Bronchoalveolar casting using formalin-fixed canine lungs and a low viscosity silicone rubber

A method for creating tough, flexible, bronchoalveolar casts from formalin-fixed canine lung is described. A lung was washed using simple methods and fixed in 10% neutral-buffered formalin. While still wet with formalin, an intact lobe was injected with silicone sealant, Silastic 734 RTV (Room Temperature Vulcanizing), using a caulk gun. Following digestion with protease and corrosion with potassium hydroxide, a bronchoalveolar cast was recovered giving detail as shown using scanning electron microscopy or conveniently seen by stereo light microscopy. This method should be useful for micro-anatomy studies of normal and diseased lungs.