Kidney Stones: Prevention, Pain Relief and When Surgery Is Needed
Kidney stone pain is routinely described as among the worst pain people experience, and roughly half of those who have one stone will form another within ten years. Both facts argue for taking prevention seriously after the first episode.
How stones form
Urine carries dissolved minerals. When their concentration exceeds what the fluid can hold, or when natural inhibitors such as citrate are depleted, crystals form and aggregate. Low urine volume is the single most common underlying factor across all stone types.
Types
- Calcium oxalate, around 70 to 80 percent. Associated with low fluid intake, high sodium, high oxalate foods and low dietary calcium
- Calcium phosphate, often associated with renal tubular acidosis or hyperparathyroidism
- Uric acid, around 5 to 10 percent, favoured by persistently acidic urine, high purine intake, gout, obesity and diabetes. These can sometimes be dissolved medically
- Struvite, linked to urea-splitting urinary infections. These can grow large and fill the collecting system as staghorn stones
- Cystine, rare and inherited, presenting young and recurring
The pain pattern
Classic renal colic begins suddenly, in waves, in the flank or loin, and radiates around and down toward the groin, testicle or labium as the stone moves. The person cannot find a comfortable position and tends to move about, which distinguishes it from peritonitis where people lie still.
Associated features include nausea and vomiting, visible or microscopic blood in the urine, urinary frequency and urgency as the stone approaches the bladder, and pain on passing urine.
Red flags requiring urgent care
- Fever or chills with the pain, which may indicate an infected obstructed kidney and is a surgical emergency
- A single functioning kidney, or a transplanted kidney
- Pain uncontrolled by oral medication
- Persistent vomiting preventing fluid intake
- Reduced urine output or anuria
- Known kidney impairment
- Pregnancy
Diagnosis
Non-contrast CT of the kidneys, ureters and bladder is the most accurate test and shows size, position and density. Ultrasound is preferred in pregnancy and children and for follow-up to limit radiation. Urinalysis, blood tests for kidney function, calcium and uric acid, and straining the urine to capture the stone for analysis all guide prevention.
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Treatment of an acute stone
Pain relief. Non-steroidal anti-inflammatories are generally more effective than opioids for renal colic, where kidney function allows.
Fluids. Enough to stay hydrated; forcing large volumes does not push the stone out faster.
Medical expulsive therapy. Alpha blockers such as tamsulosin may help passage of larger distal ureteric stones.
Watchful waiting. Stones under about 5 mm pass spontaneously in the majority of cases, usually within a few weeks. Between 5 and 10 mm, passage is less likely. Above 10 mm, intervention is usually required.
Procedures:
- Extracorporeal shock wave lithotripsy, breaking the stone with external shock waves
- Ureteroscopy with laser fragmentation, passing a scope up through the bladder
- Percutaneous nephrolithotomy, for large or staghorn stones, through a small flank incision
- Emergency drainage with a stent or nephrostomy when there is infection with obstruction, with stone removal deferred until the infection is treated
Prevention, where most of the benefit lies
Fluid. Aim for a urine output of at least 2.5 litres daily, which usually means drinking around 3 litres, more in hot weather or physical work. The practical test is pale, almost colourless urine. This single measure roughly halves recurrence.
Do not restrict dietary calcium. This is counter-intuitive but important: calcium in food binds oxalate in the gut so it is excreted in stool rather than urine. Low-calcium diets increase stone risk. Calcium supplements, taken apart from meals, are a different matter and may increase risk, so take them with food if prescribed.
Reduce sodium. High salt increases urinary calcium excretion.
Moderate oxalate if you form calcium oxalate stones: spinach, beetroot, rhubarb, nuts, chocolate, tea in large quantities, soy and sweet potato are the main contributors. Pair them with a calcium-containing food rather than eliminating them.
Moderate animal protein, which raises uric acid and lowers citrate.
Add citrate. Lemon or lime juice in water, and oranges, raise urinary citrate, a natural stone inhibitor. Potassium citrate is prescribed for some patients.
Lose excess weight, and treat diabetes, gout and hyperparathyroidism.
Avoid high-dose vitamin C supplements, which are converted to oxalate.
Metabolic evaluation
After a second stone, a stone in a child, bilateral stones, a single kidney, or a strong family history, a 24-hour urine collection measuring volume, calcium, oxalate, citrate, uric acid, sodium and pH identifies the specific driver and allows targeted treatment. Stone analysis, if you can catch the stone, is the cheapest and most informative test available.
This is general information. Severe flank pain with fever needs emergency assessment, not home management.