The urine starts to form mineral crystals when the bladder is not empty completely. Because of this, the urine becomes concentrated urine, which in turn crystallizes and forms stones.

Some other causes of bladder stones include:

Infection: Infections caused due to bacteria or other organisms. Urinary Tract Infection (UTI) is the common cause of bladder stones. While urinary infection is common in women, men are more prone to bladder stones.

Enlarged Prostate Gland: An enlarged prostate gland presses against the urethra which interferes with the urination process. This causes the bladder to not be emptied fully and thus results in bladder stones.

Weak Bladder: The weakening of your bladder walls forms pouches. The urine is collected and stored in these pouches. Later, this stored urine forms the bladder stones.

Neurogenic Bladder: Damage to the nerve that carries information between the bladder and nervous system may result in the bladder not getting emptied fully. The damage could be due to spinal injury or any other problem. It breaks communication between the mind and the bladder.

Damaged Urethra: A damaged urethra narrows down due to infection and blocks the flow of urine. The urethra can be damaged due to a disease, or illness. This causes the urine to remain in the bladder.

Kidney Stones: The presence of small kidney stones may result in bladder stones as they travel down the tubes that carry urine from kidneys to the bladder.