Kidney stone crystals, coloured scanning electron micrograph (SEM). Kidney stones are usually formed by the precipitation of the mineral salt calcium oxalate from the urine. The resulting hard, round stones (calculi) may cause severe pain, especially as they pass down the urinary tract. Large stones may need to be surgically removed or broken down using ultrasound therapy.....

Kidney stone. Coloured abdominal X-ray showing a kidney stone (small pale rounded area just right of the vertebral column at upper right) in a male patients left ureter. The stone (small blue dot) is just to the right of the backbone (blocks down centre). Each of the two kidneys (not seen) has a ureter that channels urine to the bladder (not seen). Kidney stones are deposits of calcium salts that ...