Renal calculi are solid masses made of crystals. Kidney stones originate in the kidneys, but can be found at any point in the urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra.
The stones form in the urine collecting area of the kidney and may range in size from tiny to staghorn stones the size of the renal pelvis itself. The pain is usually of sudden onset, very severe and colicky, not improved by changes in position, radiating from the back, down the flank, and into the groin. Nausea and vomiting are common.