Anatomic variations of efferent duct from caudal mediastinal lymph node in sheep

Collection of lymph from the efferent duct of the caudal mediastinal node in sheep is accepted as a reliable method for following lung microvascular fluid and protein filtration. There are significant variations in the efferent duct anatomy, which can complicate the cannulation procedure and, therefore, the success of the preparations. We analyzed the major variations in the efferent duct in 75 consecutive sheep. The majority (59%) had a single efferent duct varying in length, course, and origin fom the caudal mediastinal node; 41% had multiple ducts, often with confluences or bifurcations, making successful cannulation more difficult. It is important to recognize the potential variations in the efferent duct to facilitate useful cannulation.