When bacteria gets in urinary bladder and the ureters from the urethra. If not treated bacteria can spread to kidneys & cause damage to nephrons.
Collection of salt and waste that have joined together to form a crystal. Stones get stuck in tubes leading from the kidneys to the urinary bladder or in the urethra. This is very painful.
Nephrons in kidneys get damaged. When you have this, nephrons don't function properly so you need your blood artificially filtered.