KIDNEY stones are hard crystals that form in the urinary system. They are very common in Malaysia, with an estimated 1 in 10 Malaysians suffering from them.
They are also more common in men, the overweight and in people over the age of 50, although they can occur in anyone.
The main causes of kidney stone formation are dehydration and excess minerals in the urine. Certain metabolic conditions can also cause stones, but this is less common. Unfortunately, the incidence of kidney stones is increasing as our population ages and rates of obesity rise, as well as a richer diet.
People who have formed one kidney stone are also at high risk of forming another, with over 50% having a recurrence over the course of their lifetime.
The majority of kidney stones (about 80 per cent) are made of a substance called calcium oxalate. Others are formed from struvite (magnesium aluminium phosphate) or uric acid.
Each of these has their specific causes and risk factors. For example struvite stones tend to occur in people with chronic urinary infections and uric acid stones form in people with high levels of this substance in their blood, who may also have gout.
Risk factors for the more common calcium oxalate stones are a high salt intake, dehydration and excess calcium in the urine.
Stones that form and remain in the kidney frequently cause no symptoms. Occasionally they cause urinary infections. They typical symptom associated with kidney stones - severe pain in the back and
side – occurs when stones pass into the ureter, which is the thin tube that leads from the kidney to the bladder. This may also be associated with vomiting, bloody urine and fever.
However, not everyone experiences typical symptoms. Some may just have a dull ache in the back or repeated urine infections. Others may have no symptoms at all, and the stones are picked up on scans done for other reasons. If left untreated kidney stones can cause loss of function of the kidney, sepsis, or recurrent pain.
The diagnosis and treatment of kidney stones is carried out by specialists known as urologists. A variety of tests can be used to diagnose kidney stones. Standard x-rays and ultrasound scans are useful for both diagnosis and follow-up, but they do carry some limitations and CT scans are now considered the "gold standard" test to diagnose stones. Urine analysis to look for blood, infections, or crystals is usually carried out as well as blood tests to check kidney function and for infection.
The treatment of kidney stones depends on their size and position, as well as other medical issues faced by the patient. Very small stones in the kidney may not always need treatment but should be monitored. Small stones in the ureter (less than 3mm) have a good chance of passing spontaneously, and sometimes medication is prescribed to help this process.
If there is a larger stone in the ureter, or if it is causing ongoing pain, obstruction or infection then a variety of treatments may be required.
How can stones be prevented in the first place? The single most important method is to avoid dehydration. A good guide to your hydration level is to monitor the colour of your urine – it should be pale yellow or clear, and not dark. How much water to drink to achieve this will depend on your level of physical activity, your exposure to heat and sunlight and also what you eat.
Most people need to drink at least 2 to 3 litres of fluid daily to maintain a healthy urine output, and most of this should be water rather than sweetened or carbonated drinks.
Maintaining a healthy weight is also essential. Excess sodium (salt) in your diet also raises the risk of forming kidney stones, as it increases the level of calcium in your urine. Processed and canned foods tend to have high levels of sodium, as well as instant noodles, soya and fish sauce and fast food. High sodium can also cause high blood pressure, heart disease and stroke.
There is no health benefit in using "exotic" salts as their sodium content is the same as regular salt. An excess of protein or sugar in the diet has also been shown to increase the risk of kidney stones.
A common misconception is that because many kidney stones are made from calcium, that you should avoid foods containing calcium to prevent them. In fact, large-scale studies have shown that this in fact makes you more likely to form kidney stones.
Your diet should include around 1000mg of calcium daily – foods that can help you reach this target are milk, cheese, yoghurt, fish and leafy vegetables. However, calcium supplements can increase the risk of kidney stones and should be avoided if you have suffered from one in the past.
Other supplements, particularly protein and vitamin C, can also increase your risk of kidney stones.
Simple lifestyle changes can be highly effective in preventing kidney stones, and with a disease that can cause such significant pain and misery, prevention is certainly better than cure.
*The writer is a consultant urologist at Pantai Hospital Penang.