Blood clot formation in cats is a deadly condition that often strikes cats without warning. Understanding what causes blood clots is key to helping reduce the chances of your cat getting one. Our article today will explain what blood clots in cats are, how they affect a cat, how vets can treat them and how you can help prevent them.
Table of contents
Normal Blood Clotting
We all know that blood clots, or thrombi, are important following injury – how this normally works is as follows:
Clots form when there is damage to blood vessels, such as if you cut yourself. The damaged blood vessel releases chemicals to attract platelets, and narrows blood vessels to prevent excessive bleeding. These platelets stick to the damaged blood vessel and block the hole.
Over time a substance called fibrin binds to the platelets to help strengthen the clot. Eventually, the clot starts to break down revealing the repaired blood vessel wall underneath. Blood clots are key to prevent blood loss and prevent infection from entering the bloodstream.
Abnormal Blood Clotting
However, sometimes blood clots form where we don’t want them to. Small clots generally cause few problems but larger clots can get stuck in important blood vessels. This blocks the flow of blood and causes everything downstream to start to run out of oxygen and nutrients, as well as allow toxic products to build up. Restrict a tissue’s blood supply for too long and it will start to die. For comparison in humans, coronary heart disease is where the heart starts to die as fat build-ups block its blood supply. Luckily for fat cats out there, animals don’t tend to get coronary heart disease.
Aortic Thromboembolism (ATE)
However, what is far more common is a disease called aortic thromboembolism (ATE), also known as a saddle thrombus. This is where a blood clot blocks the descending aorta leading from the heart – the descending aorta supplies blood to the entire back end of the cat. If this supply is suddenly blocked, a cat can become paralysed on its back legs. The leg muscles will be very cold and painful, lack a pulse, and the nails and feet may turn blue. The cat generally will be quite distressed, have a fast breathing rate and may be fully collapsed. ATE is an emergency and the cat must be seen by a vet immediately. In some unfortunate cases, there may be no warning and the cat just suddenly dies.
Pulmonary Thromboembolism (PE)
Clots can also rarely block the blood vessels of the lungs, causing pulmonary thromboembolism (PE). Because the lungs are needed to reoxygenate blood, blocking their supply can cause a cat’s tissues to become deoxygenated body-wide. A cat with a PE may have blue gums, eyes and feet, be slow and collapsed and struggle to breathe. The clot may also cause them to cough up blood as well. PE is also an emergency.
Rarer still, blood clots can block other important vessels, such as those to the brain (causing a stroke), the kidneys (causing kidney disease), the front legs (causing paralysis) or other important organs.
All of the above blood clots can occur in dogs, but are generally much rarer except in dogs with heart disease.
Causes of Blood Clotting
By far the most common cause of blood clots in cats is heart disease. Most cats with heart disease get enlarged hearts – this causes the blood in the heart to swirl around more. We don’t know why but this promotes blood clot formation. As blood is pushed out the heart, clots dislodge and end up stuck in the descending aorta causing ATE, the lungs causing PE, or elsewhere.
Cats with heart disease often show symptoms such as weight loss, slowing down, difficulties breathing, or a potbelly. These symptoms can be used to diagnose heart disease and help prevent blood clots from forming. However, many cats are only diagnosed with heart disease after presenting as an emergency with blood clots – cats are remarkably good at hiding how sick they are.
Less common causes include those that promote a hypercoagulable state (increased likelihood to form clots), such as an overactive thyroid gland, low protein in the blood, heartworm, pancreatitis, sepsis and immune-mediated haemolytic anaemia. With these conditions, the blood is ‘stickier’, which promotes blood clot formation. As above, the clots can dislodge and get stuck in critical blood vessels, often the descending aorta. Many of these diseases will also have underlying symptoms but may also only be diagnosed after a blood clot emergency.
How We Diagnose and Treat Blood Clots in Cats
Vets often diagnose cats with blood clots brought in for emergency collapse – ATE is usually fairly obvious based on the cold and painful back legs. PE can be trickier to diagnose as it looks similar to other causes of respiratory distress. If a specific diagnosis is required, detecting no pulse in the limbs or taking a blood sample from affected legs can indicate it is ATE. Often, ultrasound will be used to confirm underlying heart disease, if not already known.
Usually, there is no time for an extensive diagnosis, and treatment must instead be immediately offered. To stabilise the cat, oxygen and fluid therapy are given. These are important to raise the blood pressure and try and help oxygen reach the rest of the tissues. As blood clots are very painful, strong pain relief is given as well. Underlying heart disease can start to be treated with diuretics to shift excess fluid, and medication to improve the heart’s rate and contractions. Manually moving the paralysed legs can sometimes help restore blood flow, in conjunction with other treatments.
The clot itself is sometimes broken down with anti-clotting medication. However, these are not always effective and can increase the risk of dangerous haemorrhage. PE may be helped with bronchodilators to widen the airways. Treatment of blood clots takes time, strict cage rest and monitoring, so the cat will have to stay at the vets for a while until the clot has broken down and the cat is stable enough to go home.
