2. Damaged Nerves
When your nerves are functioning properly, the Mayo Clinic says they will “carry messages from your brain to your bladder muscles, directing your bladder muscles to tighten or release.” If these nerves become damaged, however—from a stroke or spinal injury, for example—the bladder may not completely empty when urinating.
This is referred to as neurogenic bladder; a condition that oftentimes requires people to have a catheter inserted into the bladder to help drain it. But even the catheter frequently leaves a small amount of urine behind, which the NHS says “can lead to the formation of bladder stones.” The source adds that this occurs in approximately “one in 10 people with a neurogenic bladder.”