How to Use Digital Venograms to Evaluate Laminitis
"The venogram is the ticket to fixing all those laminitis cases you've been missing," Amy Rucker, DVM, said at the Bluegrass Laminitis Symposium (held Jan. 25-28 in Louisville, Ky.). Rucker, a practitioner with Midwest Equine in Columbia, Mo., discussed how to use the digital venogram (a radiograph or X ray of the foot taken with contrast media injected into the blood vessels to visualize any blood flow problems) in clinical situations.
She began by listing the phases of laminitis: Developmental, acute and subacute (some mechanical collapse), and chronic. "Each phase has different degrees of damage, and they can bounce between the chronic and acute stages (chronic with flareups)," she said. "When you start thinking about the phases of disease and classifying horses into these groups, it tells you a bit more about what's going on and you can decide what to do a little easier." The results of a venogram help her determine which phase a horse is in, she noted.
She described the phases of laminitis and their venogram characteristics as follows.
Developmental phase--This begins with exposure to causative factors and triggering of laminar separation, and it lasts 24-30 hours. Lameness is not apparent. Venograms taken during this phase should be normal, but if there is leakage of contrast from the vessels or if the papillae (tiny "fingers" of blood vessels pointing down from beneath the bottom of the coffin bone) are beginning to fold, or if they are compressed and not visible, then laminar separation has begun (and the horse has moved on to the acute or chronic phase).
Acute phase--This phase begins when the feet change clinically, digital pulse is increased, and the foot is painful when bearing weight. It is diagnosed using physical examination, radiographs, and venograms. Treatment includes addressing the primary disease, giving anti-inflammatory medication, supporting the foot with proper mechanics, and enforcing absolute stall rest.
With mild blood vessel damage during the acute phase (as seen on the venogram), a proper shoe will support the foot and healing. With moderate damage where the coffin bone has rotated past the circumflex vessels that normally run beneath it, she performs a deep digital flexor tenotomy (cuts the tendon) to reduce the pull of the tendon on the laminae. With severe damage, structural collapse of the foot will follow. Euthanasia or aggressive treatment such as pin casting and wall resection are the only options.
Affected horses might enter the subacute phase if initial treatment minimizes changes within the foot, structural damage doesn't occur, and the horse quickly returns to soundness. Venograms performed during the subacute phase show normal blood flow.
Chronic phase--Unfortunately most horses have changes within the hoof capsule and enter this phase. Some chronic cases can stabilize and are then called "compensated," or serviceably sound. Other chronic cases continue to have severe pain and lameness (uncompensated). Their venograms will vary widely depending on the degree of damage and individual factors.
"Laminitis is a medical emergency, and should be treated as such," Rucker stated. "Waiting to see how the horse does over time (without treatment) only decreases your chances of having a functional horse. The basis of treatment of the laminitic horse relies on correcting the initiating disease process, medically managing the pain of the horse, and altering the mechanics of the hoof to place it in a healing mode.
"For the foot to repair, the laminae and dermis cannot be damaged beyond repair, and the foot must have an adequate blood supply throughout," she went on. "The venogram shows where blood is in the foot; if the foot is unstable, that will affect the blood supply within it. The amount and patterns of displacement of the contrast media suggest where the foot is heavily loaded, where architecture has collapsed, and/or areas of vascular impairment. Patterns are also identified as typical of acute or chronic changes, which helps determine the state of disease.
"Also, serial venograms allow assessment of progress in a case, or lack thereof," she added. "Always trust the venogram before the clinical picture. Clinically they can look really good even with a very bad venogram (and when this occurs, the horse that looks fairly sound will later crash due to the compromise of blood flow in his foot)."
She listed the following five principles of mechanically treating the laminitic horse to improve blood flow and healing:
- Move breakover (the forwardmost point on the bottom of the foot that touches the ground on a hard surface) back. This reduces the lever arm of the toe, which pulls the laminae apart as the heel lifts off the ground.
- Unload the deep digital flexor tendon. Increasing the palmar angle (the angle the wings of the coffin bone make with the ground) will do this.
- Derotate the foot. The palmar surface of the coffin bone should be parallel to the load-bearing solar surface of the foot.
- Load the relatively healthy portion of the foot (the rear part of the foot in most laminitic horses). Provide support for the sole, especially in the heels, bars, and frog. Do not place pressure on the sole beneath the apex of the coffin bone.
- Do not stress the foot--be fast with treatments and keep the palmar angle elevated. Never take an unstable foot out of a therapeutic device/shoe and leave the horse standing flat-footed, and do not walk him.
Case in Point
Rucker described venogram characteristics and case progressions with several cases to illustrate her points. At the end of her discussion, Symposium organizer Ric Redden, DVM, founder of the International Equine Podiatry Center in Versailles, Ky., weighed in with another brief example of how venograms can guide treatment.
"I treated one stallion that had been sound for a few months in Modified Ultimate wedge shoes and had bred a few mares, and we were thinking about putting him back in regular shoes," he recalled. "But I wanted to do one more venogram session to test the system. I took a few views with the Ultimates on, a few with them off, and then another with the Ultimates on. I saw 3-4 mm papillae with the Ultimates on, none with them off, and they came back with the Ultimates back on. That horse still had an unstable foot. If he was ready to come out of those shoes, his papillae would not have crushed when I took the Ultimates off."
Thus, the horse stayed in the Ultimates for awhile longer, possibly staving off a crash from moving to plain shoes before the foot was stable.
If Your Horse Gets Laminitis...
Remember how Rucker said laminitis was an emergency? If you go out to the barn one night and see your horse shifting weight uncomfortably from foot to foot and rocking back on his hind feet to take weight off his sore front feet, it's time to jump into action, she says. Quick action can also help the horse that's at risk for laminitis but isn't yet lame (such as the one you discover in the feed room up to his ears in sweet feed).
"When your horse shows clinical signs of laminitis, damage to the hoof architecture has already occurred," she stated. "How you respond to these signs will help determine the course of the disease." Following are the steps she recommends horse owners perform even before the veterinarian and farrier arrive:
Limit movement of the horse, she emphatically recommends. Ignore old thoughts of walking the horse to "increase circulation;" movement will further damage the unstable architecture of the foot.
If you suspect the horse is at risk for laminitis, but he isn't yet lame (i.e., he got in the feed room or out onto a rich pasture he doesn't normally graze), stand him in an ice water bath up to his knees and hocks. Research shows that doing this before lameness develops might prevent the disease from occurring. After lameness has appeared, this method will not help and might actually compromise the blood flow the foot needs to heal.
Support the sole of the foot with Styrofoam or other soft material until help arrives.
Call your veterinarian and farrier. Success with laminitic horses depends on 100% effort from the owner, farrier, and veterinarian, she said.
Rucker, A. Interpreting Venograms and Artifacts. April 2003, www.TheHorse.com/ViewArticle.aspx?id=4249.
West, C. Understanding the Venogram. March 2003, www.TheHorse.com/ViewArticle.aspx?id=4076.
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.