A kidney stone is a hard, pebble-like clump of minerals and salts that forms inside the kidney when urine becomes too concentrated. Stones can sit quietly in the kidney or travel down the urinary tract, causing severe pain as they pass. They range in size from a grain of sand to a golf ball.
Nearly 1 in 10 people will develop a kidney stone in their lifetime (Cleveland Clinic / Urology Care Foundation), and about 9.9% of US adults report a history of stones (NIH).
Causes & risk factors
- Not drinking enough water, or chronic dehydration
- A high-sodium, high-animal-protein, or high-sugar diet
- Family history of kidney stones
- Obesity and metabolic conditions such as diabetes or gout
- Certain medications (diuretics, calcium antacids) and excess vitamin C
- Underlying conditions such as hyperparathyroidism or inflammatory bowel disease
Symptoms to watch for
- Sharp, wave-like pain in the back, side, lower belly, or groin
- Blood in the urine (pink, red, or brown)
- Nausea and vomiting
- Frequent urge to urinate, or a burning sensation
- Cloudy or foul-smelling urine
- Fever or chills with pain, or inability to urinate — suggests infection or blockage and needs emergency care
How it's diagnosed
- Urinalysis (checks for blood, crystals, or infection)
- CT scan — the most definitive imaging test
- Ultrasound or plain X-ray
- Blood tests for kidney function and calcium levels
Treatment options
- Hydration + pain relief: for small stones, about 80% pass on their own within 1–2 weeks (Cleveland Clinic).
- Medical expulsive therapy: medication such as tamsulosin relaxes the ureter to help a stone pass naturally.
- Shockwave lithotripsy (SWL): non-invasive sound waves break the stone apart from outside the body.
- Ureteroscopy (URS): a thin scope passed through the natural urinary channel lasers the stone into fragments.
- RIRS (Retrograde Intrarenal Surgery): a flexible scope reaches inside the kidney via the natural urinary tract for laser fragmentation — no incision, same-day discharge.
- PCNL (Percutaneous Nephrolithotomy): a small back incision gives direct kidney access — reserved for large or complex stones over 20mm.
Outlook & prevention
Most stones pass on their own or are treated successfully with minimally invasive procedures and a quick recovery. Recurrence is common though, so prevention matters: aim for enough fluids to produce 2–2.5 litres of urine a day, moderate animal protein and sodium, and maintain a healthy weight.
- Severe pain that doesn't ease, or pain together with fever or chills
- Inability to urinate, or passing only small amounts
- Visible blood in the urine