Bladder stones are hard crystals that form when urine sits too long or becomes too concentrated. They act like gravel in a fish tank, scraping the bladder wall every time it moves.

The star symptom is sudden pain at the end of urination. A deep cramp hits when the bladder squeezes the stone against the wall, and it can shoot to the tip of the penis or the lower back.

Urgency and frequency climb. You dash every hour, yet only a small, stop-start amount comes out.

Blood appears. The urine may look light pink, or you see a few red streaks on the tissue after wiping.

Clear or cloudy mucus threads show up. The bladder lining produces extra slime to protect itself from the rough edges.

Interruption sign is classic. The stream stops dead, then restarts after you change position or stand up.

Late signs include a swollen lower belly or fever if the stone blocks the urethra—an alarm that the bladder can’t empty.