Ask Your Veterinarian Presented By Equistro: Venograms Tell The Real Story Behind Laminitis

by | 06.04.2019 | 12:00pm
A normal venogram image

QUESTION: What are venograms and how can they be used in equine diagnostics?

DR. RAUL BRAS: One of the most significant developments not only in the evaluation and treatment of laminitis, but also our understanding of the mechanics of the foot in general, has been the venogram. The venogram is a simple but technique-sensitive procedure that for the first time allows us to visualize the vascular tree of the foot. 1,2,3 The venogram has become an invaluable tool that allows us to visualize the effects of pathology and various treatment concepts, making it one of our most worthwhile tools for diagnosis and treatment strategies.4

It provides the first detectable evidence that confirms laminitis, clearly distinguishing it from other syndromes with similar clinical signs, and it reveals the damaging effects of laminitis earlier in the syndrome than radiographs. Previously, our only means of diagnosing laminitis at the time of onset was history and clinical signs. However, the venogram results are the only thing that distinguishes these symptoms as laminitis, rather than other syndromes.

Dr. Raul Bras

Venograms may also clearly demonstrate extensive vascular damage that can be present in acute cases that exhibit subtle soreness, indicating pain level is not an accurate prognostic or response indicator. Comparative venograms are a more reliable means of assessing damage or actual response to therapy. Far too often cases that are considered clinically stable take a devastating turn for the worse four to six weeks post onset as the vascular supply continues on a downhill spiral despite a seemingly favorable improvement. Vascular reperfusion is a more meaningful representation of the term “clinically stable” than the overall pain response. We no longer look only at the horse's pain relief to define progress, as doing so can be very misleading.

Having this information from the venogram at the time of first clinical signs or shortly thereafter allows us to take advantage of the treatment window to achieve the best response, enhancing our ability to make more timely decisions concerning reversal therapy and also providing a baseline that facilitates monitoring the efficiency of our chosen treatment regimen. This can offer a much more favorable prognosis than if we wait until radiographic evidence confirms that significant displacement has occurred.

An abnormal venogram showing areas where the blood supply has reduced

Venograms require basic radiographic equipment and are easily performed in the standing horse. They are technique-sensitive and require careful attention to timing, technique and positioning relative to load on the digit.5,6 Interpretation requires an in-depth working knowledge of the healthy vascular pattern, as well as the large range of alterations that occur relative to the severity of insult and response to treatment. To avoid unwarranted damage to the laminae while the feet are blocked for the venogram, and a 20° palmar angle device is applied to reduce deep digital flexor tension.

Significant progress has been made in the evaluation and treatment of laminitis. Assessing internal damage with the venogram allow us to better understand the correlation between the vascular pattern and healing response and how the mechanical component greatly influences both. Using sheer mechanics and shifting the load from the anterior half of the foot to the heel proves to be the most reliable means of treating this disease, and doing so in a timely fashion before the destructive cycle has caused irreversible damage to the soft tissue growth centers and the palmar rim, can offer favorable results in a large majority of cases. Prognosis overall is relative to damage at the time of insult, which sets the stage for soft tissue damage followed by mechanical disruption of the equilibrium between the laminae and deep digital flexor tendon.

Time is of the essence, but ideal results may be obtained by quickly re-establishing a healthy vascular supply, which can prevent the mechanical phase from destroying the suspension network.

References:

  1. Redden RF. Clinical and radiographic examination of the equine foot. In: Proceedings of the 49th Annual American Association of Equine Practitioners Convention 2003;320-327.
  2. Rucker A, Redden RF, et al. How to perform the digital venogram. In: Proceedings of the 52nd Annual American Association of Equine Practitioners Convention 2006.
  3. D'Arpe L, Bernardini D and Coppola L. How to do a digital venography in the standing horse. In: Proceedings of the 10th International Congress of World Equine Veterinary Association. Moscow, 2008;529-530.
  4. Redden RF. The use of venograms as a diagnostic tool. In: Proceedings of the Bluegrass Laminitis Symposium. Versailles: International Equine Podiatry Center, 1993;1-6.
  5. Redden RF. A technique for performing digital venography in the standing horse. Equine Vet Educ (2001):128-134.
  6. Rucker A, Redden RF, et al. How to perform the digital venogram. In: Proceedings of the 52nd Annual American Association of Equine Practitioners Convention 2006.

Dr. Raul Bras is a certified journeyman farrier and veterinarian in the podiatry department at Rood and Riddle Equine Hospital. A member of the International Equine Veterinarian Hall of Fame, Bras graduated from Ross University and completed the farrier program at Cornell University. He is a partner at Rood and Riddle.

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