The likely outcomes
Unfortunately, even with treatment severe blood clots in cats, especially ATE and PE, do not carry a good prognosis. If the paralysis is severe, a vet may instead advise you to put them to sleep to prevent further suffering. This will also be the case if a cat is still painful despite treatment. Avoiding suffering is the most important thing a vet can do for a cat, and sometimes this may mean having to say goodbye.
Difficulties walking or even long-term paralysis are possible even with successful treatment. Furthermore, even if one clot is successfully treated, many cats will get clots again.
Preventing Blood Clots
As we mentioned above, many of the underlying causes of blood clot formation in cats can go unnoticed for months or years. If your cat starts to do anything abnormal, lose weight, slow down or struggle to breathe, we urge you to visit your vet for a checkup. On top of this, it is a good idea for your cat to have a regular checkup anyway, as vets can often spot subtle signs that could indicate disease. The earlier a disease is spotted, the better the prognosis and the more likely it is we can prevent blood clot formation. It is important to treat heart disease in particular to prevent clots.
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Discussion
I just lost my little boy Benchie to an Aortic Thromboembolism today. I wish I’d known the signs ahead of time, hindsight is 20/20 and looking back maybe I could have seen the signs, but after leaving him in the morning I came home to him collapsed and already with no feeling in his legs. The vet said he was critical by the time I got him there and there was little chance to save him. It makes me feel slightly better to know this is something of a common thing and not something where I screwed up and caused it, but it still hurts to lose my little buddy after almost 13 years with him.
my beloved Blu, our first tuxedo cat, just died today. i was in the kitchen and heard what i thought our cats playing in our bedroom. when i went up to get the cloth together for to be washed, he was laying next to our desk, like he is doing a lot of other times, but suddenly i saw him moving to the door the behind legs dragging. When i picked him up he was painting heavy. that is never a good sign. my son was home, its was his day of, so we dressed really fast, and he drove me with Blu to the emergency vet. Blue was so much in pain that he bit into the car door and the towel, i had wrapped around him. he bit me as well , but not as hard and he seemed to realize that he hurt me because he let go when I voiced my pain. They took him straight in and after a while we were called into the normal treatment room. the Vet said he has a blood clot they did some test, there was no blood flow to his behind legs, and he had heart disease. she said the prognosis was not good. even with intensive treatment, like staying for some days at the clinic, the danger that he would get more blood clots were high. he would have to see a heart specialist that would give him medicine for his heart. But his life expectancy was not good, she couldn’t say if he would be able to walk again. and she was worried that Blue would get into cardiac arrest. i asked him what she would do if it was her cat, and she said she would not let her cat suffer. My husband rushed to the vet from his work, and we all three made the heart wrenching decision to have him euthanized. i was in Schock. no sign of trouble, no losing weight or not showing interest in his surrounding before this happened. he was maybe 8 to 10 years old. My daughter found him 8 years ago ,dumpster diving and brought him home. my husband made the decision to keep him and named him Blu, since i was in Germany at that time visiting my family. he was a gentle cat, not very vocal. he always wanted to clean the area were their food dishes were, trying to bury their food. he snuggled up often to us or to his cat brother. loved to drink fresh water out of the bathtub. and loved the outdoors, which he could only visit with our supervision. he was very daring and snug downstairs at night , were or very controlling aggressive little dog is having her dominion. i questioned our decision, but after reading this article , i have more peace about it.
I just lost my 1 yo male kitty to blood clot that paralyzed both his legs, were cold, no pulse – he was fine the whole day – came home from the store and he was laying on the basement floor – crying/howling – so sudden – he was my shadow and my love – followed me everywhere – vet was very kind, but told us there was nothing that could be done & couldn’t even properly say goodbye – he was so distressed that he bit me, my husband and the vet – so heartbroken – he left his sibling sister and us way too soon 🙁
I had no idea about any of this until my cat suddenly collapsed and died on the way to emergency. He was only 2.5 years old. We were devastated. Now that I know I’m
Investigating, foods medications, and making sure my other kitties are seen regularly by our vet even if they never leave the house.
Our 2.5 year old cat died suddenly yesterday. One minute he was playing and then the next he collapsed and died. We did CPR and rushed him to the ER but he was already gone. Our family is heart broken. They told us he threw a clot and it stopped his brain function. Now I am learning everything I can about the “why”.
My nine year old kitty lost the ability to walk on his front leg. It also felt cool he was diagnosed as having a clot in the brachial plexus. He was just diagnosed with a murmur, arrhythmia and HTN. We are heartbroken.
May 24,2023 my son woke up this morning freaking out about our sphynx cat Cooper not being able to move his back legs and crying,within an hour we were at the vet. He had his teeth removed on April 27th 2023 for gum disease to prolong his life and make him feel better over all. It went great and without incident. Vet said his heart was well for the teeth removal and less then a month later we are mourning the loss of our most loved pet. His hind legs showed no pulse by the time we got to the vet and his pain level was undeniable. He was put to sleep within an hour and i just ache so much and just don’t understand how an active fun animal can turn so quickly. Its not fair.
My cat was running around jumping and active and all of a sudden he couldn’t move his back legs and died, I don’t understand, just the other day he was so active and loved being petted, now He is gone!
