Kidney Stone Advice

What are the types of kidney stones?

Calcium oxalate stones are the most common. They tend to form when the urine is acidic, meaning it has a low pH. Some of the oxalate in urine is produced by the body. Calcium and oxalate in the diet play a part but are not the only factors that affect the formation of calcium oxalate stones. Dietary oxalate is an organic molecule found in many vegetables, fruits, and nuts. Calcium from bone may also play a role in kidney stone formation.

Calcium phosphate stones are less common. Calcium phosphate stones tend to form when the urine is alkaline, meaning it has a high pH.

Uric acid stones are more likely to form when the urine is persistently acidic, which may result from a diet rich in animal proteins and purines—substances found naturally in all food but especially in organ meats, fish, and shellfish.

Struvite stones result from infections in the kidney. Preventing struvite stones depends on staying infection free. Diet has not been shown to affect struvite stone formation.
Cystine stones result from a rare genetic disorder that causes cystine—an amino acid, one of the building blocks of protein—to leak through the kidneys and into the urine to form crystals.

How much fluid should a person drink to prevent stone formation?

The amount of fluid a person needs to drink depends on the weather and the person’s activity level. People who have had a kidney stone should drink enough water and other fluids to produce at least 2 quarts of urine a day. Some doctors have their patients collect urine for 24 hours so the volume can be measured. The doctor can then advise the patient about increasing fluid intake, if necessary. People who work or exercise in hot weather need more fluid to replace the fluid they lose through sweat. Drinking enough water helps keep urine diluted and flushes away materials that might form stones and is the most important thing a person can do to prevent kidney stones.
A person at risk for cystine stones should drink enough water each day to dilute the concentration of cystine that escapes into the urine, which may be difficult. More than a gallon of water may be needed every 24 hours.

What fluids protect against kidney stone formation?

Water is an inexpensive and calorie-free protection against kidney stones.
Some studies suggest citrus drinks like lemonade and orange juice protect against stones because they contain citrate, which stops crystals from growing into stones. But no large-scale trials have been conducted to confirm these findings. While citrus drinks may be helpful in preventing calcium oxalate stones and uric acid stones, they might be harmful for people who form calcium phosphate stones.

Coffee and tea can add to a person’s total fluid intake and have been shown to reduce the risk of stone formation, but they do contain oxalate. Moderate intake of beer and wine may also protect against stone formation.

What fluids should be avoided?

Grapefruit juice and dark colas have been found to increase the risk of stone formation and should be avoided by people who are prone to calcium oxalate stone formation. Although cranberry juice is often promoted as useful for preventing urinary tract infections, it contains oxalate and may be harmful to stone formers.

Citation from American Family Physician