Cat with sudden hindleg paralysis (saddle thrombus)
Sudden hindleg weakness and crying out in a cat is almost always saddle thrombus — phone the emergency vet now; this is one of the most painful feline emergencies.
Recognise the signs
- Sudden inability to use one or both back legs
- Loud vocalisation, crying, screaming from pain
- Hindlegs cold to the touch
- Pads of affected legs pale, blue, or purple
- Pulse absent in the back legs (front leg pulses normal)
- Fast breathing, open-mouth breathing, distress
- Often the first indication that the cat had heart disease at all
First aid steps
- Phone the emergency vet immediately and describe the signs.
- Place the cat gently in a carrier with soft padding — handling is painful, move with care.
- Do not attempt to massage or warm the legs aggressively.
- Drive without delay.
- Note the time signs first appeared — often very precise (cat was fine 10 minutes ago).
Do NOT
- Do not give any human painkillers — paracetamol kills cats, NSAIDs are unsafe.
- Do not try to walk the cat or massage circulation back.
- Do not delay to 'see if it improves' — outcomes are best with early specialist treatment.
- Do not handle a screaming cat with bare hands beyond what is needed for the carrier — pain bites are common.
While transporting to the vet
- Keep the carrier flat and stable.
- Cover with a light blanket for warmth and to reduce stress.
- Phone ahead — pain relief, oxygen, and cardiac assessment will be prepared.
When to phone the vet immediately
- Any sudden hindleg weakness or paralysis in a cat is an emergency
- Open-mouth breathing — heart failure may be developing alongside the clot
- Severe pain and distress
- Cold, blue paws
Common causes
- Underlying hypertrophic cardiomyopathy (HCM) — often previously undiagnosed
- Other cardiomyopathies and heart disease
- Hyperthyroidism with secondary heart changes
- Any condition causing blood pooling in the heart and clot formation
What the vet will need to know
- Exact time signs started
- Whether one or both back legs affected
- Any previous heart murmur, breathing changes, or hyperthyroidism
- Current medications
- Recent stress events (boarding, travel, vet visit)
Aftercare
- Treatment focuses on pain relief, oxygen, and managing underlying heart disease — clot-busting drugs are rarely used due to risk.
- Prognosis is guarded — many cats euthanised on welfare grounds; some recover partial leg function over days to weeks.
- Survivors need lifelong heart medication and clot-prevention drugs (clopidogrel).
- Recurrence is common — owners should have a clear plan with the vet.
Prevention
- Annual checks with auscultation — many heart conditions are silent until a clot or heart failure occurs.
- Investigate any heart murmur with echocardiography, especially in at-risk breeds.
- Treat hyperthyroidism promptly when diagnosed.
- Once a cat has any cardiomyopathy, clopidogrel is often prescribed to reduce clot risk.
Breed-specific notes
- Higher cardiomyopathy incidence: Maine Coon, Ragdoll, British Shorthair, Sphynx, Persian.
- Any cat over middle-age can develop HCM regardless of breed.
Frequently asked questions
Why is saddle thrombus so painful?
The clot blocks blood flow to the back legs, causing sudden tissue ischaemia — comparable to a severe limb infarct in a person. The vocalisation and distress are among the most striking signs in feline emergency medicine.
Can my cat recover from saddle thrombus?
Some cats recover partial or full leg use over days to weeks with intensive supportive care, but the underlying heart disease persists and recurrence rates are high. Many owners and vets choose euthanasia on welfare grounds; this is a difficult, individual decision based on severity, response to treatment, and quality of life.
How can I check for heart disease before a clot happens?
Annual vet checks with stethoscope examination catch many murmurs, but some cardiomyopathies are silent. For at-risk breeds, screening echocardiography by a cardiologist is the gold standard — often offered at breed club health schemes.