Anyone who has passed a kidney stone is unlikely to forget it. The pain can be sudden and severe. Kidney stones are common, and once you have had one, the chance of another is high. The encouraging part is that most small stones pass on their own, and a few everyday habits greatly reduce the risk of new ones.
What is a kidney stone?
A kidney stone is a hard deposit that forms when certain substances in urine, such as calcium, oxalate and uric acid, become concentrated enough to form crystals. The crystals stick together and grow. A stone can stay in the kidney without symptoms or move into the ureter, the narrow tube that carries urine to the bladder, where it can cause pain and blockage.
Types of kidney stones
- Calcium oxalate stones: the most common type
- Calcium phosphate stones
- Uric acid stones: more likely with gout, a high-protein diet, diabetes or obesity
- Struvite stones: linked to certain urinary tract infections; they can grow large quickly
- Cystine stones: rare and caused by an inherited condition
Knowing the stone type helps your clinician tailor prevention, so it is worth saving any stone that passes for analysis.
Symptoms
Small stones in the kidney may cause no symptoms. When a stone moves, symptoms can include:
- Sharp, cramping pain in the side or back, below the ribs
- Pain that spreads to the lower abdomen or groin
- Pain that comes in waves and changes in intensity
- Pain or burning when urinating
- Pink, red or brown urine
- Cloudy or foul-smelling urine
- Needing to urinate often or urgently
- Nausea and vomiting
Get urgent medical care if you have
- Pain so severe you cannot sit still or find a comfortable position
- Pain with fever and chills
- Pain with nausea and vomiting that prevents you from keeping fluids down
- Difficulty passing urine
- Blood in your urine with severe pain
Fever with a blocked kidney can signal a serious infection that needs emergency treatment.
Who is at risk
- Not drinking enough fluids, or losing fluids through heavy sweating
- A previous kidney stone or a family history of stones
- Diets high in sodium, animal protein or sugar
- Obesity
- Digestive conditions or surgery that affect absorption, such as inflammatory bowel disease or gastric bypass
- Medical conditions such as gout, diabetes, hyperparathyroidism and some kidney disorders
- Certain medicines and supplements
How kidney stones are diagnosed
Your clinician may use:
- Imaging: a CT scan is very accurate; ultrasound avoids radiation and is often used in pregnancy and for repeat checks.
- Urine tests to look for blood, infection and crystals.
- Blood tests for kidney function, calcium and uric acid.
- Stone analysis of a stone that has passed or been removed.
- 24-hour urine collection for people with repeat stones, to find the chemical causes.
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Treatment
Small stones
Stones under about 5 mm often pass on their own within a few weeks. To help:
- Drink enough water to keep urine pale.
- Take pain relief as advised. Anti-inflammatory medicines are often used, if they are safe for you.
- Your clinician may prescribe a medicine such as tamsulosin, which relaxes the ureter and can help some larger stones pass more easily.
- Strain your urine to catch the stone for testing.
Larger stones or stones that do not pass
If a stone is too large, causes ongoing pain, blocks urine flow or comes with infection, procedures may be needed:
- Shock wave lithotripsy (SWL): sound waves from outside the body break the stone into small pieces that can pass.
- Ureteroscopy: a thin scope is passed through the bladder into the ureter or kidney, and a laser breaks up or removes the stone. A temporary stent may be placed afterwards.
- Percutaneous nephrolithotomy (PCNL): used for large or complex stones, removed through a small incision in the back.
How to prevent kidney stones
Drink plenty of fluids
This is the single most important step. Many people with a history of stones are advised to drink enough to make about 2 to 2.5 liters of urine a day. Your clinician can give you a personal target. Water is the best choice.
Cut back on sodium
High sodium intake increases calcium in the urine. Limit processed foods, canned soups, fast food and salty snacks.
Do not cut out calcium
It may sound surprising, but getting a normal amount of calcium from food helps prevent calcium oxalate stones, because calcium binds oxalate in the gut. Avoid high-dose calcium supplements unless advised.
Be smart about oxalate
If you form calcium oxalate stones, your clinician may suggest limiting very high-oxalate foods such as spinach, rhubarb, beets, nuts and almond-based products. Eating calcium-rich foods with oxalate-containing foods also helps.
Moderate animal protein
Large amounts of red meat, poultry, eggs and seafood can raise uric acid and lower citrate, a natural stone inhibitor.
Eat more fruits and vegetables
They provide citrate and potassium, which help prevent stones.
Limit sugary drinks
Drinks sweetened with sugar or high-fructose corn syrup are linked to higher stone risk.
Medicines for prevention
Depending on your stone type and urine tests, your clinician may prescribe thiazide diuretics, potassium citrate or allopurinol.
The National Institute of Diabetes and Digestive and Kidney Diseases has more information on stone types and prevention.
Frequently asked questions
How long does it take to pass a kidney stone?
Small stones may pass in days to a few weeks. Larger stones can take longer or may need treatment.
Does lemon water help?
Lemon juice contains citrate, which can help prevent some stones. It works best as part of drinking more fluids overall rather than as a cure.
Will I get another kidney stone?
The chance of a repeat stone is significant, but drinking more fluid and following targeted diet changes can greatly lower it.
The bottom line
Kidney stones are painful but usually treatable, and most small ones pass on their own. Staying well hydrated, eating less sodium and keeping a normal calcium intake are the foundation of prevention. Seek urgent care for severe pain, fever or difficulty urinating.
This article is for general information and is not a substitute for advice from a qualified healthcare professional.