TL;DR: Sudden hind leg paralysis and vocalization in cats is a life-threatening emergency typically caused by a blood clot; seek immediate 24-hour emergency veterinary care to address extreme pain and stabilize your pet.
What causes sudden hind leg paralysis and pain in my cat?
When a cat suddenly loses the use of their back legs and begins vocalizing loudly, it is frequently caused by a Feline Aortic Thromboembolism (FATE), also known as a saddle thrombus. This occurs when a blood clot, often originating from the heart, travels through the aorta and becomes lodged at the junction where the blood supply splits to the hind limbs. This cuts off blood flow, leading to sudden paralysis, cold limbs, and intense pain.
How urgent is it if my cat loses the use of their back legs?
- This situation is a life-threatening medical emergency.
- The level of pain associated with a saddle thrombus is extreme, and without immediate intervention, the prognosis is very poor.
- You should not wait for an appointment or monitor the situation at home.
- Please transport your cat to the nearest 24-hour emergency veterinary hospital immediately.
How can a photo or video help the emergency veterinarian treat my cat?
- If you can safely do so without delaying your departure, take a quick video of your cat's movement.
- Take a clear photo of their back paw pads, as they often appear pale or blue due to the lack of oxygenated blood.
- Share these visuals with the triage nurse upon arrival to help them prioritize your cat's care and begin pain management even faster.
Clinical Context (Merck Veterinary Manual)
In cats presenting with dragging of the back legs and vocalization, a primary differential is arterial thromboembolism, often associated with underlying cardiomyopathy. Clinical signs include posterior paresis or paralysis, extreme pain, firm gastrocnemius muscles, and potentially urinary and fecal incontinence. Diagnosis is based on clinical signs, physical examination findings, and Doppler blood flow readings of the hindlimbs; ultrasound can also be used to identify the thromboembolus. Pathologic changes include focal muscle necrosis and degeneration of the sciatic nerve. Management consists of analgesics, nursing care, and treatment of any underlying disease. Anticoagulants, such as unfractionated heparin or low-molecular-weight heparin, are used to reduce continued thrombus formation. Neurologic deficits may improve within 2-3 weeks, but complete recovery may take up to 6 months; permanent deficits are possible. The prognosis is guarded, with a high rate of mortality or euthanasia during the initial episode.
Chapter: Cardiology
Source: The Merck Veterinary Manual, 11th Edition (Page 1245)