Unusual Bleeding in Cats: Causes and Concerns

If a cat experiences gastrointestinal bleeding, it may develop hematochezia (fresh blood in the stool) or melena (dark, tarry stools). In cases of urinary tract bleeding, you might directly observe blood in your cat's urine, a condition known as "hematuria."

Abnormal bleeding can affect cats in varying degrees, from mild to severe, depending on the amount of blood lost. Bleeding caused by accidents or unknown reasons requires prompt diagnostic checks to determine if there are any clotting abnormalities. Many clotting disorders are serious because they can escalate bleeding to a lifethreatening level.

Causes of Abnormal Bleeding in Cats

The causes of abnormal bleeding in cats can be categorized into three main types: platelet abnormalities, vascular wall abnormalities, and coagulation factor abnormalities.

Platelet Disorders

Platelets are small particles in the blood that help form blood clots by clustering at the site of a vascular wall break. When platelet numbers are low or they don't function properly, platelet disorders occur. Here are some reasons for reduced platelet counts:

1. Insufficient production of platelets in the bone marrow.

2. Destruction of platelets.

3. Premature removal of platelets from the bloodstream.

Platelet dysfunction can be a congenital, inherited condition or a condition that develops later in life.

Diseases that can lead to reduced platelet counts include:

1. Ingestion of drugs toxic to the bone marrow.

2. Infections by certain bacteria, viruses, and rickettsiae.

3. Immunemediated destruction of the bone marrow.

4. Bone marrow cancer.

5. Myelitis and bone marrow fibrosis, where bone marrow cells scar and disappear.

Diseases that can increase the destruction of platelets include:

1. Immunemediated destruction of platelets (rare in cats).

2. Ingestion of certain drugs that damage platelets.

3. Some viral infections.

Diseases that can cause platelets to be prematurely cleared from the bloodstream include:

1. Vasculitis.

2. Certain parasitic infections.

3. Diseases of the spleen.

Diseases affecting platelet function include:

1. Congenital platelet dysfunction (Cat ChediakHigashi syndrome).

2. Drug toxicity.

3. Certain infectious diseases.

4. Kidney failure.

5. Liver failure.

6. Some leukemias.

Vascular Disorders

Most vascular disorders cause abnormal bleeding by weakening the vascular walls. A smaller number of diseases lead to bleeding by increasing blood pressure, as high blood pressure can cause blood to burst through the vascular walls, exacerbating bleeding symptoms.

Diseases that weaken vascular walls include:

1. Vasculitis – inflammation of the blood vessels.

2. Hyperadrenocorticism – a disease where the adrenal glands secrete too much cortisol (rare in cats).

3. Diabetes mellitus – a type of diabetes.

4. Uremia – when the kidneys fail to remove waste products in a timely manner.

Coagulation Factor Disorders

Diseases related to coagulation factor disorders include:

1. Hemophilia caused by a genetic deficiency of clotting factors (rare in cats).

2. Products related to warfarin that inhibit the presence of vitamin K, which is essential for the activity of clotting factors. This is the most common cause of bleeding problems in cats. It occurs when cats eat rodents poisoned by warfarin or similar toxins, or when they ingest substances containing warfarin or similar poisons.

3. Liver diseases that prevent the production of clotting factors.

4. Disseminated intravascular coagulation (DIC), which is widespread bleeding caused by the consumption of platelets and clotting factors.