Among domestic animals, cystic ovary disease (COD) is most common in cattle, particularly the dairy breeds, but it occurs sporadically in dogs (see Follicular Cysts in Small Animals), cats, pigs, and perhaps mares.
Three ovarian structures in cattle may include the term "cyst": follicular cysts, luteal cysts, and cystic corpus luteum (CL). However, in contrast to the other two, the structure sometimes described as a cystic CL (a CL with a cavity or "lacunae") actually arises after normal ovulation. CL with a lacunae are a normal stage or variation of CL development and are found in normally cycling and pregnant cows without concurrent abnormal reproductive performance. The lacunae can be compared with the homogeneous, liver-like consistency of the base of a typical CL.
The CL may have an ovulation crown or papilla at its apex; however, 10%–20% of functional, normal CL fail to develop this feature.
The two pathologic forms of bovine cystic ovary disease, follicular cysts and luteal cysts, are etiologically and pathophysiologically related but differ clinically. Both are characterized by the presence of a fluid-filled structure >25 mm diameter, persisting for >7 days and associated with abnormal reproductive performance.