Seeing all four parathyroid glands is the best way to ensure that you are removing all of the diseased glands and leaving in normal ones. However, there can be a risk: when you look at all four parathyroid glands (or even attempt to look at all four parathyroid glands), you are creating scar tissue, which could then make future operations more difficult. There is even a risk that during the dissection required to find the gland, you will inadvertently injure the gland. In experienced hands, this should almost never occur, though. The main risk, then, is that you are creating scar tissue that could make the next operation more difficult.   If you know that you can find all four glands safely in the majority of cases, then I believe the benefits of doing so outweigh that small risk that you might need another operation down the road. Remember that if all four parathyroid glands are seen and the ones remaining are normal, then the chance that you would need another parathyroid operation are extremely low. Looking at all four glands during one operation is the best way to ensure that only one operation will be needed.   If your surgeon is inexperienced, then it is safer for him or her to only go after one parathyroid gland and leave the remaining glands alone, because there is significant risk to the glands in inexperienced hands. If your surgeon can safely locate and examine the parathyroids without injuring them, then that is a better way to ensure a cure.