Dear Dr. G,

I understand the month of January is dedicated to the prevention of urological conditions, and my resolution this year is to stop the agony that is kidney stones.

As a 40-year-old man who has been unlucky enough to endure the agony of kidney stones over the last five years, including an incident where I had to be rushed to the hospital during the movement control order (MCO) for an operation, can you please tell me what causes kidney stones in men?

Can you tell me how many types of stones are there and if they can be genetic in origin?

I also ask this as I was told at a recent check-up that another stone has formed and I have been advised to undergo shockwave treatment as the stone is quite small and not causing havoc for now.

With this, I ask what my New Year dietary resolutions should be so that I will never face the agony of kidney stones again in my life?

I look forward to your dietary guidance and wish you a healthy New Year!


Stony Steven

Kidney stones or nephrolithiasis are usually caused by crystallisation in one or both kidneys and move in the urinary tract following the urine stream.

Generally, a small stone that measures less than 5mm would pass with minimal symptoms, however concretions larger than 5mm result in typical renal colic. This in turn causes a blockage in the ureter as it has a diameter of 5mm.

A renal stone attack is typically described as severe, sharp and sudden pain felt in the back, radiating to the front and the groin. The pain is usually associated with nausea and vomiting, and not relieved by any manoeuvre or bodily positions.

Kidney stones have been known to mankind since 600BC, as descriptions of the surgery have been depicted in historical records for more than two thousand years. On average, between 1% and 19% of people are affected by kidney stones at some point of their lives.

Kidney stones are believed to be more common in the western world since the 1970’s. This is believed to be associated with dietary habits and lifestyle choices and tend to affect men more than women. Data has revealed that kidney stones can affect up to 19% of men and 9% of women in developed countries such as the United States.

As for the formation, both genetic and environmental factors have a part to play, however the latter is generally more common.

Kidney stones are generally made up of calcium oxalate, uric acid and cystine; a cystine stone is caused by a genetic defect resulting in the abnormal transport of cystine in the body. Such kidney stones affect individuals from childhood and are generally rare.

Having said that, a calcium oxalate stone is the most prevalent as they are 85% of all kidney stones found, while uric acid and cystine stones are only responsible for 14% and 1% of all urolithiasis respectively.

Risk factors for kidney stones include obesity, dehydration and high urinary calcium, oxalate or uric acid. As such keeping one’s urine dilute is by far the most effective way to prevent all forms of kidney stones. A minimal daily fluid intake of 2.5 litres is advisable as a high fluid intake can reduce the risk of urine supersaturation and therefore the likelihood of stones recurring as it increases the transition time of crystals in the urinary tract.

Apart from dehydration, a high salt intake and heavy consumption of animal protein and shellfish are also associated with recurrent kidney stones. High sodium levels in the body can promote the increase in urinary calcium excretion causing hypercalciuria, while animal protein and seafood can increase urinary and blood uric acid levels. High urinary uric acid is not just the fundamental cause of uric acid stones, it also promotes the formation of calcium and cystine in high-risk individuals.

When it comes to oxalates, foods that are high in it include nuts, chocolate, spinach, rhubarb and tea; all of these are well-recognised causes of kidney stones.

Basically, calcium binds with oxalates in the gastrointestinal tract, and the subsequent excretion in the urine can increase the risk of stone formation significantly.

However, it is slightly more complicated when it comes to dietary calcium as a low calcium intake can increase the levels of oxalate that are absorbed. On the other hand, an excessively high calcium intake can also result in hypercalciuria and the formation of other calcium stones, namely calcium phosphate.

Ultimately, when recurrent “stone formers” put Dr G on the spot for dietary New Year’s advice for stone prevention, the best way would be to always stay hydrated and be mindful of the food you put in your mouth.

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