KIDNEY STONESE
Kidney stones are stones that form in the kidney or the bladder; they are known by doctors as 'urinary calculi'. Kidney stones can vary in size from tiny microscopic fragments to huge stones that fill up much of the kidney. It is a relatively common condition and may affect up to one per cent of adults in Western countries. Men are affected about four times more frequently than women.
Causes of Kidney Stones
The kidneys filter blood and the fluid produced is concentrated and drains out of the kidney as urine into the bladder. Urine contains various substances called ‘salts’ (eg calcium salts), which can potentially form stones if they become too concentrated. Urine also contains substances that inhibit the formation of stones. Therefore, stones can form if the urine becomes too high in salts or if there are not enough inhibitors. Stone formation occurs for many different reasons. Most kidney stones are made of calcium. The most common cause of calcium stones is a condition called 'hypercalciuria', in which large amounts of calcium are excreted into the urine.
Two common known causes of hypercalciuria are:
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kidneys that 'leak' excess calcium into the urine
- absorption of too much calcium from food, which is excreted into the urine.
Sometimes calcium is excreted into the urine because the blood level of calcium is too high. This can be caused by:
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vitamin D overdose,
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overactive thyroid gland,
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overactive parathyroid gland,
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certain kidney diseases,
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cancer,
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a condition called sarcoidosis.
A substance called oxalate, which is present in foods such as rhubarb, spinach and nuts, can also increase the formation of calcium stones. People whose kidneys excrete excess acids (uric acids) into their urine can develop stones made from these substances. Some stones form only in urine that is infected.
Common Symptoms and Complications of Kidney Stones
Small stones may not cause any symptoms at all. Larger stones that become lodged in the tubes that drain from the kidneys into the bladder – the ureters – can cause what is known as 'renal colic'. This is intense pain in the side of the lower back that spreads across the abdomen. It comes and goes and may be accompanied by nausea and vomiting. The affected person may also have chills and a fever, and usually blood is present in the urine. As the stone passes down the ureter towards the bladder, the need to urinate frequently often occurs.
The two major complications of kidney stones happen when a stone completely blocks the flow of urine out of the kidney. The urine trapped above the blockage can become infected and, as the back pressure of urine builds up, the kidney can become swollen and damaged.
If you have a kidney stone, the diagnosis is usually easily made by the doctor based on your symptoms and physical examination. A simple X-ray of your abdomen can confirm the diagnosis because calcium in the stone shows up white on the X-ray. Another test called an intravenous pyelogram (IVP, or IVU) involves the injection of special dye that is excreted by the kidneys into the urine. This dye shows up on an X-ray and can reveal stones that do not contain calcium. An IVP can also show the doctor if the stone is blocking a ureter and causing a build- up of urine.
Your urine is tested for blood and any signs of infection. Other tests may involve collecting urine over a 24-hour period to measure the amount of calcium, oxalate, uric acid and cystine.
Treatment for Kidney Stones
Small stones that produce no symptoms pass out unnoticed in the urine. If a stone causes symptoms, usually you will be admitted to hospital so that strong painkillers can be given. Drinking plenty of fluids and moving around as much as possible often helps the stone to pass out on its own. All the urine you pass is collected and sieved in the hope of catching the stone for analysis. If the stone does not pass and causes complications, it can be removed surgically through a small incision. Infected stones are almost always removed with surgery.
Stones may also be removed from the lower part of the ureter using a flexible tube with a snare on its end (a cystoscope), which is passed up the urethra, through the bladder and into the ureter. Some stones can also be treated using a relatively new therapy called 'extracorporeal shock wave lithotripsy' (ESWL). Ultrasound waves are directed at the stone from a machine outside the body and the stone is shattered into small pieces. You then drink plenty of fluids and the fragments are flushed out in the urine. This treatment is often highly effective and involves no surgery. The procedure is painless and you may be given some sedation before it.
Prevention
Once the stone has passed, steps must be taken to prevent another stone forming. This depends on the reason the stone formed in the first place. Excess calcium in the urine can be controlled by:
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drinking plenty of fluids,
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drugs called 'thiazide diuretics',
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a low calcium diet,
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cellulose phosphate, which reduces the absorption of calcium from food,
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avoiding foods that contain oxalate, such as rhubarb, spinach, nuts, tea, and coffee,
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potassium citrate can help prevent the formation of calcium stones.
Calcium stones caused by the other conditions described are prevented by treating the underlying condition. Uric acid stones are treated using a drug called allopurinol. If you are prone to urinary tract infections, you may be advised to take antibiotics regularly.
Outcome of Having Kidney Stones
Although the pain of renal colic may be excruciating, it can be well controlled with pain killers. Permanent damage to the kidneys caused by stones is very rare, and only occurs with severe infection or prolonged blockage. Unfortunately, kidney stones recur in about 60% of people within seven years of their first episode. Recent medical advances in the treatment and prevention of kidney stones have, however, made a considerable difference to the lives of people with this condition.