Initial Experience Using Contrast Magnetic Resonance Imaging in Laminitic Horses: 18 Studies

Abstract

Plain radiographic imaging inadequately identifies soft-tissue pathology and only distinguishes chronic laminitis after the development of notable displacement of the distal phalanx. The window of opportunity for maximum response to treatment occurs before biomechanical failure of the lamellar attachment. Radiographic and magnetic resonance venograms allow vascular assessment of patients affected with acute laminitis. When vascular findings are interpreted with additional magnetic resonance information, the degree of damage to the foot in patients affected with laminitis is understood more thoroughly. This article describes the technique, findings, and outcome in a group of laminitic horses that underwent contrast magnetic resonance imaging.

Introduction

When properly performed, the standing radiographic digital venogram is a reliable diagnostic tool to evaluate the digital vasculature in horses [1], [2], [3], [4]. The venogram has been used to evaluate a variety of pathologies in the equine digit, including laminitis [5], [6], [7]. Serial radiographic venograms (RVs) performed after experimentally induced laminitis show the progression of pathology associated with distal displacement of the distal phalanx as the hoof transitions from normal to chronically laminitic [5], [8]. Characteristic filling deficits of contrast solution on the radiographic digital venogram are similar in appearance to the corrosion casts of chronic laminitic patients, corresponding to areas of venous compression secondary to distal phalanx displacement [9], [10]. In clinical practice, serial standing RVs evaluate effectiveness of therapy and direct treatment [11], [12], [13]. Because the availability of magnetic resonance imaging (MRI) is increasing in horses, it has been shown to be a superior diagnostic modality to evaluate soft-tissue and bone in the foot [14], [15], [16]. However, its use in the live laminitic patient has not been described. This article describes how contrast MRI of the digital venous system was performed and interpreted on a group of laminitic horses, together with a few additional pertinent soft-tissue findings associated with the laminitic horse which have not been previously reported (most of the soft-tissue pathologies delineated by MRI will be detailed in a different publication).