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Bladder stones are hard pieces of mineral that form in the bladder. The stones may form because of a urinary tract infection or enlarged prostate. Bladder stones happen when urine is concentrated and minerals crystallize and clump together.

Bladder stones may block the tube that carries urine from the bladder to the outside of the body (urethra). The blocked tube may cause trouble urinating, painful urination, or complete inability to urinate.