⚠️ Vet’s 2025 Guide to Aneurysms in Horses

By Dr Duncan Houston BVSc

1. 🩺 What Is an Aneurysm?

An aneurysm is an abnormal bulging of a blood vessel due to weakening of the vessel wall. In horses, this most often involves arteries—especially the aorta, critical vessels in the abdomen, or less commonly, veins like the jugular. These vessel dilations risk rupture and internal bleeding, often with grave outcomes :contentReference[oaicite:3]{index=3}.

2. Types of Aneurysms in Horses

• Aortic aneurysms: Common at the aortic root or arch—rupture is often rapidly fatal :contentReference[oaicite:4]{index=4}.
• Abdominal/iliac aneurysms: May run alongside thrombosis in the terminal aorta—hindlimb weakness is a key sign :contentReference[oaicite:5]{index=5}.
• Intestinal aneurysms: Often associated with artery damage by Strongylus vulgaris larvae :contentReference[oaicite:6]{index=6}.
• Venous aneurysms: Congenital jugular dilations; usually benign :contentReference[oaicite:7]{index=7}.

3. Causes & Risk Factors

• Congenital defects: Especially aortic root dilations seen in stallions :contentReference[oaicite:8]{index=8}.
• Parasitic damage: Strongylus vulgaris can infect vessel walls, promoting aneurysm and thrombosis :contentReference[oaicite:9]{index=9}.
• Infection-related (mycotic): Aspiring fungus or bacteria can cause destructive arterial disease :contentReference[oaicite:10]{index=10}.
• Physical trauma or inflammation: Often idiopathic or secondary to other vascular disease :contentReference[oaicite:11]{index=11}.

4. Clinical Signs: Recognising the Threat

Signs depend on aneurysm location and rupture status:

• Sudden death: Classic for ruptured aortic aneurysms—occurs within minutes :contentReference[oaicite:12]{index=12}.
• Signs before rupture: Tachycardia, tachypnea, colic signs, peripheral edema, exercise intolerance—especially in Friesians with chronic aortic damage :contentReference[oaicite:13]{index=13}.
• Hindlimb issues: Weakness, lameness, cold limbs, reduced pulses suggest abdominal/iliac involvement :contentReference[oaicite:14]{index=14}.
• Digestive or urinary signs: Rare internal aneurysms may cause colic or hematuria :contentReference[oaicite:15]{index=15}.

5. How Veterinarians Diagnose Aneurysms

• Physical exam: Listen for murmurs, assess mucous membranes, pulse quality, rectal palpation for iliac pulse variations :contentReference[oaicite:16]{index=16}.
• Bloodwork: Non-specific—look for anemia or inflammation.
• Ultrasound/Echocardiography: Essential for visualising aortic root aneurysms or abdominal vessel involvement :contentReference[oaicite:17]{index=17}.
• Advanced imaging: CT or MRI useful for internal or thoracic cases :contentReference[oaicite:18]{index=18}.
• Post-mortem exam: Confirms rupture sites, arteriovenous fistulations :contentReference[oaicite:19]{index=19}.

6. Treatment & Emergency Response

6.1 Emergency Care (If Unruptured or Acute)

• Stabilise: IV fluids, oxygen, anti-inflammatories, analgesia attempt to maintain perfusion.
• Manage blood pressure and clotting: Diuretics or anticoagulants may be considered in consultation with a specialist :contentReference[oaicite:20]{index=20}.
• Develop a long-term management plan if aneurysm remains intact—though options are limited.

6.2 Post-Rupture Response

Rupture usually fatal—intensive support rarely succeeds. Euthanasia may be considered humane in cases of catastrophic bleed :contentReference[oaicite:21]{index=21}.

6.3 Thrombosis and Iliac Occlusion

• Mild cases may respond to rest and vasodilators; severe cases with paralysis often have poor prognosis :contentReference[oaicite:22]{index=22}.
• Supportive laminologists, anti-inflammatories, and passive limb warming may assist circulation.

7. Prognosis: A Delicate Balance

• Ruptured aneurysm: very poor.
• Detectable, stable aneurysm: guarded—monitor closely.
• Iliac thrombosis: poor if hindlimb paralysis; mild signs may improve with therapy.
• Breed predisposition: Friesians are overrepresented :contentReference[oaicite:23]{index=23}.

8. Prevention Strategies

• Regular deworming protocols to prevent arterial damage from parasites :contentReference[oaicite:24]{index=24}.
• Cardiovascular screenings for at-risk horses—older stallions, Friesians, breeding stock.
• Prompt treatment of infections that may seed arteritis.
• Avoid high-intensity exercise in horses with known aneurysms.

9. Case Examples

Friesian gelding with chronic signs: Repeated colic episodes, limb swelling, tachycardia. Ultrasound confirmed aortic arch aneurysm. Managed conservatively, euthanised on sudden collapse :contentReference[oaicite:25]{index=25}.

Foal with abdominal aneurysm: Three-month-old foal showed hematuria and colic. Imaging revealed infected umbilical artery aneurysm at aortic bifurcation—euthanased due to poor prognosis :contentReference[oaicite:26]{index=26}.

10. Ask A Vet Support 🩺

At Ask A Vet, we help owners recognise subtle signs—schedule cardiac screenings, assist with ultrasound triage, interpret lab results, manage thrombosis, and support decisions in urgent scenarios. Download our app for 24/7 access to equine cardiovascular specialists.

11. Quick Reference Table

12. Final Thoughts

Aneurysms in horses are rare but can be devastating. Recognising clinical patterns—colic, hindlimb weakness, tachycardia—and acting quickly with diagnostics and support can sometimes save lives. Preventive strategies and early detection via cardiovascular screening are crucial in high-risk horses. Trust Ask A Vet for timely advice, diagnostics coordination, and compassionate guidance when these silent threats emerge. ❤️

Download the Ask A Vet app today to partner with equine cardiovascular experts and safeguard your horse’s vascular health in 2025 and beyond.