Gravel in Horses
Gravel in Horses is the layman’s term for what supposedly is the migration of a piece of gravel from the white line proximally to the coronary band, where it is discharged as an abscess. What actually occurs is an opening in the white line at the sole/wall junction that permits infection to invade the laminae, resulting in the development of a submural abscess. The abscess follows the path of least resistance, and eventually breaks and drains at the coronary band.
Gravel is nothing but the asscending Infection of the White Line in horses.
Etiology
- A wound or crack in the white line
- A separation in the white line (“seedy toe”)
- A subsolar abscess adjacent to the white line may predispose the horse to development of gravel.
- Horses with white line disease and/ or chronic laminitis are usually at greater risk.
- Trauma and penetrating injuries to the sole/hoof wall junction may also contribute to the disease.
Clinical Signs
Moderate to severe lameness appears 1 or 2 days before drainage at the coronary band occurs in Gravel in Horses.
Signs of lameness may also vary depending on the severity and location of the infection.
Hoof tester examination is often helpful to determine the approximate location of the ascending infection before it breaks out at the coronary band.
Careful examination of the white line and sole in the painful region should be performed.
The hoof and sole should be trimmed lightly, and exploration of any black areas (black spots) with a flexible metal probe may reveal the site where the laminae were penetrated. If the probe enters the laminae and exudate is observed this is likely the site of the original defect.
Removal of sole and wall at suspicious sites can be performed to help identify the tract but should be kept to a minimum.
Diagnosis
Diagnostic anesthesia may be helpful in some cases to confirm the location of the lameness to the foot.
A definitive diagnosis often is not made until the abscess breaks out at the coronary band.
Purulent drainage at the coronary band confirms the diagnosis, but if the drainage occurs on the lateral or medial aspects of the coronary band it should be distinguished from necrosis of the collateral cartilages of the distal phalanx.
The tract associated with an ascending infection of the white line is superficial and usually breaks out just proximal to the coronary band. In contrast, draining tracts associated with necrosis of the collateral cartilages erupt from deep within the cartilage, are often multiple, and are usually located 1 to 2 cm proximal to the coronary band.
Fistulograms can be helpful to determine whether the tract is deep or superficial
Treatment
If an ascending infection of the white line is suspected but cannot be confirmed (no drainage at the coronary band), soaking or poulticing the foot may draw the infection to the surface.
When the abscess comes to a “head” just proximal to the coronary band, drainage can be established by lancing the abscess.
If a draining tract is present at the time of presentation, flushing the tract with antiseptics to promote drainage and local wound care is usually all that is needed.
Soaking the foot and irrigating the draining tract usually resolves the infection.
Bandaging the foot or using a protective boot to prevent contamination of the tract openings can be beneficial.
If the drainage persists for more than 7 to 10 days, further diagnostics should be considered to rule out the possibility of a foreign body, keratoma, or infection of deeper structures
Chronic cases with a long history of drainage at the coronary band may cause considerable undermining of the hoof wall.
It may be beneficial in these cases to create a circular hole in the hoof wall midway between the solar surface and the coronary band. This permits better access to more thoroughly debride the tract of necrotic and infected tissue and provides better drainage
Systemic and local antibiotics may be required if the infection involves the regional soft tissues of the pastern or under the hoof wall.
Prognosis
The prognosis is generally favorable if the condition is diagnosed early and adequate drainage and wound care are provided.
The prognosis is guarded if the condition becomes chronic and extensive hoof wall undermining has occurred. However, the majority of these horses also return to complete soundness if treated appropriately