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Proud flesh, also known as granulation tissue, is a type of healing tissue in horses that forms naturally as part of the wound repair process. This tissue aids in wound healing by closing the gap between exposed soft tissue and new layers of skin. [1]
Proud flesh can become problematic in horse if it grows excessively and interferes with normal healing. When too much of this tissue grows, it is referred to as exuberant granulation tissue (EGT). [1]
Lower limbs in horses are prone to developing excessive proud flesh because they have minimal soft tissue coverage and reduced blood supply. Additional factors that contribute to EGT include excessive movement of the healing tissue and contamination (infection) of wounds. [1]
To prevent EGT, it’s essential to promptly attend to any wounds, especially those on the lower limbs. Keeping wounds clean, controlling infection, and minimizing movement in the early stages of the healing process can significantly reduce the risk of EGT formation.
Treatment of proud flesh may involve topical medications, surgical removal, skin grafting, and sometimes bandaging or casting. Consult with your veterinarian regarding the best treatment approach for exuberant granulation tissue to support optimal healing.
Proud Flesh in Horses
Granulation tissue is a natural part of the wound-healing process in horses and other mammals. It can develop in healing wounds on any part of the body. Compared to other animals, wounds on horses develop granulation tissue quite rapidly. [1]
This tissue consists of new blood vessels, fibroblasts, immune cells, and an extracellular matrix, but has no nerve supply. It has an unsightly pebbly or granular appearance. Upon microscopic examination, granulation tissue presents as a disorganized population of cells.
The development of granulation tissue enables exposed soft tissues to connect to new layers of skin. This tissue is beneficial in wound healing as it: [1]
- Helps to prevent infection in the wound
- Helps wounds contract
- Provides a surface for skin cells to move across to fill in the wound
However, granulation tissue is also susceptible to breaking and being reinjured.
Exuberant Granulation Tissue (EGT)
Exuberant granulation tissue (EGT) is excessive granulation tissue that impedes normal wound healing. Some horse wounds develop EGT, which grows until it protrudes from the site of injury, occasionally resembling a tumor.
EGT prevents skin cells from covering wounds (epithelializing) and interferes with hair regrowth. It can be very challenging to treat, can delay wound healing, and may result in the loss of use of the horse.
EGT commonly develops in poorly contracting wounds. [1] Skin wounds that are left open to heal are more likely to develop EGT compared to those closed with sutures.
Wounds on the lower leg of the horse, such as over the cannon bone or pastern area are particularly prone to developing EGT. A lack of oxygen due to reduced blood flow likely plays a role in the development of EGT. [2]
Wound Healing Process
Wound healing typically progresses through four stages: clotting, localized swelling, tissue rebuilding, and tissue remodeling, occurring in this specific sequence.
Granulation tissue is needed to fill in wounds situated over tendons, ligaments, bone, and other important structures. This tissue develops before new skin cells can migrate over top of it to repair wounds.
During the normal healing process, granulation tissue is remodeled as its components are synthesized and degraded. This tissue should stop growing once a wound has filled in, enabling wound contraction and coverage with new healthy skin. [1]
Exuberant granulation tissue develops due to an abnormal healing process. When EGT develops, skin cells cannot migrate over top of the tissue to heal the wound. As a result, the granulation tissue grows until it protrudes above the wound, resulting in the phenomenon known as proud flesh.
Factors such as wound contamination, infection, inflammation, and movement can interfere with the healing process and result in chronic wounds. [1]
Causes of Proud Flesh
The development of proud flesh in horses typically arises from multiple causes and can be linked to any of the following contributing factors: [1]
- Inflammation: Persistent and prolonged inflammation in wounds is the primary factor believed to promote EGT. An ongoing cycle of inflammation commonly due to re-injury or exposure to irritants and poor contraction can cause granulation tissue to continue growing.
- Biological Imbalances: An imbalance between the production and degradation of collagen is associated with the development of EGT. Abnormal programmed cell death (apoptosis) impairs the elimination of unnecessary cells and contributes to the development of EGT.
- Blood Supply: Areas of the body such as the lower limbs have less tissue coverage with a reduced network of blood vessels and limited blood supply. This can hinder proper wound healing and promote EGT.
- Excessive Movement: Frequent movement and pressure on wounds can interfere with healing and promote EGT.
- Contamination and Infection: If a wound becomes contaminated with dirt, debris, or bacteria, it can disrupt the healing process and trigger the development of EGT.
- Poor Wound Management: Inadequate wound care, such as improper cleaning, dressing, or bandaging, can impede healing and contribute to the development of EGT.
- Delayed Treatment: If a wound is not promptly addressed and treated, it is more prone to developing EGT.
Horses vs. Ponies
Research indicates that horses are more susceptible to developing proud flesh compared to ponies. [3][4]
Upon tissue injury in both horses and ponies, white blood cells initiate an inflammatory response. In ponies, this white blood cell response leads to increased wound contraction, a faster transition to the wound repair phase, and more rapid healing than in horses. [1]
In horses, the inflammatory response to tissue injury is not as pronounced as in ponies and can become chronic. This chronic inflammatory response inhibits wound contraction and promotes the formation of EGT. [1][9]
Research indicates that during the initial ten days of wound healing on a limb, the concentration of a cell signaling protein known as transforming growth factor-β (TGF‐β) is lower in horses than in ponies. This protein plays a pivotal role in wound contraction. [1]
Based on this research, it is hypothesized that wound contraction might be less efficient in horses than in ponies due to a diminished concentration of TGF‐β. [1]
Diagnosis
If you suspect your horse has developed exuberant granulation tissue, it is important to consult with your veterinarian to ensure an accurate diagnosis. Your veterinarian can discern whether a wound on your horse’s body is forming normal or exuberant granulation tissue.
Diagnosing proud flesh in horses is generally straightforward, as the appearance of this tissue is quite distinctive. Your veterinarian will diagnose granulation based on: [1]
- Visual Examination: Your veterinarian will visually inspect the wound and the surrounding tissues. They will examine the wound for the distinct features of normal granulation tissue compared to EGT, which manifests as an excessive growth of pinkish or reddish tissue with a rough or bumpy texture.
- Palpation: Your veterinarian may gently touch the wound to assess the texture and extent of granulation tissue growth. They may also evaluate the wound’s firmness and vascularity.
- Measurements: The size and dimensions of wounds and granulation tissue may be measured to monitor any changes over time.
- Differential Diagnosis: Your veterinarian may need to rule out other potential causes of wound healing issues, such as infection, foreign bodies, or abnormal growths (neoplasms). Occasionally, other disease processes such as sarcoids, parasitic infection (habronema), fungal infections, or tumors may appear similar to granulation tissue. [1]
- Medical History: Your veterinarian may ask questions about your horse’s medical history, any recent injuries, and the wound’s progression to gather more information.
- Skin Biopsy: In some cases, a biopsy may be performed if there are concerns about the wound’s healing progress or if your veterinarian suspects an underlying issue that requires further investigation.
Treatment
Prompt treatment and guidance from your veterinarian are crucial for managing exuberant granulation tissue in horses to prevent complications or worsening of the condition.
The preferred treatment approach for wounds exhibiting proud flesh depends on the extent of tissue overgrowth and w