Where Do Kidney Stones Form?

Stones may form in most portions of the urinary tract, including the kidneys, ureters, and bladder.

• Most stones are formed in the kidneys and are referred to as upper urinary tract stones

• Other stones can form in the ureters or bladder and are called lower urinary tract stones

Upper Urinary Tract Stones

Upper urinary tract stones are formed in the parts of the kidneys that play a role in forming or draining urine. Stone formation can occur in:

• The renal tubules, which are the chemical factories that manufacture urine

• The calyces, which are the chambers that drain urine from the collecting ducts at the ends of the renal tubules

• The pelvis of the kidney, the large basin into which the urine collects prior to its journey through the ureters to the bladder

Upper urinary tract stones are most commonly found among people in the United States and in other technologically developed countries.

Lower Urinary Tract Stones

These stones are formed in the ureters or bladder. The stone may have either:

• Originated in the kidneys and traveled to the lower urinary tract before continuing to grow

• Formed directly in the ureter or bladder as a result of crystal formation in the urine

Lower urinary tract stones are most common among people in developing countries.