Can kidney stone kill a person ? and can an four year old get kidney stone and gallbladder stones ?

If: It is large and is associated with a blood stream infection. It is unusual for a 4 year old to have stones unless there is an associated metabolic disease. All the best and get some advice from Peds endocrinology.

Yes to all: This sounds like a very serious situation and this child needs to be under the care of a competent pediatric urologist to find the cause of the kidney stone. Gallstones can be lethal as well; in a child, the workup should include a check for ongoing hemolysis, even low-level.