Hematoma

Hematoma, in medicine, pool of blood trapped in an area of the body outside of a blood vessel, such as under the skin, in an organ, or in a cavity between organs. A hematoma is usually the result of an injury that breaks the wall of a blood vessel, causing blood to pool in the surrounding tissue. Unlike the blood in a bruise, the blood in a hematoma is usually clotted or partly clotted.

Hematomas can occur in various parts of the body, and their symptoms and severity depend on their location. Hematomas under the skin or nails can be caused by minor accidents, such as bumping into a hard surface or hitting the fingernails with a heavy object. A hematoma under the skin, called a subcutaneous hematoma and popularly known as a blood blister, results in a hard, painful bump that changes color over time as the body breaks down the clotted blood. A hematoma that occurs in the outer ear is called a hematoma auris or, sometimes, cauliflower ear, and leads to a painful, bulging malformation of the outer ear. Subungual hematomas, which occur under a fingernail or toenail, cause the affected nail to turn black and, occasionally, to fall off. Generally not serious, these hematomas usually go away on their own as the broken blood vessel heals and the body breaks down and reabsorbs the clotted blood. The clotted blood is not within a blood vessel, so there is no danger that the clot will travel to the lungs and obstruct vital blood vessels there. Nevertheless, these hematomas may be uncomfortable and physicians sometimes drain them, using a needle and syringe.

Hematomas in the brain and spinal cord are more dangerous. They are usually the result of a serious injury, such as a car accident or a fall from a high place. Often these hematomas are caused when sharp, fractured bones tear the walls of nearby blood vessels. A hematoma between the two membranes that cover the brain is called a subdural hematoma, and a hematoma between these membranes and the skull is an epidural hematoma. Signs of a subdural or epidural hematoma include severe headache, drowsiness, loss of consciousness, loss of strength or feeling in part of the body, seizures, and slurred speech after a head injury. Adults with an epidural hematoma may lose consciousness temporarily and then experience a lucid period in which they regain full intellectual functioning before their symptoms worsen again.

A hematoma in the brain or spinal cord requires immediate medical attention because the pooling blood may press on vital areas of these organs, leading to brain damage or even death if left untreated. Doctors use computed tomography (CT scanning) or magnetic resonance imaging (MRI) to diagnose these hematomas and pinpoint the exact location of the pooled blood. Brain and spinal hematomas often require emergency surgery to drain the pooled blood, locate its source, and stop the bleeding.

Elderly people may develop a hematoma in the brain from a relatively minor injury—such as a bump on the head—because as people age their veins become fragile and more easily injured. Children’s veins, in comparison, are strong and elastic, and a brain hematoma in a child is unusual and may be a warning sign of child abuse. Certain medical conditions—including blood clotting disorders, such as hemophilia, and the autoimmune disease systemic lupus erythematosus—can make an individual more susceptible to hematomas in various parts of the body.