There are several factors which influence the ability to pass a stone. These include the size of the person, prior stone passage, prostate enlargement, pregnancy, and the size of the stone. A 4 妹妹 stone has an 80% chance of passage while a 5 妹妹 stone has a 20% chance. Stones larger than 9 妹妹-10 妹妹 rarely pass without specific treatment.