What is Hematoma?
Horses, by virtue of their loose skin and vascularized epidermal layers, are prone to forming hematomas. A hematoma is a collection of blood under the skin, similar in mechanism to a bruise, but the blood generally pools deeper in the tissues and is confined to one area, causing the swelling. The skin itself is not damaged, but the tissues and blood vessels underlying the skin are damaged, causing minor internal bleeding. Since the blood is confined to one area, it causes that area to swell out of proportion. Although most hematomas in horses will reabsorb back into the system, some require draining. Attempts to puncture and drain the hematoma should be made by a veterinary professional only as infections and complications can occur.
Also known as blood blisters, hematomas in horses can occur either within the muscle itself or between regions of connective tissue and may require draining or removal.
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Symptoms of Hematoma in Horses
The symptoms related to a hematoma are variable, depending both on the placement of the hematoma and its size. The most noticeable symptom is usually a soft lump somewhere on the horse's body which can become quite large. Some hematomas may cause unexplained bleeding, such as the ethmoid hematoma, which causes nosebleeds; other hematomas, like ovarian hematomas, may have no outward symptoms.
- Presence of a soft lump
- The lump may grow in size
- Asymptomatic is possible
This is a hematoma that arises on the pinna of the ear. Although common in dogs, cats, and pigs, this is an uncommon condition for horses.
This type of respiratory hematoma is unique to horses and is located in the paranasal sinuses. The smaller ethmoid hematomas generally start on the sinus floor, but the larger ones originate in the ethmoid structure itself.
Ovarian hematomas occur when an ovarian follicle fills with blood after ovulation. It can be differentiated from an ovarian tumor using ultrasound and only occurs when the mare is cycling.
When a hematoma develops from a bleed in the uterine artery it usually forms in the broad ligament. A small hematoma may cause only minor colic, but a larger hematoma could rupture and bleed into the abdominal cavity. The size of hematomas in this area can reach the size of a basketball.
Causes of Hematoma in Horses
More often than not a hematoma is caused by physical trauma to the area such as might occur when a horse experiences kicks, bites, or falls. The bodily harm may occur from fighting or play fighting between animals, but more often than not it is caused by something more mundane, such as bumping into a fence post or the bite of a horsefly on the ear. Although ethmoid hematomas may not reveal a direct cause, they are more common in middle-aged geldings than in other demographics.
Diagnosis of Hematoma in Horses
In most cases, hematomas are relatively distinctive. A collection of blood, sometimes combined with other bodily fluids and tissues, builds up either within the muscle or between regions of connective tissues. This leaves a large, fluid-filled swelling that can usually be both seen and felt on the surface of the skin. The blood in these lumps often separates out into blood clots and serum, and can be differentiated from an abscess that has not yet ruptured by the feel; an abscess will be much more firm to the touch than a hematoma and will generally cause the horse pain when it is palpated. In the case of internal hematomas, such as ovarian or uterine hematomas, diagnosis is usually achieved using ultrasound technology.
Once the hematoma itself is diagnosed, your veterinarian will evaluate the hematoma to determine whether it can be left alone to reabsorb into the body, or if it requires further treatment in the form of draining. Hematomas that may need draining include masses that have gotten overly large and pendulous, those that are interfering with natural movement, and those that are exhibiting signs of infection such as the area being hot to the touch, painful, or oozing pus.
Treatment of Hematoma in Horses
If you discover a new hematoma on your horse, the first step in treatment is to either ice or cold hose the hematoma for 15-20 minutes. It is best to do this as soon as possible so that it can both slow or even halt inflammation as well as constricting the blood vessels. In many cases, hematomas may be left on their own to reabsorb back into the body. This process can take some time, often a month or longer. Some veterinarians may choose to inject formalin directly into the mass to cause the blood clots to dissolve, making it easier for the body to reabsorb.
If the hematoma is overly large, if it appears to be infected, or if it is hindering the patient’s movement, the veterinarian may choose to lance the hematoma and let it drain. Certain types of hematomas, such as the ethmoid type of hematoma, require surgical removal to prevent facial distortion or necrosis of the bones that surround the hematoma.
Recovery of Hematoma in Horses
The prognosis for an equine hematoma depends on the placement and size of the swelling. In the case of ethmoid hematomas and hematomas caused by the uterine artery, the prognosis may be guarded even with veterinary assistance. The hematomas that are most likely to form, however, are on the chest, ribs, flanks, and haunches, and they have a fairly good prognosis. More often than not these lumps and bumps reabsorb back into the body without further intervention. If your horse is prescribed antibiotics because the hematoma has become infected, then it is critical that you complete the course to prevent reoccurrence.