Tissue changes in enlarged sternal bursas of turkeys.

Enlarged sternal bursas evident in turkeys beyond 12 weeks of age were examined grossly and microscopically in 169 turkeys 3 to 26 weeks old. Grossly, the enlarged sternal bursas were sacs of varied size and wall thickness containing fluid in amounts from a fraction of a milliliter up to 70 ml. The fluid was usually the consistency of serum but was sometimes viscid, and in infected bursas it would be purulent. Its color varied from amber to red to dark brown depending on the amounts of and the changes in the blood pigments. The synovial membranes were smooth and glistening and of variable thicknesses. Strands or cords of the synovial membrane of variable thickness and number extended from side to side of the sac. Microscopically, the synovial membrane was focally thickened in the small bursas and generally thickened in the larger bursas. The thickening was the result of an increase in the very cellular fibrous tissue and in the number and size of blood vessels. The lining cells were flat fibrocytes one cell thick in the smaller bursas, and round stratified cells in the larger bursas. In infected bursas, mononuclear and heterophilic infiltration occurred. Hemorrhaging occurred quite often, the result of trauma to the highly vascular synovial membrane.