Diagnosing and Assessing Swellings in Horses
Diagnosing and Assessing Swellings in Horses
by Robert N. Oglesby, DVM
Do you have a swelling under the skin and you are unsure what it is? This is the place to start.
Introduction
Article's |
Swellings are a very common problem in horses with many causes, as a result we have a number of different articles on this subject. This article is designed to explain the causes of swelling, help differentiate the various types, and then direct you to more specific topics on the specific swelling. Note that bumps, lumps, and tumors of the skin are discussed elsewhere. Some swellings are obviously part of the skin but if you are uncertain try moving the skin around the swelling. Does the swelling move with the skin or does the skin move over the top of it? If it moves with the skin most likely it is associated intimately with the skin and discussed in the article on skin bumps and tumors, ...for more information. In this article tumors and generalized swellings of the tissues under the skin are discussed. The differences between non-inflammatory and inflammatory swellings are outlined and the common swellings that occur in horses are identified by their characteristics and location. Links to more specific articles on further diagnostics, treatment, and prognosis are provided. |
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Is the swelling caused by inflammation?
The common swellings of the horse are often best understood by separating them into inflammatory and noninflammatory processes. So what is inflammation? It is the body's response to physical insults like trauma, infection, allergies, and autoimmune diseases. Inflammation results in serum (the liquid part of the blood) leaking out of the blood vessels and collecting in and around the tissues, which is why swelling is associated with inflammation. Inflammation is recognized by redness, heat, swelling, and pain. It is difficult to detect the redness of inflammation with the highly pigmented skin of most horses so swelling, heat, and pain are the hallmarks in horses.
Not all swellings are inflammatory. Noninflammatory swellings are no different in temperature than the surrounding non-swollen areas and are not painful. They are often chronic in nature and persist or recur under certain conditions. Very mild inflammation or early in the inflammatory disease process there may be minimal heat and pain so frequent reassessment is a good practice it uncertainty about the nature of the swelling exists.
The presence or absence of heat and pain are detected by careful exploration of the swelling. This is best done in a quiet and relaxed atmosphere. Horses often react when you touch and squeeze them even when not painful so first carefully evaluate for reaction by palpating non-effected similar areas. This gives you several benefits:
- You can observe the horses normal reaction to such an exam.
- You can observe the normal temperature of the area.
- It allows the horse to get use to this type examination.
After careful and thorough exploration you should be able to decide which description best fits your horse:
Is this swelling associated with edema?
After deciding whether your swelling is caused by inflammation the next step is to determine is it caused by edema. So what is edema. Our body contains a fair amount of fluid, outside of blood vessels, lymphatic vessels and the cells. This extracellular fluid bathes the cells and aids in the movement of nutrients and waste products. It also has important inflammatory components. When excess fluid accumulates between the cells and tissues it causes swelling. Edema is recognized clinically because it pits on firm pressure and then is slow to refill, taking 5 to 30 seconds.
There are many causes of edema, some inflammatory and some not. However by knowing whether or not the tissues are inflamed and by knowing whether it is edematous or not greatly decreases the number of possible causes of the swelling.
Cool, Nonpainful Swellings
CHARACTERISTICS |
POSSIBLE CAUSES |
COMMON DIAGNOSES |
Generalized Swelling In Lower Legs or Ventral Midline |
This is passive edema where fluid has become congested in the tissues and not associated with inflammation.
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Swelling Is Associated with a Joint or Tendon |
Mild inflammation or loss of elasticity of a synovial sheath like a joint capsule, tendon sheath, or bursa. If acute and unilateral may represent blunt trauma or miss-step. Trauma from repetitive over-stretching during work outs. |
For more on localization of these conditions and links to these diagnoses see images below. |
It feels like a tumor or cyst not associated with a joint or tendon. Well defined swellings that are soft to firm but don't pit or fell bone hard. |
Many normal and abnormal structures might fit this description so location and history important to define cause. |
For more on localization of these conditions and links to these diagnoses see images below. |
Hard Swellings on the Bone |
Bone responds to growth, stress, or bruising by laying down more calcium. |
For more on localization of these conditions and links to these diagnoses see images below. |
Warm, Painful, Swellings
Swelling, heat, and pain including lameness are signs of inflammation and proper treatment relies on accurately assessing the cause of the inflammation. Trauma, infection, allergies, and autoimmune diseases are all diseases that cause inflammation. If the swelling is warm you should take your horses temperature to see if there is a fever, ...for more information.