It’s awful isn’t it.
Sadly, while there are lots of things that we know can trigger a blood clot, sometimes they come out of nowhere and we never really know why.
I am so sorry for your family’s loss.
We just lost our beloved Lucy, on Friday May 12th. She was almost 15. It was sudden as we didn’t know she had a heart murmur, and that is what they said caused the blood clots, one to her hind legs and one to her brain, it happened at home and we are devastated. We rushed her into the ER Vet since it was almost midnight, and we had to put her to sleep. It still doesn’t feel real, the grief is so intense. I miss her so much. 🙁
I have lost two cats this way, an otherwise healthy eight-year-old male years ago and then my 19-year-old female just last week. In both cases sudden and devastating and requiring immediate euthanasia. I am still a mess. The poor sweet kitty, my best friend for almost two decades.
I am so sorry to hear this. We lost our 8 year old kitty 2 years ago, very suddenly and now our oldest boy, aged 14 has been diagnosed with a clot. He is on blood thinners and we are praying.
Hi there, I was researching about blood clots in cats because my cat suddenly has one. She lost feeling in her back legs and is in so much pain. I was just wondering if the blood thinners helped your cat? The vet told me they never work..so I don’t know what to do, its awful.
In my experience, they very occasionally do work, although usually when the clot is only in one leg.
The problem is the amount of pain the cat has to go through before circulation can be restored, and the loss of tissue in the limb.
Our 11-year-old Frisky passed away from blood clot formation on Jan 31, 2023. We were told when he was 1 year old he might have a heart murmur but according to the vet, it was mild and not too much of a concern. He was a healthy and very active cat until the last minute. he came to sleep on my chest the night before around 11.30 Pm. In the morning around 3.30, he was crying in distress and I woke up to find out that his back legs were paralyzed and he was in pain. we took him to the emergency right away where he has diagnosed with a blood clot. Unfortunately, we had to say good buy to him. It was heartbreaking and we miss him so much. Oh Frisky, you gave us Joy and happiness throughout your entire life. We love you Frisky.
Sadly, our 11 1/2 year old cat Dobby passed away from this on Monday. My wife and I are still in shock. Sunday evening, he was playful, he was eating, he was doing everything he normally does. He had CKD for a couple of years now, but his levels were never too bad and he seemed to be doing fine. No one ever mentioned to us the possibility of heart disease. Then Monday morning at 5 a.m., my wife woke me up to tell me that he couldn’t move his back legs at all and was dragging himself around. We met our vet when they opened (for inexplicable reasons, the emergency vet in town didn’t want to see him). We were told the diagnosis and his outlook at around 8:30 a.m. and we were going to get a second opinion before making the decision whether to hospitalize or euthanize, when at 10:00 a.m. a second clot lodged in his lungs and the decision was taken out of our hands. We had no choice but to put him to sleep and end his suffering. We’re both having a hard time dealing with this and our other two cats were very close to him as well and they are starting to wonder what happened to him. I sure do miss my little buddy, Dobby. I fear it will be a long time before we all recover from this. We love you, Dobby and everybody misses you.
I discovered my 13 year old Cat Cous at 5am on Monday in the same condition.I too couldn’t see an emergency Vet in town.I got the appointment for 9am and was told there was treatment though it didn’t always work.My Cat had had thin blood all his life and through all other advice I refused euthanasia.Believing the steroids would pull him though.So in the last 6 months he was on them all the time.Then I had to vary the amount as they too could have harmful effects on his life.The Aneurysm of the Spne hit him out of the blue.He was in good form the week before but was showing disinterest in his renal diet of Chicken.I gave him a full steroid he hadn’t had any for 5 days.He perked up and felt better in the morning.Though there was a lot of vomiting over the last 3 weeks and it wasn’t looking good.I can’t be sure if I did my little companion an injustice or a favour.He was peaceful after sedation and me and my girlfriend spoke to him As he gently went.If he hadn’t had the steroid problem I would have tried Hospitalization.I didn’t want him to suffer anymore and now I’m upset.They bring so much happiness and also grief.
My beloved Mystic never showed any signs. Eight and a half years, never sick a day in his life. While doing laundry I turned as he was dragging himself out of the litter box. His left leg was cold as I wiped ruin off. I actually felt the wipes, thin they sure feel cold today. We wrapped him up and the emergency animal hospital said his heart had the blood swirling around. She said he wouldn’t regain use if his legs and he was in pain. I am still in shock and mourning. His twin brother is beside himself. Three weeks later, I am still dismayed. Thanks for reassuring me that putting my baby, who was in pain, to sleep was the only choice. I’ll have a time with Magic, but we’ll all get through it, together.
I want to believe this is what happened to my cat. He was only 1 year old and I lost him due to heart and respiratory issues. I didn’t really understand what the vet was telling me because I was so distraught about my son. This article really broke it down for me so I have an idea of what happened. He was never really that playful, which I thought was his personality, and he never really gained weight even thought I really tried. My vet told me that he was suffering, it was the hardest thing I’ve had to do but I know he’s not in pain anymore.