A hematoma is a localized pocket of blood that collects outside a blood vessel, typically after some kind of injury, irritation, or bleeding disorder. In cats, the most common version by far is the aural hematoma, a fluid-filled swelling on the ear flap that can balloon up alarmingly fast. But hematomas can also develop in less visible places like the spleen, around the kidneys, under the skin, or in the limbs, and those cases tend to be more medically complex and harder to spot.
Ear Hematomas Are the Type You’re Most Likely to See
If your cat develops a hematoma, there’s a strong chance it’s on the ear. An aural hematoma shows up as a soft, puffy, sometimes warm swelling on the pinna (the floppy or upright part of the ear). The ear flap fills with blood between the skin and the cartilage, making it look swollen and pillow-like. Cats often hold the affected ear at an odd angle or paw at it, and you might notice the ear feels heavier than normal when you touch it.
The underlying sequence is pretty straightforward. Something irritates the ear, the cat responds by scratching or shaking its head vigorously, and that repeated trauma ruptures small blood vessels inside the ear flap. Blood pools between the layers of cartilage, and because the space is relatively enclosed, it doesn’t drain on its own. Once the pocket forms, even mild continued scratching keeps the bleeding going and prevents the body from reabsorbing the fluid.
What Triggers an Ear Hematoma
The hematoma itself is a secondary problem. The real issue is whatever made the cat shake or scratch so aggressively in the first place. In cats, aural hematomas are less common than in dogs and are frequently linked to ear mites (specifically Otodectes cynotis) or otitis externa, an infection or inflammation of the outer ear canal.1PubMed Central. Aural hematoma and it’s treatment: A review Ear mites are especially common culprits in younger cats and multi-cat households, where the mites spread easily from one animal to another.
Other triggers include allergic skin disease, foreign bodies lodged in the ear canal, and polyps or growths inside the ear. In some cases, a cat with an underlying bleeding disorder may develop an ear hematoma from relatively minor head shaking that wouldn’t cause trouble in a healthy animal. That’s an important distinction because treating the hematoma without addressing the root cause almost guarantees it will come back.
How Vets Treat Ear Hematomas
Small ear hematomas sometimes resolve on their own, but the result is usually a permanently crumpled, thickened ear, often called a “cauliflower ear.” Most vets recommend active treatment both for the cat’s comfort and to preserve the ear’s shape.
The standard surgical approach involves making an incision on the inner surface of the ear flap, draining the blood and any clots, and then placing a series of sutures through the ear to hold the skin flat against the cartilage and prevent the pocket from refilling. These sutures are usually arranged in a quilting pattern that runs parallel to the length of the ear.2PubMed Central. Aural hematoma and it’s treatment: A review Some surgeons use a small drain or cannula instead of (or alongside) sutures to allow continued drainage as the tissue heals.
Non-surgical options exist as well. Needle aspiration, where a vet draws the blood out with a syringe, is quick but has a high recurrence rate because the pocket just fills up again. Steroid injections into the hematoma cavity aim to reduce inflammation and discourage re-accumulation, and some vets combine aspiration with steroid therapy for a middle-ground approach. These less invasive methods tend to work better for smaller hematomas caught early.
Regardless of the method chosen for the hematoma itself, the underlying ear problem needs to be treated at the same time. If the ear mites or infection driving all that scratching aren’t addressed, the cat will keep traumatizing the ear and the hematoma will recur.
Bandaging and Recovery After Ear Treatment
Post-treatment bandaging plays a bigger role than many owners expect. A bandage protects the ear from further self-inflicted damage, keeps the skin pressed against the cartilage so the layers can heal together, and shields any incision or drain from contamination.3Veterinary Clinics of North America: Small Animal Practice. Surgical Diseases of the Ear The bandage also provides a way to secure drains or tubes in place if they were part of the procedure.
How long the bandage stays on varies. The general guideline is to keep it in place until drainage has slowed significantly or enough granulation tissue has formed to hold the ear together. Most cats tolerate an ear bandage reasonably well, though an Elizabethan collar (the cone) is often needed simultaneously to stop the cat from pulling the bandage off. Expect the full healing process to take a few weeks, with one or more bandage changes along the way.
