Imaging diagnosis--nasal septal and laryngeal cyst-like malformationsin a Thoroughbred weanling colt diagnosed using ultrasonography and magnetic resonance imaging.

A foal was examined for abnormal upper airway noise. Endoscopically, there were narrowed nasal passages and an extralumenal mass of the cranial trachea. Using ultrasonography and magnetic resonance (MR) imaging of the larynx and cranial cervical trachea, irregular margins of the laryngeal cartilages and first tracheal ring containing areas consistent with fluid were identified. In MR images, a widened nasal septum was seen that contained material consistent with fluid. Postmortem examination confirmed the diagnosis of nasal septal, laryngeal, and cranial cervical tracheal cyst-like lesions. This is a unique congenital condition, in which premortem imaging was instrumental in defining the abnormalities.