Klebsiella pneumoniae are frequently involved
  • The Gram-positive anaerobe Bacteroides fragilis resides in the external genitalia of mares and stallions and mucosal breakdown and necrotic tissue create favorable conditions for this bacterium's overgrowth
  • Autolytic RFM with bacterial contamination and delayed uterine clearance initially results in endometritis, which progresses to the deeper layers; resulting in metritis
  • Metritis, left untreated, can have systemic consequences leading to endotoxemia, septicemia, and laminitis

Risk Factors!!navigator!!

See Causes.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Other Causes of Postpartum Abdominal Pain/Depression

  • Bruising of the uterus or GI tract with peritonitis
  • Uterine tear with peritonitis
  • Rupture of cecum or right ventral colon
  • Uterine artery rupture, with or without intra-abdominal hemorrhage

Other Causes of Postpartum Vaginal Discharge

  • Normal postpartum lochia (≤6 days postpartum)—odorless, dark red-brown vaginal discharge associated with a palpable, normally involuting uterus, uterine walls are thickening and rugae present
  • Vesiculovaginal reflux postpartum and vulvar discharge (thick yellow with urine crystals)

CBC/Biochemistry/Urinalysis!!navigator!!

  • Marked leukopenia (<2000 cells/µL) with toxic polymorphonuclear leukocytes/WBCs and left shift are seen in metritis. Response to treatment is evaluated by the return of WBCs to normal values (5000–12 000 cells/μl)
  • Fibrinogen may increase to >500 mg/dL during the acute phase, but usually returns to normal values (<400 mg/dL) 2–3 days after WBC count returns to the normal range

Other Laboratory Tests!!navigator!!

  • Aerobic and anaerobic uterine bacterial culture
  • Bacteroides fragilis—assume that it may be contributory if cultured
  • Large numbers of mixed flora are expected from the uterus of normal, early postpartum mares

Imaging!!navigator!!

US

  • Large amounts of fluid in the uterus 24–48 h postpartum
  • Degree of echogenicity relates to the amount of debris or inflammatory cells in the fluid
  • Uterine wall appears thick and edematous
  • RFM may be present

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

  • Postpartum acute inflammatory response can extend from the endometrium to the deeper layers, i.e. stratum compactum, stratum spongiosum, including the myometrium
  • In contrast, endometritis in the mare is limited to the endometrium and lumen

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

  • The primary objective is removal of the inciting cause—RFM, bacteria, and endotoxins from the uterine lumen. This can be accomplished with a large volume uterine lavage. A saline lavage (field treatment—12 L warm water with 150 g (6 oz) of salt added; can mix in a sterilized bucket). Infusion of 3–6 L at each treatment through a sterile nasogastric tube; uterine contents are then siphoned off; lavage repeated until the recovered fluid is clear. Depending on the mare's systemic compromise and amount and cellularity of the fluid this procedure may need to be performed 1–3 times a day
  • Intrauterine infusion with broad-spectrum antibiotics should be initiated depending on the culture and sensitivity results
  • Oxytocin to aid in uterine clearance and involution should be used but not at the same time as the above procedures
  • Systemic support can include IV fluids, antiendotoxic doses of flunixin meglumine, pentoxifylline and broad-spectrum antibiotics. Polymyxin B may be used to neutralize circulating endotoxins
  • Finding a thickened, corrugated uterine wall on palpation indicates a positive response to treatment and uterine involution
  • Unresponsive mares have flaccid, thin uterine walls and accumulate large amounts of fluid between treatments. Treatment is discontinued when intrauterine fluid is clear or normal lochia present
  • If a uterine tear is suspected begin with a smaller volume (1 L)
  • See chapter Laminitis. Icing the feet (ice boots) as a preventative measure

Nursing Care!!navigator!!

N/A

Activity!!navigator!!

Exercise—turnout as long as signs of laminitis are not present.

Diet!!navigator!!

N/A

Client Education!!navigator!!

N/A

Surgical Considerations!!navigator!!

