Sudden Hind Leg Paralysis in Cats: The 6-Hour Clot Window

A cat that jumped off the counter 10 minutes ago and now drags both hind legs is having a vascular emergency, not a strain. Feline aortic thromboembolism (ATE) puts a clot where the aorta splits toward the legs, and nerve and muscle damage starts in 1 to 2 hours and becomes permanent at about 6. Call the clinic before you move the cat and say hind leg paralysis and cold paw pads on the phone, so the team is ready when you walk in.

Run the 10-minute check before you drive

Watch 5 to 10 steps from 3 m away, then press 2 fingers into the groin. A limping cat still lands the paw flat, still has a femoral pulse at 140 to 220 beats per minute, and pulls the leg back when you squeeze a nail bed. A paralyzed cat does none of the three: it cannot stand after 5 minutes of trying, the pulse is missing on 1 or both sides, and a hard nail squeeze gets no response in 3 seconds. Check all 4 legs, because roughly 1 in 3 of these cats also loses a front leg, which hangs loose and stays cool while the other 3 hold 37 to 38 C.

Why the clock is 6 hours and not 24

The aorta feeds both hind legs through a narrow branch. Blocked, tissue holds on collateral flow for about 1 to 2 hours; by hour 4 the muscle leaks potassium and myoglobin; by hour 6 nerve damage no longer reverses even if flow comes back. Report the time the cat went down, not your arrival, because a team that hears hour 1 works differently from one that hears hour 7. A cat seen inside 3 hours still faces a hard outcome, but pain control, anticoagulation and, at 1 or 2 centers, clot removal stay on the table.

8 signs and the numbers behind them

Six measurements carry most of the diagnosis, each under 30 seconds.

Sign	Normal cat	Clot in the aorta	How to measure
Paw pad temperature	37 to 38 C, same on all 4	3 to 5 C cooler than the front pads	Back of 2 fingers, 5 seconds per pad
Femoral pulse	1 beat per heartbeat, 140 to 220 per minute	Absent on 1 side or both	Groin crease, 2 fingers, count 10 seconds
Nail pinch response	Leg pulls back within 1 second	Nothing after 3 seconds	Press 1 nail bed, once, firmly
Resting breathing	16 to 30 per minute	40 or more, often mouth open	Count 30 seconds while asleep, double it
Nail and pad color	Pink, refill under 2 seconds	Blue grey, refill over 3 seconds	Press a nail, release, count the pink return
Vocalizing	Silent or a short meow	Long scream that repeats every 20 to 60 seconds	Listen from the next room for 1 minute

4 things to do in the 10 minutes before the car

• Write the onset time down and take 1 photo plus a 10-second video of the cat trying to stand. Video of the drag pattern tells triage more than 5 sentences of description.
• Slide a rigid board, a tray or a folded blanket under the cat and lift both ends level. Do not lift by the scruff: a cat this sick has lost the reflexes that make scruffing safe.
• No massage, no heat pad, no aspirin, ibuprofen or acetaminophen. One tablet of a human painkiller is enough to cause liver failure or a stomach ulcer in a 4.5 kg cat, and the household toxin list covers the products owners reach for first.
• Keep the car at 22 to 24 C and call ahead with your arrival time, because a 15-minute drive with a screaming cat is 15 minutes of pain you can partly prevent.

What the ER will do in the first 90 minutes

Expect 6 checks in parallel: glucose, since under 60 mg/dL can mimic paralysis; potassium, since 2.5 to 3.0 mmol/L causes real weakness; 2 X-ray views for fracture; an echo for the hypertrophic cardiomyopathy found in most of these cats; a Doppler reading on each paw; and a pain score. Treatment opens with an opioid, oxygen if the breathing rate is over 40, and clopidogrel at about 18.75 mg per cat per day, the usual antiplatelet dose regardless of body weight. Expect 24 to 48 hours of manual bladder expression or a catheter, plus 2 to 3 checks a day.

Survival is 30 to 40 percent, and that is not a verdict

Roughly 30 to 40 percent of cats with ATE leave the hospital alive. The other 60 to 70 percent die or are euthanized, and most of those decisions land inside the first 24 to 48 hours. Two findings move a cat toward the better end: a pulse that returns within 6 to 12 hours, and a cat that stands with help inside 24 to 72 hours. Two push the other way: both hind legs cold and pulseless at hour 8, and congestive heart failure on the same echo. If the cat does go home, most vets quote a 3 in 10 to 4 in 10 chance of a second clot within about 12 months even on clopidogrel, which is why the 3-month recheck exists.

The first 6 weeks at home

Crate rest runs 4 to 6 weeks in a 90 by 60 cm pen with a 5 cm foam pad. Physio is 3 sessions a day of 5 minutes: 10 circles per leg, 10 stretches, 2 to 3 m of sling walking. Clip nails every 10 to 14 days, because a dragging toe wears skin through in days, and check the top of both hind toes every 48 hours for a 1 cm red patch.

When it is not a clot

A 1.5 m fall, a car impact at 30 km/h or a hard tail pull can fracture the pelvis or tear the nerves at the tail base, and those cats are usually incontinent from day 1 and sore over the spine. A disc extrusion builds over 6 to 24 hours, often starting with 1 leg. Tick paralysis, botulism and low potassium climb over hours or days rather than arriving in 10 minutes. If the cat is still bearing weight and hopping, run the gentler checklist in hind leg weakness before you assume the worst, and if only a front paw is involved, that is a separate problem covered in front leg limping. None of this is a reason to wait.

5 steps for the next hour

1. Note the exact minute the cat went down and write it on the carrier.
2. Press the groin for 10 seconds per side, then check nail color on all 4 paws.
3. Call the nearest 24-hour hospital and say paralysis, cold pads, no pulse, plus your arrival time.
4. Move the cat on a rigid board, hold the car at 22 to 24 C, and give nothing by mouth.
5. Ask 3 questions on arrival: is there a pulse, what is the potassium, and what does the echo show.

Frequently asked