Fever is an important way we can differentiate infection from trauma. Trauma and irritants don't usually have fever while infection if remarkable enough does. However there are exceptions. First, many autoimmune diseases, where the body's immune system is attacking itself, have fever. If there is a lot of tissue destruction or if the pain is severe, trauma may present with a increase in temperature. Some infections also do not have fever, for instance well encapsulated abscesses may present as a tumor that is warm and painful but not have fever.
CHARACTERISTICS |
CAUSES |
COMMON DIAGNOSES |
Edematous but No Fever |
This is active edema that is associated with inflammation from trauma. The inflammation causes fluid and inflammatory mediators to escape from blood vessels into the inflamed tissues. |
Even when fever is not present infection should still be considered when the lesions are confined to a small area, the reaction is superficial like on the skin, draining well, worsening over time or multiple areas (like 2 legs) are effected:
For localization to a specific structure try the images below this section. |
Edematous and Has Fever |
This is active edema that is associated with inflammation secondary to either infection or autoimmune disease. The inflammation causes fluid and inflammatory mediators to escape from blood vessels into the inflamed tissues. |
If fever is present consider infection or autoimmune disease, if not present infection should still be considered in focal lesions that are worsening over time. For localization to a specific structure try the images below.
Legs with a generalized, hot, painful, swelling have a number of specific causes...for more information. For focal swellings see the images below for localization. |
Hot, Painful but Not Edematous |
Often these will be infection that is encapsulated in a joint capsule, tendon sheath, or walled off abscess. Note that in time the overlying tissues will usually become hot and edematous making diagnosis of the exact structures that are infected difficult. To find the underlying infection may require ultrasound. |
For localization to a specific structure try the images below. |
Warm, Nonpainful Swellings, Unsure if Inflammatory
If just minimally warmer than the surrounding skin and their is no pain or lameness consider this may be a transient nonspecific warmth and you should review the cool swellings above. If considerably warmer than the surrounding skin you should also consider the possibility you are looking at a early inflammatory problem that may worsen and has not become painful yet or possibly pain is not a prominent feature of the inflammation. An example of such a swelling would be a broken blood vessel that results in a hematoma or if it seems well encapsulated, a noninfectious abscess.
A further important differentiating factor is whether the inflammation is responsive to NSAID's. Irritants and non-infectious reactions are usually moderately to very responsive to their use. When uncertainty exists, particularly if there is pain or fever associated with the swelling, your veterinarian should be consulted. Further diagnostic work up may include ultrasound, tapping if fluid or biopsy if a solid mass.
Swellings by Location
Below are some of the common locations for swellings. Often just knowing the location, texture, and history allows you to diagnose the cause of the swelling but not always and exceptions always exist. See if you can match up your swelling with one of the locations below and decide whether it is inflammatory or not:
Common swellings around the head:
MAGENTA:
DARK GREEN:
LIGHT GREEN:
LIGHT BLUE:
RED:
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Common swellings on the body:
MAGENTA:
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Swellings in the upper front limb:
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Common swellings on the rear limb:
RED: Hard chronic swelling: bone spavin (osteoarthritis of the distal tarsal joints). |
Swellings in the lower limbs: |
Note: this article is meant to help you diagnose the problem with your horse and is not meant to take the place of veterinary care. If your horse is distressed you should consult your veterinarian.
For More Information:
- On this and other fine internet sites:
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- From the Nat. Library of Medicine:
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