A sudden painful or paralyzed hind leg, cold paws, or fast, labored breathing in a cat can signal a life-threatening blood clot. Seek emergency veterinary care immediately; do not wait to see whether the signs improve. Aneurysms—abnormal enlargements and weakening of blood vessel walls—are rare in cats, but can also be dangerous if they bleed or contribute to a clot.
What blood clots and aneurysms mean in cats
A thrombus is a clot that forms in a blood vessel or the heart. If some or all of it breaks free and travels through the circulation, it is called an embolus. A clot can obstruct blood flow where it forms or lodge elsewhere, sometimes cutting off the supply of oxygen to tissue.
As an Amazon Associate I earn from qualifying purchases.
An aneurysm is an enlargement of a blood vessel caused by weakness in its wall. A damaged inner lining may encourage clot formation. The Merck Veterinary Manual describes aneurysms as rare in cats. They may cause no obvious signs unless bleeding or a related clot occurs.
What signs require emergency veterinary care?
Sudden hind-leg pain, weakness, or paralysis
A clot lodged where the aorta branches toward the hind legs can cause an aortic thromboembolism, often called a saddle thrombus. Signs may include sudden pain, weakness or paralysis in one or both hind legs, and limbs that feel cold. A partial blockage may cause less severe weakness or neurologic signs. Other arteries can be affected, so signs vary with the location of the obstruction.
#1 Best Overall
- ENSURE PET SAFETY ON THE GO with our dog travel accessories, dog must haves in pet travel. Our comprehensive pet first aid kit for dogs is your companion for worry-free journeys.
- VET ENDORSED: Our Dog & Cat first aid kit, vet-reviewed for precision, is expertly crafted in a medical facility, providing superior quality emergency dog essentials for peace of mind.
- PET EMERGENCY ESSENTIALS: In addition to comprehensive pet first aid supplies, we include dog muzzle, tick kit, emergency flashlight, and a handy mini first aid kit pouch.
- Pet Care Guide: A comprehensive first aid manual with essential instructions for treating everything from snake bites to minor injuries, making it dog must haves for your pet’s hiking and camping gear
- GEAR UP FOR OUTDOOR FUN! This first aid kit is your first line of defense during activities like hiking, jogging, or camping, designed for dog camping gear and hunting dog adventures.
Fast or difficult breathing
A clot in the lungs may cause a sudden increase in breathing rate or difficulty breathing. Some cats may cough up blood or bloody mucus. Breathing distress can also have other serious causes, including heart failure, so it needs urgent veterinary assessment rather than a home diagnosis.
Cornell Feline Health Center states that “Rapid/labored breathing and/or sudden paralysis are considered medical emergencies that must be addressed immediately.” If either occurs, contact an emergency veterinarian and arrange prompt transport.
Rank #2
- 1. BE PREPARED FOR ANY PET EMERGENCY – Vet-approved dog & cat first aid kit with pet-safe medical supplies, perfect for home, car, and outdoor adventures. Designed for fast, effective emergency care.
- 2. MORE THAN JUST BANDAGES – Includes vet-wrap, tick remover, first aid pads, saline wash, styptic pencil, slip leash & thermal blanket—real pet essentials, not just human first aid items.
- 3. BUILT FOR TRAVEL & ADVENTURE – Water resistant, hard-sided case protects supplies in your car, backpack, or RV. Ideal for hiking, road trips, camping, and disaster preparedness.
- 4. STEP-BY-STEP PET FIRST AID GUIDE – Easy-to-follow vet-reviewed manual for treating wounds, bites, bleeding, and emergencies—so you’ll always know what to do.
- 5. PET-SAFE & NON-TOXIC MATERIALS – Every item is vet-reviewed and made with pet-safe, non-toxic materials. Trusted by pet sitters, trainers, groomers, and adventurers—your pet deserves the best care!
Why cats develop clots
Clots are more likely when blood flow is restricted, a vessel lining is damaged, or a disease increases the tendency for blood to clot. Heart disease—especially cardiomyopathy with enlargement of the left atrium—is a major context for feline arterial thromboembolism. Clots can form in the heart and travel into the aorta or other arteries.
Other conditions associated with clots include hyperthyroidism and certain diseases affecting the lungs, kidneys, intestines, blood, or immune system. The Merck Veterinary Manual also associates pulmonary clots with heartworm disease, protein-losing kidney or intestinal disease, cancer, and immune-mediated hemolytic anemia. These associations do not establish the cause in an individual cat; a veterinarian must investigate the specific case.
Rank #3
- 1. BE READY ANYWHERE, ANYTIME – Lightweight, compact cat & dog first aid kit for hiking, camping, or travel. Designed for fast, effective emergency care when space and weight matter most.
- 2. PACKED WITH REAL PET ESSENTIALS – Includes vet-wrap, tick remover, cleansing wipes, saline wash, thermal blanket & more—no fluff, just field-tested dog emergency tools.
- 3. BUILT FOR BACKPACKING & ADVENTURE – Soft case fits in backpacks, glove compartments, or car consoles. Ideal for travel, hunting, road trips, camping, and everyday dog hiking gear.
