A subungual hematoma is a condition in which there is bleeding under the fingernail or toenail. Usually caused by a crush injury, a subungual hematoma can cause symptoms such as intense pain and throbbing as blood collects under the nail.
Unless there are also broken bones or damage to the nail bed and/or surrounding tissues, a subungual hematoma is seldom worrisome.
Causes of a Subungual Hematoma
Most often, a subungual hematoma is an immediate consequence of a crush-type injury involving the tip of the finger or toe. Common examples include:
- Slamming your finger in a car door or house door.
- Hitting your finger with a heavy object such as a hammer.
- Dropping a heavy object such as a dumbbell on your toe.
- Stubbing your toe on a hard surface.
In some cases, a tumor under the nail can cause a darkened area that can resemble a subungual hematoma. If you have a darkened area under a nail, and no history of trauma to the nail, you should have it evaluated by your health care provider. The spot will grow out with the nail if it is a subungual hematoma. It will stay in the same spot under the nail if it is a tumor.
Symptoms of a Subungual Hematoma
The most common symptom of a subungual hematoma is severe, throbbing pain generated by the pressure of blood collecting between the nail and the nail bed. Other symptoms include:
- A dark-colored discoloration (red, maroon, or purple-black) under all or part of the affected nail.
- Tenderness and swelling of the tip of the affected finger or toe.
Diagnosis of a Subungual Hematoma
If a subungual hematoma was caused by a severe blow to a finger or toe, either seek immediate medical attention from your health care provider or go to an emergency room. In addition to the hematoma, you may have broken bones or serious damage to the nail bed and/or surrounding tissues.
The health care provider will examine your nail and you’ll likely undergo an X-ray to either confirm or rule out a bone fracture or other injury.
Treatment of an Uncomplicated Subungual Hematoma
A painless and small subungual hematoma usually requires no treatment. However, the pressure generated by pooled blood under the nail can be extremely painful. To relieve the pain, your health care provider may perform decompression, also called trephination, which allows the underlying blood to drain, relieving pressure and pain to the area.
After numbing the affected finger or toe with a nerve block, your health care provider may use one of the following decompression methods to drain the subungual hematoma:
- Cautery. A heated wire (electrocautery device) or carbon laser is used to burn the hole or holes. This is a quick and painless procedure.
- Needle. A large-diameter needle is used to perforate the nail.
During the cautery procedure, the heated tip is cooled by contact with the hematoma, which prevents injury to the nail bed.
After a decompression procedure,your nail will be bandaged. You will need to keep the finger or toe bandaged and elevated -- and use cold compresses, if necessary -- during the first 12 hours following decompression. In some cases, your health care provider may recommend you use a splint for as long as three days until the tenderness subsides.
The main complication associated with decompression is a small risk of infection in the residual hematoma.
Treatment of a Complicated Subungual Hematoma
If a subungual hematoma affects a large portion of the nail surface, the nail bed is likely to have significant injury. In these cases, nail removal may be necessary, along with stitches to the nail bed.
Resolution of a Subungual Hematoma
Unless a subungual hematoma is very small, an affected nail will usually fall off on its own after several weeks because the pooled blood has separated it from its bed. A new fingernail can regrow in as little as eight weeks while a new toenail may not fully regrow until about six months. If there has been injury to the nail bed and/or surrounding tissues, regrowth may be delayed.
Even with the best repair, there is still a possibility that the new nail may grow back with an abnormal appearance. See your health care provider if you notice any problems with the nail as it heals and regrows.