Bit & Bridle

Equine Thrombophlebitis

Other Names

  • Jugular thrombophlebitis
  • Venous thrombosis
  • Catheter-associated thrombophlebitis

What is Equine Thrombophlebitis?

Equine thrombophlebitis is inflammation of a vein accompanied by the formation of a blood clot (thrombus) within the vessel. The jugular veins — which run along either side of the neck — are by far the most commonly affected vessels in horses, often as a complication of intravenous catheterisation or repeated venepuncture. When the clot becomes infected, the condition is referred to as septic thrombophlebitis, which represents a significantly more serious form of the disease.

Thrombophlebitis can vary in severity from a localised, sterile reaction that resolves with conservative management to a life-threatening condition involving extensive venous occlusion, septicaemia, or disseminated intravascular coagulation (DIC). The jugular vein is the principal site of intravenous access in horses for medication, fluid therapy, and blood collection, making this a well-recognised iatrogenic (treatment-related) complication in equine practice.

Causes

Several factors contribute to the development of thrombophlebitis in horses:

  • Intravenous catheterisation: Indwelling catheters in the jugular vein are the most common cause. Perivascular injection (injection outside the vein), movement of the catheter tip, or prolonged catheter dwell time all increase risk.
  • Repeated venepuncture: Horses requiring frequent blood sampling or intravenous medication are at higher risk, particularly if the same site is used repeatedly.
  • Irritant substances: Perivascular leakage of irritant drugs (e.g., phenylbutazone, certain antimicrobials) can cause chemical damage to vein walls.
  • Bacterial contamination: Septic thrombophlebitis most commonly involves Gram-negative bacteria such as Enterobacter spp., Klebsiella spp., or Staphylococcus spp. Poor aseptic technique during catheter placement is a significant risk factor.
  • Hypercoagulable states: Conditions such as endotoxaemia, colic, or severe systemic illness can promote a prothrombotic state that predisposes to thrombosis.

Symptoms and Signs

  • Heat, pain, and swelling along the jugular groove
  • Palpable cord-like thickening of the affected vein
  • Oedema of the head and neck (in bilateral cases or extensive unilateral occlusion)
  • Distension of facial veins
  • Pyrexia, depression, and anorexia in septic cases
  • Drainage from the catheter site or skin breakdown
  • Respiratory changes if thrombosis extends to involve thoracic vessels
  • Signs of septicaemia — tachycardia, tachypnoea, toxic mucous membranes — in severe septic cases

Diagnosis

  • Physical examination: Palpation of the jugular groove to detect swelling, heat, and cord formation. Assessment of venous filling and head/neck oedema.
  • Ultrasonography: The key diagnostic tool. Vascular ultrasound identifies the extent of thrombus formation, whether the vessel lumen is partially or completely occluded, and whether the clot is echogenic (organised) or mixed (possibly infected).
  • Haematology and biochemistry: Leucocytosis, elevated fibrinogen, and increased serum amyloid A suggest infection or systemic inflammation.
  • Culture: Blood cultures and swabs from catheter sites or any drainage to identify the causative organism in suspected septic thrombophlebitis.
  • Coagulation profile: PT, APTT, and fibrinogen levels to assess for DIC in severe cases.

Treatment

  • Remove catheter immediately: Any indwelling catheter in the affected vein should be removed promptly.
  • NSAIDs: Phenylbutazone or flunixin meglumine to reduce inflammation and pain.
  • Topical treatment: DMSO gel or furacin sweat applied along the jugular groove to reduce local inflammation; hydrotherapy with cold hosing for acute cases.
  • Antibiotics: Systemic broad-spectrum antibiotics are essential in septic thrombophlebitis. Culture results should guide choice, but empirical treatment with penicillin and gentamicin or enrofloxacin is commonly initiated pending results.
  • Anticoagulant therapy: Heparin (unfractionated or low molecular weight) may be used in severe or progressive cases to prevent thrombus extension, though evidence for its use in horses is limited.
  • Surgical intervention: Thrombectomy or venous resection may be required for extensive, non-resolving, or septic thrombi that do not respond to medical management.

For up-to-date guidance on catheter care and thrombophlebitis management, the British Equine Veterinary Association (BEVA) produces evidence-based clinical guidance.

Prevention

  • Strict aseptic technique during catheter placement and maintenance — site preparation, sterile equipment, and regular dressing changes.
  • Avoid leaving catheters in place longer than necessary; change sites if extended IV access is required.
  • Use appropriate catheter size and material; polyurethane and Teflon catheters are less thrombogenic than PVC.
  • Flush catheters regularly with heparinised saline to maintain patency.
  • Alternate venepuncture sites to avoid repeated trauma to the same location.
  • Administer irritant drugs as dilute solutions where possible and ensure correct intravenous placement before injection.

Prognosis

Sterile, mild thrombophlebitis often resolves within a few weeks with appropriate anti-inflammatory treatment, though the affected vein may remain permanently occluded. Septic thrombophlebitis carries a more guarded prognosis — mortality rates are significant if the condition progresses to septicaemia or DIC. Horses that survive severe jugular thrombophlebitis may develop collateral venous circulation and can recover to full use, though bilateral jugular occlusion carries a poor prognosis due to impaired venous return from the head.

When to Call the Vet

Contact your vet if your horse:

  • Develops swelling, heat, or pain along the jugular groove following catheterisation or venepuncture
  • Shows signs of head or neck oedema
  • Becomes pyrexic or depressed following veterinary procedures
  • Has a catheter site that shows signs of infection or discharge

Frequently Asked Questions

Can a horse survive with an occluded jugular vein?

Yes — if one jugular vein is occluded, collateral drainage via smaller vessels usually develops over time. Most horses with unilateral jugular occlusion can return to normal work. Bilateral occlusion is far more serious and can cause persistent oedema and venous hypertension of the head.

How long does jugular thrombophlebitis take to resolve?

Mild sterile cases may show significant improvement within one to two weeks with treatment, though complete resolution can take several months. Septic cases require a longer treatment course and may not fully resolve if the vein remains permanently occluded.

Is thrombophlebitis preventable?

To a large degree, yes. The majority of cases are iatrogenic (linked to medical procedures), and meticulous aseptic catheter placement and maintenance dramatically reduces the risk. However, some horses — particularly those with systemic illness — are inherently more susceptible.

Can thrombophlebitis affect veins other than the jugular?

Yes, though the jugular is by far the most common site in horses. The lateral thoracic vein and cephalic vein can also be affected following catheterisation or injection at these sites. Thrombosis of deeper vessels (e.g., portal vein) is rare but has been reported.