Most people have two kidneys (see illustration below), which "clean" the blood. They filter out water and waste products, making urine.
Kidney stones are formed out of crystals found in the urine. In most cases, the crystals are too tiny to be noticed, and pass harmlessly out of the body. However, they can build up inside the kidney and form much larger stones.
If a stone becomes large enough to block the flow of urine out of the kidney, it can cause pressure, pain and infection. If a stone moves out of the kidney with the flow of urine, it can cause severe pain as it moves through the ureters – the tubes that carry urine from the kidney to the bladder. If a stone gets stuck, an infection can occur. Depending on its size and position, an untreated kidney stone could cause permanent damage to the kidneys.
Depending on where they are located, kidney stones are also known as renal calculi, urinary calculi, urinary tract stone disease, nephrolithiasis, urolithiasis, and ureterolithiasis.
Many kidney stones don't move and are too small to cause symptoms. These are often referred to as "silent" stones.
If a kidney stone causes a blockage, or moves down the ureter, it may cause some of the following symptoms:
- pain or aching in the back on one or both sides,
- spasms of intense pain (anywhere between the bottom of the ribs and the groin),
- bloody, cloudy or smelly urine,
- nausea and vomiting,
- a frequent urge to urinate,
- a burning sensation during urination,
- fever and chills.
These can also be symptoms of a urinary tract infection, or cystitis, which is much more common in young women than kidney stones. Anyone who has one or more of these symptoms should seek medical advice.
Treatment depends on the type and cause of the stone. Most stones can be treated without surgery. Drinking lots of water (two and a half to three litres per day) and staying physically active are often enough to move a stone out of the body.
However, if there is infection, blockage, or a risk of kidney damage, a stone should always be removed. Any infection is treated with antibiotics first. Stones that are too large to pass can be removed in several ways:
Extracorporeal shock wave lithotripsy (ESWL)
This is the most common method and does not involve a surgical operation. Instead, shock waves are used to break the stones into crystals small enough to be passed in the urine. The shock waves do not hurt, although some people feel some discomfort at the time of the procedure and shortly afterwards.
Ureteroscopic stone removal
If a stone is lodged in the ureter, a flexible narrow instrument called a cystoscope can be passed up through the urethra and bladder. The stone is "caught" and removed, or shattered into tiny pieces with a shock wave. This procedure is usually done under a general anaesthetic.
Percutaneous nephrolithotomy (PCNL)
If ESWL doesn't work or a stone is particularly large, it may be surgically removed under general anaesthetic. The surgeon makes a small cut in the back and uses a telescopic instrument called a nephroscope to pull the stone out or break it up with shock waves.
Parathyroid surgery
A small benign tumour in the parathyroid glands (in the neck) can be the cause of the chemical imbalance resulting in kidney stones. If this is the case, the tumour can be surgically removed.
