What are the causes and risks of kidney stones?
Individual susceptibility is an important factor to consider in the development of kidney stones. There a number of factors, including dietary, environmental, situational and genetic factors as well as diseases, that may precipitate the formation of kidney stones. The reason why it occurs in some people and not in others facing the same factors in unknown.
However, a number of risk factors for kidney stone development is known.
Low Fluid Intake
Drinking less water or other fluids will decrease urine output. It will also concentrate urine. This will reduce the flushing out of waste products in the urine and allow solutes to precipitate. Drinking caffeinated drinks and alcohol can contribute further towards the development of kidney stones as it dehydrates the body by increasing urine output.
Seasonal episodes of kidney stones may be related to summer or heat waves as the body lose fluid through perspiration (sweating) and urine output decreases. Vitamin D production due to sunlight exposure also increases in summer and this may be a contributing factor in seasonal episodes, especially in a person who is accustomed to living in an area with limited sun exposure.
Low urine output
Urinating less frequently and low urine volumes are another predisposing factor for the development of kidney stones. Since kidney stones continue to grow further in the other structures of the urinary system, holding back urination on a ‘full bladder’ can increase the size of stones.
Foods, Supplements and Beverages
Foods rich in oxalate, like spinach and rhubarb, and high protein foods may contribute towards the development of oxalate stones and uric acid stones. There are a number of other foods to avoid for the prevention of kidney stones. Caffeinated drinks, like tea, coffee and certain soft drinks, and alcohol can dehydrate the body thereby increasing the risk of developing kidney stones. High doses of vitamin C and even moderate doses of vitamin D supplements increase the risk of kidney stones – vitamin C increases oxalate secretion while vitamin D increases calcium absorption and excretion.
Certain drugs may increase the risk of kidney stone development. These include drugs like :
- Diuretics (some diuretics may help reduce recurrent stones)
If there is a family history of kidney stones, a person may be up to three times more likely to develop stones in the course of their life. Some conditions which may be linked to genetic factors include :
While there may be a genetic susceptibility, dietary habits among family members may be similar which could further contribute to the development of kidney stones.
A person prone to repeated urinary tract infections (UTI’s) may be at risk of developing struvite stones. Bacteria in the urine may alter the pH level (acid-base balance) of urine. This can trigger the formation of struvite stones.
Intestinal, Bowel Disorders
Certain diseases of the bowels, including inflammatory bowel disease and disorders that affect the small intestine, particularly the ileum, may increase oxalate absorption and excretion. Surgical removal of the ileum (resection) may also contribute to this.
Any abnormalities of the urinary tract may affect the flow of urine, resulting in pooling or backing up of fluid. This can lead to hydronephrosis which is the accumulation of urine within the kidney. Disruptions in the flow of urine may at times be due to therapeutic measures like a catheter or stent. Some of these abnormalities may be congenital (present at birth) or acquired as a result of other diseases.
A number of metabolic diseases may affect the chemical composition of urine thereby increasing the risk of kidney stone formation. These diseases may cause the following changes in the urine :
- High calcium levels in the urine – hypercalciuria.
- High uric acid levels in the urine – hyperuricosuria.
- High oxalate levels in the urine – hyperoxaluria.
- Low citrate levels in the urine – hypocitraturia.
- High sodium levels – hypernatriuria.
This is the medical term to refer to unknown causes and risks which may predispose a person to the formation of kidney stones.