Cats are prone to urinary tract infections (=UTIs). You may notice that if the cat strains to pee and visits the litterbox all the time without peeing- or the other way round if a cat pees outside the litterbox.

They may have different causes. Kidney stones are one of them.
If the kidney stones obstruct the urethra completely and they are not treated a cat may die. But you'll notice any problems much earlier- I've never heard of a Pet Talk cat who died.

Don't be worried, your kitten is anyway to young for that