Kidney stones are hard crystals formed from salts in the urine inside the kidney. They may stay there or move into the ureter and cause renal colic. They are more common in hot countries because of fluid loss. Most small stones pass on their own, and larger stones or those causing complications have effective treatments.
Medically reviewed by Prof. Dr. Samir Ahmed Al-Samarrai, consultant urologist. Last reviewed:
Types of stones
- Calcium stones (calcium oxalate or phosphate): the most common type.
- Uric acid stones: linked to gout and some diets; some dissolve with medicine.
- Infection (struvite) stones: linked to repeated urinary infections.
- Cystine stones: rare and inherited.
Knowing the stone type, by analysing it after it passes or is removed, helps prevent recurrence.
Causes and risk factors
- Not drinking enough, heat and heavy sweating.
- A diet high in salt and animal protein.
- Obesity, diabetes and gout.
- A family history or a previous stone.
- Repeated urinary infections and some gland disorders such as overactive parathyroid glands.
- Some medicines and supplements.
Symptoms
- Renal colic: severe pain in the side or lower back that comes in waves and spreads to the lower abdomen, testicle or vulva.
- Nausea and vomiting.
- Blood in the urine, visible or only on testing.
- Frequent, burning urination as the stone nears the bladder.
- Sometimes no symptoms, especially with small stones inside the kidney.
When to go to the emergency department
- Fever or shivering with renal colic.
- Pain not controlled by painkillers, or persistent vomiting.
- Passing very little or no urine.
- A stone with a single kidney, or during pregnancy.
Diagnosis
- Low-dose non-contrast CT within 24 hours for adults with suspected renal colic, as NICE recommends.
- Ultrasound in pregnancy and for children, and for following some cases. Read about urinary tract ultrasound.
- Urine test for blood and infection. Read about the urine test.
- Blood tests for kidney function, calcium and uric acid.
- Stone analysis after it passes or is removed.
Treatment in brief
Treatment depends on the stone’s size and position and on symptoms: painkillers and watchful waiting for small stones, medicines that help lower ureteric stones pass, or shockwave or endoscopic treatment when needed. Read kidney and ureteric stone treatment.
Prevention
NICE advises adults to drink 2.5 to 3 litres of water a day, add fresh lemon juice to water, avoid fizzy drinks, keep salt to no more than 6 g a day, and keep a normal calcium intake rather than cutting it.
Articles on kidney stones
- Kidney stone prevention: water and diet
- Kidney sand and crystals in urine
- Kidney stones in women
- Kidney stone size: when will it pass?
- Renal colic: symptoms, treatment and emergency signs
- Treating kidney and ureter stones by flexible and laser endoscopy and primary prevention
- Kidney stones: causes and prevention during Ramadan
- Blood in urine
- Kidney and ureteric stone treatment
Frequently asked questions
What are the symptoms of a kidney stone?
The best known is renal colic: severe pain in the side or lower back that spreads to the lower abdomen, testicle or vulva, with nausea or vomiting and sometimes blood in the urine. Some stones in the kidney cause no symptoms and are found by chance.
Is fever with a kidney stone dangerous?
Yes. Fever or shivering with renal colic can mean infection behind a stone blocking the ureter. This is an emergency that needs urgent care, as the kidney may need draining quickly.
What is the best test for kidney stones?
Low-dose non-contrast CT is the most accurate test for adults according to NICE; ultrasound is preferred in pregnancy and for children, along with urine and blood tests.
Do kidney stones come back?
They can recur in many people, so prevention with enough water and less salt helps. People with recurrent stones may need stone analysis and special urine tests.
Does dietary calcium cause stones?
Cutting down on dietary calcium is not advised. NICE recommends keeping a normal daily calcium intake, because restricting it can increase some types of stones.
Sources
Book a consultation
Prof. Al-Samarrai and Dr. Amer Mousa assess kidney and ureteric stones at Prof. Al-Samarrai Medical Center, Dubai Healthcare City, and discuss the options that suit your case. Medical consultations are confidential.
This information is for health education and does not replace a medical examination. See our medical content policy.