Kidney stones result from crystals in the urine aggregating together when the urine becomes highly concentrated. Normally these crystals pass through the urinary tract without problems. Occasionally, if these stones become large enough, they cause obstruction of the kidney drainage system which may result in severe pain, bleeding, infection or kidney failure. The common sites of obstruction from a stone in the upper urinary tract are located at the:
- Junction where the kidney meets the upper ureter
- Midportion of the ureter or
- Lower ureter at its entry into the bladder
Factors that exacerbate stone formation include having persistently concentrated urine, high urinary acidity, and/or lack of inhibitory substances in the urine such as citrate.