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Kidney Stones

Kidney stones are one of the most painful conditions there is — but most can be treated without surgery, and many can be prevented.

What are kidney stones?

Kidney stones are hard deposits of minerals and salts that form inside the kidneys. They develop when substances in urine — like calcium, oxalate, and uric acid — become too concentrated and crystallize. Over time, these crystals grow into stones that range in size from a grain of sand to a golf ball.

Small stones often pass on their own through the urinary tract without causing many problems. Larger stones can get stuck and cause intense pain, blockage, and infection.

About 1 in 10 people will develop a kidney stone at some point in their life. Once you've had one, the chance of getting another within 10 years is about 50% — which is why prevention matters.

Types of kidney stones

Calcium oxalate stones (most common — ~80%) — Form when calcium and oxalate combine in urine. Risk factors include dehydration, high-oxalate diet, and certain medical conditions.
Uric acid stones (~10%) — Form when urine is too acidic. Common in people with gout, diabetes, or who eat very high-protein diets.
Struvite stones — Form after recurrent urinary tract infections. Can grow very large quickly.
Cystine stones — Rare, caused by a genetic disorder (cystinuria) that causes the kidneys to leak too much of the amino acid cystine.

Symptoms

When a stone moves from the kidney into the ureter (the tube connecting kidney to bladder), it causes:

  • Sudden, severe pain in the back or side — often described as the worst pain imaginable, worse than childbirth or surgery
  • Pain that radiates to the lower abdomen and groin as the stone moves
  • Pain that comes in waves and fluctuates in intensity
  • Blood in the urine (pink, red, or brown)
  • Nausea and vomiting from the intense pain
  • Frequent, painful urination when the stone reaches the bladder
  • Fever and chills if infection is present — seek emergency care immediately

Treatment

For small stones (usually less than 5mm)

Most small stones pass on their own within a few days to a few weeks. Treatment focuses on managing pain (NSAIDs or stronger medications) and staying well hydrated (2–3 liters of water per day to help flush the stone). Your doctor may prescribe a medication called an alpha-blocker (tamsulosin) that relaxes the ureter and helps the stone pass faster.

For larger stones or stones that won't pass

  • Shock wave lithotripsy (SWL) — Sound waves from outside the body break the stone into smaller pieces that can then pass in urine. Non-invasive, done as an outpatient procedure.
  • Ureteroscopy — A thin scope is passed up through the urethra and bladder to the stone, which is then broken up with a laser or removed. Most common procedure for stones in the ureter or kidney.
  • Percutaneous nephrolithotomy (PCNL) — For very large stones. A small incision in the back allows direct removal of the stone. Done under general anesthesia.

Prevention — the most important part

Once you've had a kidney stone, preventing the next one is critical. What works depends on the type of stone — which is why analyzing the stone (if you can catch it) and doing a 24-hour urine collection is so valuable.

Drink more water — The single most effective prevention. Aim for 2.5–3 liters of fluid per day. Your urine should be pale yellow, not dark.
Reduce sodium — High salt intake increases calcium in urine. Limit to 2,300mg sodium per day.
Don't avoid calcium — Counterintuitively, eating normal amounts of dietary calcium (from food, not supplements) actually reduces calcium oxalate stone risk by binding oxalate in the gut.
Limit high-oxalate foods — Spinach, rhubarb, almonds, and chocolate if you form calcium oxalate stones.
Limit animal protein — Red meat, poultry, and shellfish increase uric acid and can promote stone formation.
If you pass a stone, try to collect it in a strainer and bring it to your doctor. Stone analysis tells us exactly what type it is, which guides the most effective prevention strategy.
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