Overview
Kidney stones are hard, pebble-like lumps that form when minerals and salts in the urine stick together. They can be as small as a grain of sand or, less often, much larger.
A stone may stay in the kidney or move into the , the tube that carries urine to the bladder. Small stones often pass out in the urine with little trouble. A stone that gets stuck can block the flow of urine and cause severe pain. With treatment, kidney stones rarely cause lasting harm.
Most stones are made of calcium. Others are made of , form after urinary infections (struvite stones), or result from an inherited condition (cystine stones).
Symptoms
Small stones may cause no symptoms. When a stone moves or blocks the , symptoms can include:
- Sharp pain in the back, side, lower tummy or groin, which may come in waves
- Blood in the urine, which may look pink, red or brown
- Pain or burning when passing urine
- A constant urge to pass urine
- Cloudy or foul-smelling urine
- Nausea or vomiting
- Fever and chills
When to see a doctor
See a doctor if there is pain in the side or back that does not settle, blood in the urine, or pain when passing urine.
Causes
Stones form when the urine holds high levels of stone-forming substances, such as calcium, oxalate and . When the urine is concentrated, these can form crystals that slowly grow into stones. Not drinking enough fluids is a common reason.
Risk factors
- Not drinking enough fluids
- A previous kidney stone, or a family history of stones
- Being male
- Obesity
- A diet high in salt or animal protein
- Repeated urinary tract infections
- Conditions such as gout, overactive parathyroid glands and inflammatory bowel disease
- Long-term use of certain medicines, such as some diuretics (water tablets)
Complications
Most stones cause no lasting damage when treated. Possible complications include:
- Urinary tract infection or kidney infection
- Blockage of urine flow from the kidney
- Loss of kidney function if a blockage is left untreated
- Further stones in the future
Prevention
- Drinking enough fluids through the day to keep the urine pale
- Drinking more in hot weather, during exercise or after heavy sweating
- Cutting down on salt
- Eating moderate amounts of animal protein, such as meat, fish and eggs
- Not cutting out calcium-rich foods unless a doctor advises it
People who have had a stone may be given specific diet advice or medicines, depending on the type of stone.
Diagnosis
After asking about symptoms, a doctor may arrange:
- Urine tests for blood, infection and stone-forming minerals
- Blood tests for kidney function, calcium and
- An scan, X-ray or to show the size and position of the stone
- Analysis of a stone that has been passed, to find its type
Treatment
Treatment depends on the size and position of the stone. Small stones often pass on their own, helped by plenty of fluids, pain relief and sometimes a medicine that relaxes the .
Larger stones, or stones causing blockage or infection, may need a procedure:
- Shock wave : shock waves from outside the body break the stone into pieces small enough to pass
- : a thin telescope passed up through the bladder removes the stone or breaks it up with a laser
- Percutaneous nephrolithotomy: a keyhole operation through the back, used for large stones
A thin tube called a is sometimes left in the ureter for a short time to keep urine flowing.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Drinking beer flushes the stone out.”What is true?
Fact
No drink dissolves a stone or pushes it out. Drinking enough liquid, mainly water, is the most useful thing for preventing stones, and a stone that is causing severe pain or blocking the flow of urine needs medical care.
Myth“If you have stones you must give up milk, curd, paneer and everything with calcium.”What is true?
Fact
Calcium in food is not the cause of calcium stones, and cutting it out can weaken the bones. Unless a doctor advises otherwise, keep getting enough calcium from food. It is salt, and sometimes large amounts of animal protein, that more often need to come down.
Myth“The stone has passed, so that is the end of it.”What is true?
Fact
Stones often come back, and many people who have had one have another within a few years. Keeping up the fluids, cutting down on salt and following the advice given for that type of stone all lower the chance of a repeat.
Myth“Every kidney stone needs an operation.”What is true?
Fact
Most stones are small enough to pass in the urine, helped by plenty of fluids and pain relief. A procedure is needed for larger stones, or when a stone is blocking the kidney or causing an infection.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
Will a kidney stone pass on its own?
Many small stones do. Larger stones are less likely to pass and may need a procedure. A doctor can advise based on the size and position of the stone seen on a scan.
How much water should I drink to prevent stones?
There is no single amount that suits everyone. A practical guide is to drink enough that the urine stays pale, and more in hot weather. People with heart or kidney disease should ask their doctor how much fluid is safe for them.
Should I stop eating calcium-rich foods such as milk and curd?
Usually not. Calcium from food does not raise the risk of the most common type of stone. Diet advice depends on the type of stone, so it is best guided by a doctor or dietitian.