Hematomas in Other Parts of the Body
Ear hematomas get the most attention because they’re visible and common, but blood can pool in other locations too. These internal or deep-tissue hematomas are less frequent, harder to detect, and sometimes more dangerous.
Splenic Hematomas
The spleen is one of the organs where hematomas occasionally develop in cats. They can result from blunt trauma, a bleeding disorder, or in some cases form alongside a tumor. On ultrasound, a splenic hematoma can look complex and mimic both benign and cancerous masses depending on how old the blood collection is. The key distinguishing feature is that hematomas tend to shrink over time, whereas tumors generally grow.4PubMed Central. Feline abdominal ultrasonography: What’s normal? What’s abnormal? The spleen In a large study that looked at splenic disease in over a hundred cats, hematoma was among the rarer findings, appearing in only one of 101 cases, compared to much more common diagnoses like lymphosarcoma and mast cell tumors.5PubMed. Ultrasonographic appearance of splenic disease in 101 cats
That rarity is itself useful information. If your vet spots a mass on your cat’s spleen, a hematoma is possible but far less likely than a tumor. Repeat imaging over a few weeks can help distinguish the two: a shrinking mass points toward a hematoma, while a growing one raises more serious concerns.
Kidney and Abdominal Hematomas
Hematomas in or around the kidneys are uncommon but can develop in specific circumstances. One documented scenario involved a cat with a ureteral stone that partially blocked urine flow, leading to increasing pressure in the kidney. The renal pelvis eventually ruptured, causing an intrapelvic hematoma and bleeding into the space around the kidney. The cat required surgical removal of the affected kidney and ureter, and recovered well over the following months.6PubMed. Renal pelvic rupture, intrapelvic haematoma and retroperitoneal haemorrhage associated with obstructive ureterolithiasis in a cat Cases like this are rare but illustrate how blockages or injuries to internal organs can set the stage for blood to collect in unexpected places.
Limb and Subcutaneous Hematomas
Cats can also develop hematomas in the soft tissue of a limb, under the skin, or at injection sites. These often look like a firm or fluctuant swelling and are typically caused by blunt trauma, a fall, or occasionally a medical injection that damages a small blood vessel. Most are minor and resolve on their own with rest, but some can become complicated.
When a Hematoma Points to a Bigger Problem
A single ear hematoma in an otherwise healthy cat with an ear mite infestation is usually a straightforward problem. But when hematomas appear in unusual places, recur without an obvious trigger, or show up alongside other signs of bleeding, the concern shifts to systemic disease. Two scenarios in particular deserve attention.
Anticoagulant Rodenticide Poisoning
Cats that ingest rat or mouse poison, or eat a rodent that was poisoned, can develop a severe bleeding disorder because these products work by blocking the body’s ability to form blood clots. In a case series of seven cats with suspected anticoagulant rodenticide poisoning, the animals presented with a range of bleeding signs including hematomas, bleeding from the ears, blood in the stool, and tiny skin hemorrhages called petechiae.7PubMed Central. Haemorrhage in seven cats with suspected anticoagulant rodenticide intoxication In another case, a six-month-old cat developed a large hematoma over the top of her skull that had been progressively swelling for four days. The owner eventually revealed that the cat had access to multiple brodifacoum bait stations, a common second-generation rodenticide.8PubMed Central. Successful autologous transfusion from the subcutaneous space in a domestic shorthair cat with suspected anticoagulant rodenticide toxicity
Rodenticide poisoning is a veterinary emergency. If your cat develops unexplained swelling or bruising and there’s any possibility of exposure to rat poison, even secondhand through a rodent, get to a vet immediately. Treatment involves vitamin K therapy to restore clotting function, and some cats need blood transfusions if the blood loss is severe.
Hypertension and Clotting Disorders
Older cats with chronic kidney disease or hyperthyroidism frequently develop high blood pressure, which can contribute to bleeding events in various organs. One reported case involved a 14-year-old cat whose blood pressure was severely elevated. The cat presented with an eye bulging forward, third eyelid protrusion, and severe retinal hemorrhage in both eyes. Imaging revealed a suspected blood clot behind the right eye.9PubMed Central. Retrobulbar thrombus in a cat with systemic hypertension While a thrombus (clot) is technically distinct from a hematoma (pooled blood), both reflect vascular problems that share underlying risk factors. Cats with uncontrolled hypertension are more vulnerable to spontaneous bleeding and blood pooling in tissues throughout the body.
