Myth-busting and some simple truths about preventing kidney stones

I see a lot of patients who come to me when they pass a stone or need to have a procedure to have removal of one.  My heart is with them, as they describe the experience as the most severe pain in their life and they wish it will never be repeated in the future.  For that reason, patients are very keen to avoid further episodes of stone passage and want to find out about the stone prevention. This advice is especially important as we also know once a person has developed stones, the likelihood of them having another occurrence is raised to about 50 per cent over 10 years.

There is frequently a lot of confusion around the topic.  My advice that the most important part of change which they need is increased fluid intake.  It has been proven that if a person has urine output of more than 2.5 litres per 24 hours, they are unlikely to form stones.  The type of fluid is not as important, as volume, so it could be pure or flavoured water or diluted juice.  Stone formers are advised to avoid black tea, as it contains high amount of oxalate, a frequent component of stones.  Citrate-containing drinks, such as lemonade, are useful, as they provide citrate, which is a stone-formation inhibitor, but be mindful of intake of calories with soda type drinks.

A person could judge whether they drink enough fluid accurately by measuring the volume of urine produced over 24 hours, as each individual fluid intake would vary, depending on their activity and ambient temperature.  For example, a tall athlete would require fluid input of over 3.5 litres to compensate for sweating during exercise.

If urine dilutes enough, the substances which form stones will not clump together.  It will not dissolve already existing stones but will prevent their growth and appearance of new deposits for stone formation.

The other important change is diet.  Reduction of salt and animal protein will lead in reduction of propensity to form stones, so goodbye bangers and mash and hello salad.

Calcium oxalate is the most common type of stones.  Oxalate is encountered in chocolate, strawberries, grapefruit and spinach, so these foodstuffs are allowed in moderation.  The advice to reduce calcium rich foodstuffs, such as milk, is outdated, as calcium binds oxalate in the bowel and prevents it getting into the body.

Increased vegetable consumption is also helpful, as it alters pH of urine to alkaline and makes stone formation less likely, which is important for the other common type, urate.

In conclusion, stone prevention is a question of altering diet and is entirely in the hands of an individual.