What Causes Abnormal Bleeding in Cats

1 Overview

Abnormal bleeding in cats is also called coagulopathy, because it reflects a condition in which blood cannot clot. In cats, bleeding from a clotting disorder can occur in the skin, mucous membranes, tissues, body cavities, and various internal organs. When coagulopathy affects the membranes of the skin, mouth, nose, eyes, and external genitals, the bleeding is directly observable. With gastrointestinal bleeding, the cat may develop hematochezia (fresh blood in stool) or melena (dark, tarry stool). With urinary tract bleeding, you may observe blood directly in the cat’s urine, a condition called hematuria.

Abnormal bleeding can be mild or severe in cats, depending on the degree of blood loss. Bleeding from an accident or unknown cause requires timely diagnostic examination to determine whether a clotting abnormality exists. Many clotting abnormalities are serious because they can allow bleeding to progress until it becomes life-threatening.

Causes of Abnormal Bleeding in Cats

The causes of abnormal bleeding can be divided into: platelet abnormalities, blood vessel wall abnormalities, and clotting factor abnormalities. Platelets are small particles in the blood that form clots by aggregating at sites where the vessel wall is broken. Clotting factors are various protein components involved in blood coagulation; they are activated when a vessel bleeds, stick to platelets, and plug the leak in the vessel wall. Fortunately, these three types of clotting abnormalities are uncommon in cats.

Cause 1: Platelet Disease

Platelet disease occurs when platelet counts drop or platelets fail to function properly. Reduced platelet counts result from three causes: insufficient production in the bone marrow, destruction of platelets, or premature removal from circulation. Platelet dysfunction may be an inherited congenital condition or acquired later.

The following diseases cause reduced platelets:

1. Ingestion of drugs toxic to the bone marrow

2. Bone marrow infection by certain bacteria, viruses, and rickettsia

3. Immune-mediated destruction of bone marrow

4. Bone marrow cancer

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

The following diseases increase platelet destruction:

1. Immune-mediated platelet destruction (rare in cats)

2. Ingestion of certain drugs that damage platelets

3. Certain viral infections

The following diseases cause premature clearance of platelets from circulation:

1. Vasculitis

2. Certain parasitic infections

3. Certain spleen diseases

Diseases that affect platelet function include:

1. Congenital platelet dysfunction (feline Chediak-Higashi syndrome)

2. Certain drug poisonings

3. Certain infectious diseases

4. Kidney failure

5. Feline liver failure

6. Certain leukemias

Cause 2: Vascular Disease

Most vascular diseases cause abnormal bleeding by weakening the vessel wall. A smaller group of diseases cause bleeding by raising blood pressure, because when blood pressure rises high enough it can rupture the vessel wall and worsen bleeding.

The following diseases weaken the vessel wall:

1. Vasculitis – inflammation of blood vessels

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

3. Feline diabetes – sugar diabetes

4. Uremia – the diseased kidneys cannot clear waste in time

Cause 3: Clotting Factor Defects

Diseases related to clotting factor defects are as follows:

1. Hemophilia from inherited clotting factor deficiency (very rare in cats)

2. Warfarin-related products suppress vitamin K, and clotting factor activity depends on vitamin K. This is the most common cause of bleeding problems in cats. It occurs when a cat preys on rodents poisoned by warfarin products, or when a cat directly ingests softeners containing warfarin or similar toxins.

3. Liver disease that blocks clotting factor production

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