- 4. STEP-BY-STEP PET FIRST AID GUIDE INCLUDED – Easy-to-follow, vet-reviewed manual covers injuries, bleeding, ticks, and emergencies—giving you the confidence to act quickly when it counts.
- 5. VET-APPROVED & PET-SAFE MATERIALS – All supplies are reviewed by veterinary professionals and made with non-toxic, pet-safe materials. Trusted by hikers, adventurers, and pet lovers.
How a veterinarian investigates a suspected clot or aneurysm
Testing depends on the signs, suspected location of the problem, and possible underlying disease. The veterinarian may use imaging and other diagnostics to assess both the obstruction and the condition that may have caused it.
- For suspected heart disease: Echocardiography (cardiac ultrasound) is Cornell’s stated gold standard for diagnosing feline cardiomyopathies. Chest radiographs can help assess congestive heart failure.
- For possible pulmonary clots: Chest radiographs may show changes associated with clots in the lungs, according to Merck.
- For a possible aneurysm: Merck notes that ultrasonography and angiography may help confirm the diagnosis.
- For screening when echocardiography is not immediately available: An NT-pro-BNP blood test may help identify cats that could benefit from further testing. Cornell cautions that this test does not definitively diagnose cardiomyopathy.
How blood clots and related conditions are treated
Treatment is individualized according to the clot’s location, how ill the cat is, and the underlying cause. For aortic thromboembolism, Merck describes pain relief and medication to reduce clotting. Clot-dissolving drugs are available, and surgery to remove a clot may be attempted in selected cases. Merck also notes that similar results may occur as the cat’s body breaks down the clot over time.
Rank #4
- Comprehensive Emergency Protection: RHINO RESCUE pet first aid kit provides comprehensive emergency preparation for your pet, containing gauze, self adhesive bandage, pet emergency tourniquet, ice pack, emergency blanket and other key first aid supplies to ensure effective initial treatment for your pet in emergency situations
- Supports Daily Care Needs: Equipped with a thermometer, toothbrush, feeding kit, poop bags with dispenser, muzzle, pill bag, water bowl, and disposable foot booties, this emergency bag can assist with daily pet care and feeding medications, helping you meet your pet's health needs
- First Aid Guide: The first aid manual is included to offer guidance for handling common pet emergencies, including heat stroke, trauma and bites. This manual provides helpful tips and steps to support you in staying calm and effectively responding to urgent situations
- Durable Materials Kit: The pet medical kit is made of abrasion-resistant fabric and two-way zippers design, which ensures that the gears remain dry and tidy in outdoor conditions. The interior features transparent dividers, making it easy to quickly access items in emergencies
- Compact & Portable: The entire pet kit measures 8.5 inches x 6.5 inches x 4.3 inches and weighs only 1.7 pounds. This hiking medical kit is designed to be portable, easy to go out, travel or camp, and convenient to provide your pet with basic first aid support wherever you go
If heart disease has caused congestive heart failure, possible veterinary treatments described by Cornell include oxygen, diuretics, and other cardiac medications. The veterinarian determines which therapies are appropriate and monitors their effects; medication and dosing decisions are not safe to make at home.
What recovery and prognosis can look like
The outlook after an aortic thromboembolism is often guarded. Merck reports that many affected cats die despite treatment or do not regain hind-limb function. Some cats that survive the initial crisis recover the ability to walk over several weeks, although lasting damage may remain.
Best Value
- Includes one 0.5 oz tub of Miracle Care Kwik Stop Styptic Powder; the Original styptic powder with Benzocaine for Pain Relief
- Your Pet Grooming Essential: Our styptic powder stops bleeding fast for dogs, cats, and birds; Specifically designed to act rapidly during grooming procedures to ensure a safe and enjoyable experience for your pets
- How to Use: Apply powder to a moistened cotton applicator to apply to the cut, nail, or other superficial bleeding area, applying moderate pressure for 5-10 seconds; Avoid use on deep wounds or body cavities
- From Nose to Toes We've Got Your Pet Covered: Our goal is to improve the human-animal bond by offering a complete line of innovative, solutions-driven products and accessories for animals, both small and large
- Trusted by Professionals: Miracle Care health and grooming products have been trusted and recommended by veterinarians and professional groomers for more than 40 years; Proudly Made in the USA in our Dayton, OH facility
In Merck’s account, cats with one affected limb generally do better than cats with signs in both limbs. Longer-term outlook often depends on the severity of the underlying heart disease. A veterinarian can discuss what these factors mean for an individual cat after assessing its condition.
How common is the heart disease linked to many feline clots?
Hypertrophic cardiomyopathy (HCM) is a common heart condition associated with clot risk, but estimates about HCM are not estimates of blood-clot or aneurysm rates. An ACVIM consensus statement published in 2020 estimated HCM prevalence at approximately 15% in the general cat population and reported prevalence of up to 29% in older cats. It also reported a five-year cumulative incidence of cardiac mortality of approximately 23% among cats with HCM in the studied context; that figure concerns cardiac mortality, not clot-specific risk.
Sources: Merck Veterinary Manual, “Blood Clots and Aneurysms in Cats – Cat Owners” (updated September 2024); Cornell Feline Health Center, “Cardiomyopathy” (updated March 2024); ACVIM consensus statement on feline cardiomyopathies (2020).
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsQuick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