N/A

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Fluids

  • Use polyionic solutions, e.g. Normosol
  • Estimate dehydration based on clinical signs (e.g. skin turgor), hematocrit, and total protein
  • Calcium gluconate (125 mL of 23% solution) and oxytocin (40 IU) may be added to every other 5 L bag of Normosol
  • Mild colic or discomfort will result from uterine contractions stimulated by treatment
  • Discontinue or slow the rate of administration if signs of severe colic occur

Systemic Antibiotics

  • Potassium penicillin for Gram-positive organisms—loading dose of 44 000 IU IV, followed by 22 000 IU IV QID
  • Combine with gentamicin for Gram-negative organisms—2.2 mg/kg IV QID or 6.6 mg/kg IV daily
  • For oral administration, use 15 mg/kg of trimethoprim–sulfa BID
  • Metronidazole, for anaerobes, should always be combined with IV or PO therapy—loading dose of 15 mg/kg PO, followed by 7.5 mg/kg PO QID or 15–25 mg/kg PO BID

Intrauterine Antibiotics

Uterotonic Drugs

  • Oxytocin—multiple protocols have been proposed and used
    • 10 IU IV or 20 IU IM after uterine lavage if no intrauterine antibiotics administered
    • 40 IU added to IV fluids
    • 10 IU IV QID

NSAIDs

  • Flunixin meglumine—antiendotoxic dose, 0.25 mg/kg IV or IM TID; anti-inflammatory dose, 1.1 mg/kg IV or IM BID
  • Phenylbutazone—4.4 mg/kg IV or PO BID; at the onset of laminitis, recommended loading dose is 8.8 mg/kg IV
  • Polymyxin B—administer 6000 U/kg IV in 1 L of sterile saline over 30–60 min; recommended BID for 1–2 days

Contraindications!!navigator!!

N/A

Precautions!!navigator!!

  • NSAIDs may cause GI ulceration and nephrotoxicity
  • Aminoglycosides can be nephrotoxic and ototoxic; ensure good hydration during treatment
  • Polymyxin B—potentially nephrotoxic at therapeutic doses
  • Dehydration and NSAID administration may potentiate the nephrotoxicity associated with aminoglycosides and polymyxin B
  • Metronidazole can decrease appetite in a number of circumstances. If it decreases appetite, then milk production in postpartum mares could be affected

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

See chapter Laminitis.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Monitor CBC for signs of endotoxemia or response to treatment
  • See chapter Laminitis
  • Monitor for signs of laminitis by early and repeated evaluation of digital pulses, signs of weight shift, and radiographs of the distal phalanx, rotation or sinking of third phalanx

Prevention/Avoidance!!navigator!!

N/A

Possible Complications!!navigator!!

  • Delayed uterine involution
  • Septicemia/endotoxemia
  • Laminitis
  • Death

Expected Course and Prognosis!!navigator!!

  • Prognosis depends on severity, duration, and secondary complications caused by metritis
  • Rapid response to therapy indicates a favorable prognosis
  • Laminitis due to postpartum metritis carries a guarded to grave prognosis

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

  • Metritis/laminitis/septicemia complex
  • Toxic metritis

Abbreviations!!navigator!!

  • GI = gastrointestinal
  • NSAID = nonsteroidal anti-inflammatory drug
  • RFM = retained fetal membranes
  • WBC = white blood cell

Suggested Reading ⬆ ⬇

Asbury AC. Care of the mare after foaling. In: MacKinnon AO, Voss JL, eds. Equine Reproduction. Philadelphia, PA: Lea & Febiger, 1993:976–980.

Canisso IF, Rodriguez JS, Sanz MG, Coutinho da Silva MA. A clinical approach to the diagnosis and treatment of retained fetal membranes with an emphasis placed on the critically ill mare. J Equine Vet Sci 2013;33:570–579.

Ricketts SW, Mackintosh ME. Role of anaerobic bacteria in equine endometritis. J Reprod Fertil Suppl 1987;35:343–351.

Threlfall WR, Carleton CL. Treatment of uterine infections in the mare. In: Morrow DA, ed. Current Therapy in Theriogenology. Philadelphia, PA: WB Saunders, 1986:730–737.

Author(s) ⬆

Author: Karen Wolfsdorf

Consulting Editor: Carla L. Carleton

Acknowledgment: The author and editor acknowledge the prior contribution of Maria E. Cadario.