 In a recent study spanning 8 years, renal cysts were documented by ultrasound in 7 of 187 healthy Maine Coons enrolled in a pre-breeding screening programme.The cysts were mostly single and unilateral (6/7, 85.7%) small (mean 3.6 mm in diameter) and located at corticomedullary junction (4/6, 66.7%), thus different in size, number, and location from those observed in Persian-related breeds.In the same study, not only did all six Maine Coon cats with renal cysts test negative for the PKD1 mutation, proving the disease in these cats to be unrelated to the PKD observed in Persians and related breeds, but gene sequencing of these cats failed to demonstrate any common genetic sequences.