Hello! Thank you for the query. Kidneys cyst is a very frequent finding in abdominal ultrasound. Cyst is a kind of empty space filled with clear fluid. It usually does not cause any problems and does not need to be treated. Especially if it is a small cyst (like an inch or so). Her age is not a critical for surgery. Nowadays its not the age important but the general condition. So I suggest your Mother in Law to stop worrying about the cyst. All she needs is an ultrasound once a year and she will be found. Hope this will help. Regards.