Hoof abscesses are an isolated collection of bacteria that accumulate between the hard hoof wall and the soft, sensitive laminar tissue of the foot. They can occur at any time for a variety of reasons. Most commonly the abscess results from weakening of the connection of the hoof wall to the underlying lamina allowing bacteria to track up the white line. This is unfortunately more common in our area due to fluctuation between wet and dry weather which causes increased water absorption in the foot and the resulting expansion and contraction of the hoof wall during weather changes. Occasionally a close nail will carry bacteria with it as it is driven into a closed space within the hoof which allows the perfect breeding ground for abscess-forming bacteria. Sterile (no bacterial cause) abscesses will sometimes form at the site of an old bruise or increased pressure point on the sole of the foot. Pressure can occur when dirt or stones pack under shoe pads or in sensitive footed horses with pours. Poor trimming and shoeing can result in abscessation to bacteria being trapped in overgrown areas and pressure from overgrown bars. Older horses with Cushing's disease are also prone to developing extensive sub-solar abscesses which can be difficult to manage in horses that may already be suffering from concurrent laminitis.

Abscesses can be extremely painful and often horses show a reluctance to place their foot on the ground or walk. Uncommonly a fever may be present and the leg may swell. Increased heat is readily palpable in the affected foot and digital pulses are dramatically increased and bounding.

With appropriate management resolution of most abscess can be achieved through aggressive medical management bringing rapid relief to a very painful horse. Ideally the abscess can be located and opened immediately with a hoof knife either by the veterinarian or the farrier. In some cases the abscess either cannot be located or the hoof is too hard to achieve adequate drainage. In these instances we utilize aggressive soaking in a warm Epsom salt and betadine solution. This is followed by poulticing and wrapping the foot with a drawing agent such as ichthammol or clay poultice. Leg sweat solutions can also be used to increase heat in the soft tissues aiding in softening the skin and hoof wall. Heat and drawing agents encourage the bacteria to multiply and the abscess to fester its way down the path of least resistance; this is typically out the sole or white line of the bottom of the foot. A small number of horses experience what is referred to as a "gravel." This is when the abscess tracks UP the white line instead of down and ruptures out the coronary band. These typically take longer to resolve and can sometimes be the source of a long term lameness. 

While abscesses are most frequently the result of bacterial accumulation, we generally try to avoid giving antibiotics before the abscess has ruptured or been drained. It is beneficial for the bacteria to multiply and the abscess to grow in order for it to treated more quickly. An abscess by nature is a small pocket of bacteria and for this reason we typically do not have to worry about systemic involvement. In rare cases of long-standing abscess or severely immunosuppressed horses there can be bacterial translocation resulting in systemic involvement which typically presents as cellulitis. Antibiotics may or may not be instituted after drainage has been obtained. Anti-inflammatory medications such as bute or banamine are used to alleviate some pain although compete relief is realistically not possible prior to drainage.

In some horses abscesses can become a chronic problem. In these horses we have to consider other predisposing factors, such as laminitis, Cushing's disease, penetrating wounds, foreign bodies lodged in the hoof wall and hoof wall tumors (keratoma). Further diagnostic imaging including compete radiographic evaluation, peripheral nerve blocks, and metabolic blood testing may be required to determine the underlying cause and an appropriate course of treatment.