Inherited or acquired clotting factor deficiencies, liver disease, and certain cancers can also impair a cat’s ability to form clots properly, raising the odds of hematoma formation from even trivial injuries. If your vet discovers a hematoma and can’t identify an obvious trauma that caused it, blood work to evaluate clotting function and organ health is a reasonable next step.
Hematomas from Veterinary Procedures
It might seem counterintuitive, but some hematomas develop as minor side effects of routine veterinary procedures. A common example is cystocentesis, the technique where a needle is inserted through the abdominal wall directly into the bladder to collect a sterile urine sample. Studies in cats have found that small submucosal hematomas can form in the bladder wall after the procedure, though these typically cause no lasting problems and resolve without treatment. Other minor complications in the same category include small skin hematomas at the needle site and occasional blood clots inside the bladder, all of which tend to be self-limiting.10Juniper Publishers. Diagnostic and Therapeutic Cystocentesis in Dogs and Cats: Considerations
Intramuscular injections can occasionally lead to hematomas at the injection site as well, particularly if a blood vessel is nicked during the procedure. In most cases these small collections of blood are absorbed by the body within days and don’t need any intervention. The risk is low enough that it doesn’t change the calculation on whether to do these procedures, but it’s worth knowing about so you don’t panic if you feel a small lump at an injection site a day or two later.
When a Hematoma Won’t Go Away
Most hematomas follow a predictable arc: blood pools, the body gradually breaks it down, and the swelling resolves over days to weeks. But occasionally a hematoma refuses to cooperate. In one documented case, a five-year-old cat developed a hematoma in the right hindlimb after an intramuscular injection. The initial swelling resolved with conservative care, but it came back twice within a single week. When surgeons explored the area, they found a large cavernous lesion near the knee. Tissue analysis classified it as a chronic expanding hematoma, a rare condition in which the blood collection becomes self-perpetuating, with the body’s own inflammatory response to the old blood triggering further bleeding at the margins of the lesion.11PubMed Central. Chronic expanding haematoma in a cat
Chronic expanding hematomas are rare in cats, but they matter because they can be mistaken for tumors. The imaging appearance overlaps with soft-tissue sarcomas and other cancers, and even on physical exam the growing mass feels concerning. Definitive diagnosis usually requires a biopsy or surgical removal with histopathology to confirm the tissue is inflammatory rather than neoplastic. If your cat has a lump that has been growing slowly over weeks or months and doesn’t respond to conservative treatment, surgical exploration and tissue sampling are the clearest path to an answer.
Spotting Trouble Early
Ear hematomas are usually obvious. The ear looks wrong, feels squishy, and the cat is clearly uncomfortable. Internal hematomas are a different story. Because blood collecting inside the abdomen, around an organ, or deep in a limb doesn’t create the same visible signs, you’re more likely to notice vague symptoms: lethargy, reduced appetite, pale gums, or unexplained swelling. If your cat has had recent trauma, such as a fall from a balcony or a fight, even mild versions of these symptoms warrant a vet visit.
Imaging is the main tool for finding internal hematomas. Ultrasound is particularly useful because it can show the size, location, and echogenicity (basically the internal texture) of a blood collection, and repeat scans over time can distinguish a hematoma that’s shrinking from a tumor that’s growing.12PubMed Central. Feline abdominal ultrasonography: What’s normal? What’s abnormal? The spleen For bleeding disorders like rodenticide toxicity, blood tests that measure clotting times and platelet counts help pin down the cause and guide treatment decisions.
One practical note for cat owners: indoor cats that never encounter rodent bait and rarely experience blunt trauma are at lower risk for most types of hematoma beyond the ear variety. Keeping your cat’s ears clean, staying on top of parasite prevention (especially ear mites), and monitoring for signs of ear discomfort are the most actionable steps you can take. For outdoor or indoor-outdoor cats, knowing where rodenticide bait stations are placed around your property and keeping your cat away from them removes one of the more dangerous systemic triggers for abnormal bleeding.