Overview
Kidney stones are solid mineral deposits that form inside the kidneys when certain substances in urine become concentrated. They range from tiny grains to stones the size of a golf ball. Small stones pass spontaneously; larger stones may require medical procedures. They cause intense pain when moving through the urinary tract.
How common is it?
Kidney stones affect approximately 1 in 11 adults at some point. They are roughly twice as common in men as in women and most commonly present between age 30 and 60. Recurrence is high: about 50% have a second stone within 10 years without preventive measures.
Causes and risk factors
Stones form when the urine contains high concentrations of stone-forming minerals and insufficient inhibitors of crystallisation. The most common type is calcium oxalate.
Common risk factors
- Insufficient fluid intake (most important modifiable factor)
- High-oxalate diet (spinach, nuts, chocolate) for oxalate stones
- High salt and protein intake raising urinary calcium
- Obesity and type 2 diabetes
- Hyperparathyroidism (raises blood and urinary calcium)
- Recurrent urinary infections (struvite stones)
- Gout and high purine diet (uric acid stones)
- Family history
- Inflammatory bowel disease (increased oxalate absorption)
Symptoms
- Severe, colicky flank pain radiating to the groin and genitals (renal colic)
- Pain comes in waves, lasts 20 to 60 minutes, and is often the most severe pain a person experiences
- Nausea and vomiting
- Blood in urine (haematuria)
- Urinary urgency and frequency if stone in lower ureter
- Fever and rigors if infection is present (this is an emergency)
When to see a doctor
A stone with fever and rigors is an emergency (obstructed infected kidney) requiring immediate hospital admission. Seek same-day assessment for renal colic not settling with analgesia, or if only one functioning kidney.
Diagnosis
Non-contrast CT KUB is the gold standard (sensitivity 95 to 98%). Ultrasound is used in pregnancy. Urine dipstick typically shows blood. Metabolic workup: serum calcium, urate, creatinine, 24-hour urine collection for recurrent stone formers.
Treatments
Pain management and passage
NSAIDs (diclofenac) are first-line analgesia; more effective than opioids for renal colic. Alpha-blockers (tamsulosin) relax the ureteric smooth muscle, speeding spontaneous passage. Stones under 5mm pass spontaneously in about 70% of cases.
Extracorporeal shock wave lithotripsy (ESWL)
High-energy shock waves fragment the stone externally. Outpatient procedure. Best for stones under 2cm in kidney or upper ureter.
Ureteroscopy and laser lithotripsy
A flexible scope is passed via the urethra to the stone and laser pulses fragment it. Fragments pass in urine. Highly effective for mid and lower ureteric stones.
Percutaneous nephrolithotomy (PCNL)
Surgical removal via a tract through the back into the kidney. Used for large stones (above 2cm) or those not amenable to ESWL or ureteroscopy.
Self-care and lifestyle
- Drink at least 2.5 to 3 litres of water daily to keep urine dilute (most important prevention)
- Reduce salt intake (below 6g daily)
- Moderate dietary oxalate for oxalate stone formers
- Avoid crash diets and excessive vitamin C or vitamin D supplementation
- Normal calcium intake (very low calcium diet paradoxically increases oxalate absorption)
Prevention
Adequate hydration is the single most effective prevention. Specific dietary and pharmacological measures (potassium citrate, thiazides, allopurinol) depend on the stone type and are guided by metabolic workup.