Kidney stones: causes, symptoms and prevention

Kidney stones form when minerals in urine crystallise and can cause very sharp pain in the flank or back. Small stones often pass on their own in the urine, while large ones may need intervention. The most effective prevention is drinking enough water.

Symptoms

Small stones sometimes pass with no symptoms. When a stone moves and blocks the urinary tract, very sharp pain (renal colic) develops:

• Sharp, wave-like pain in the flank or back
• Pain spreading to the groin or genital area
• Blood or cloudiness in the urine, a strong smell
• Frequent, painful urge to urinate, nausea and vomiting

Why do stones form?

When substances such as calcium, oxalate or uric acid become too concentrated in the urine, they crystallise and over time turn into stones. The biggest causes are drinking too little water (concentrated urine) and high salt intake. Some metabolic conditions, a hereditary tendency and recurrent urinary infections also raise the risk.

What to do when passing a stone

Small stones (usually under 5 mm) often pass on their own with plenty of water. To manage pain a doctor may prescribe pain relief and sometimes a medication that widens the urinary tract. Keeping a passed stone to show your doctor helps identify its type.

Prevention

Those who have passed a stone are at higher risk of another, so prevention matters:

• Drink 2–2.5 litres of water a day (urine should be pale)
• Cut down on salt and animal protein
• Be moderate with oxalate-rich foods (spinach, tea, nuts)
• Favour citrus drinks (lemon water)
• Get enough calcium from food (not excessive supplements)

Treatment options

For large or obstructing stones a urologist may use laser/shockwave lithotripsy, endoscopic or surgical methods to break or remove the stone. The size, location and composition of the stone determine the treatment.

When to see a doctor

Seek urgent urology care for unbearable pain, pain with fever (sign of infection), non-stop vomiting, or blood in the urine.

Frequently asked questions

Do kidney stones come back?

Yes, people who have passed a stone are at higher risk of recurrence; good hydration and diet lower that risk.

Which water is better?

Ordinary drinking water is fine; what matters is the total amount — your urine should be pale.

Should I cut out calcium?

No. Cutting dietary calcium can actually raise stone risk; the problem is excessive calcium supplements and too little water.

This article is for information only and does not replace a doctor's advice.