Kidney Stones: Symptoms, Causes, Treatment, Prevention and Diet

Kidney stones are hard deposits of minerals and salts that form inside the kidneys. They are common, particularly in hot climates, and rates are high in parts of South Asia, including Sri Lanka. Small stones may cause no symptoms, but when a stone moves into the ureter (the tube leading from the kidney to the bladder) it can cause one of the most severe pains known, called renal colic.

Symptoms

• Severe, sharp, cramping pain in the side and back below the ribs, that may spread to the lower abdomen and groin. It comes in waves, lasts 20-60 minutes and the person cannot get comfortable.
• Blood in the urine (pink, red or brown), or invisible blood found on testing
• Nausea and vomiting
• Burning, frequent or urgent urination
• Cloudy or foul-smelling urine
• Fever and chills if infection is present (an emergency)

Stones that stay in the kidney may produce no pain and are found by chance on scans.

Why stones form

Stones form when urine contains too much of certain substances (calcium, oxalate, uric acid) and not enough fluid to dilute them, or too little of substances that block crystals, such as citrate.

Types:

• Calcium oxalate (most common, about 80%)
• Calcium phosphate
• Uric acid, linked to gout, acidic urine and high-purine diets. See high uric acid and gout
• Struvite (infection stones)
• Cystine (rare, inherited)

Risk factors

• Not drinking enough water, hot climate, sweating and outdoor work
• High salt and animal protein intake, and sugary drinks
• Overweight, diabetes and metabolic syndrome
• Family history or previous stones
• Repeated urinary infections (see UTI)
• Medical conditions: gout, hyperparathyroidism, inflammatory bowel disease, kidney problems, and urinary tract abnormalities
• Medicines and supplements: high-dose vitamin C or D or calcium supplements, some diuretics and antacids
• Gastric bypass surgery

Diagnosis

• Urine tests: blood, infection, crystals
• Blood tests: kidney function, calcium, uric acid
• Imaging: a low-dose CT scan is the most accurate, and ultrasound (with or without X-ray) is often used first, especially in pregnancy and children
• Stone analysis after passing or removal, and 24-hour urine tests for recurrent stone formers

Treatment of a stone attack

At home (for small stones and no complications):

• Pain relief: NSAIDs such as diclofenac or ibuprofen are most effective, if kidneys and stomach allow, and paracetamol if not. Avoid NSAIDs if you could have dengue.
• Drink plenty of fluids. There is no need to force very large amounts.
• Alpha-blockers such as tamsulosin may help larger ureteric stones (5-10 mm) pass in some patients.
• Strain the urine to catch the stone for analysis, if advised.
• Anti-sickness medicine if needed.

In hospital or by a urologist:

• Shock wave lithotripsy (ESWL): shock waves break the stone into smaller pieces, for stones up to about 1-2 cm.
• Ureteroscopy with laser fragmentation (URS): a thin scope passed through the bladder to reach and break the stone.
• Percutaneous nephrolithotomy (PCNL): keyhole surgery for large kidney stones.
• Stent placement to relieve blockage, particularly with infection.
• Open surgery is rarely needed.

Emergency: go to hospital immediately if

• Severe pain with fever, chills or shivering (infected blocked kidney, which can cause sepsis)
• Unable to pass urine, or very little urine
• Pain that is not controlled by painkillers, or persistent vomiting
• You have a single kidney, kidney disease or are pregnant
• Dizziness, confusion or fainting

How to prevent kidney stones

1. Drink more water: aim for about 2.5-3 litres a day, so that you pass at least 2-2.5 litres of pale urine. Spread it through the day and drink extra in hot weather or with exercise. Use our water intake calculator. If you have heart or kidney failure, follow your doctor's fluid limits.
2. Reduce salt: high sodium raises urinary calcium. Aim for less than 5 g a day. See heart-healthy diet in Sri Lanka.
3. Eat normal calcium from food, such as milk, curd and small fish with bones, and avoid unnecessary calcium supplements.
4. Moderate animal protein: reduce large portions of red meat, poultry, fish and eggs, especially if you have uric acid or calcium stones.
5. Limit very high-oxalate foods if you have oxalate stones: spinach, rhubarb, beetroot, nuts, chocolate, and large amounts of strong tea. Eat them with calcium-containing foods rather than avoiding them completely.
6. Add citrate: lime or lemon juice in water, or potassium citrate if prescribed.
7. Cut sugary drinks and fructose, and keep a healthy weight. See how to lose weight safely.
8. Treat urine infections and underlying conditions such as gout, diabetes and parathyroid disease.
9. Take medicines as prescribed: thiazide diuretics, potassium citrate or allopurinol, depending on stone type.

Follow-up

After a stone, ask your doctor about stone analysis and metabolic tests, and about follow-up imaging for any remaining fragments. Check your kidney function, and use our eGFR calculator to understand results.

When to see a doctor

See a doctor if you have blood in your urine, recurring back or flank pain, repeated urinary infections or a previous stone. Seek emergency care for the warning signs above.

References

• European Association of Urology: guidelines on urolithiasis
• American Urological Association: surgical management of stones and medical management guidelines
• NICE guideline NG118: renal and ureteric stones, assessment and management
• World Health Organization / International Society of Nephrology: kidney health guidance