It is common for bladder stones to develop during this procedure due to the fact that urine sits in the bladder for a long time, causing crystals to form that develop into hard lumps.

But while they vary in size and shape, bladder stones do not normally grow more than a few centimetres. Doctors recorded the size as being 12cm (4.7 inches) by 9.5cm (3.7 inches) and the weight as 770 grams. They also found a smaller stone.