Kidney Stones

Kidney stones are hard mineral deposits that form inside the kidneys when substances in the urine — such as calcium, oxalate, and uric acid — become too concentrated and crystallize. They affect roughly 1 in 10 Americans, and rates have been rising over the past several decades. Stones range from a grain of sand to larger than a marble, and they can cause excruciating pain when they move from the kidney into the ureter, the narrow tube that carries urine to the bladder.

Most people experience their first stone between ages 40 and 60, and men are affected more often than women (about 11% vs. 7%). If you have had one stone, you have approximately a 50% chance of forming another within five years without preventive measures — which is why evaluation and long-term prevention are just as important as treating the stone itself.

Types of Kidney Stones

Knowing which type of stone you have helps guide both treatment and prevention:

Calcium oxalate stones are the most common, accounting for about 70–80% of all kidney stones. They form when calcium combines with oxalate in the urine. Contrary to popular belief, restricting calcium is usually not the answer — in fact, too little dietary calcium can increase your risk.

Uric acid stones make up about 5–10% of stones and are more common in people with gout, diabetes, or diets very high in animal protein. They form in acidic urine and can often be prevented or even dissolved by making the urine more alkaline.

Struvite stones (also called infection stones) are caused by chronic urinary tract infections. Certain bacteria produce ammonia that raises urine pH, encouraging the growth of large, branching stones that can fill the entire kidney. Treating the underlying infection is essential.

Cystine stones are the rarest type, caused by an inherited condition called cystinuria that leads to excessive cystine in the urine. These stones tend to form at a young age and require specialized, lifelong management.

Symptoms

A stone sitting quietly in the kidney may cause no symptoms at all. Pain typically begins when a stone enters the ureter and obstructs urine flow, causing the kidney to swell and the ureter to spasm. Common symptoms include:

Severe, sudden pain in the flank (side and back below the ribs) that may radiate to the lower abdomen and groin. This pain, often called renal colic, comes in intense waves and is widely described as one of the most painful experiences a person can have.

Blood in the urine (hematuria) — urine may appear pink, red, or brown.

Nausea and vomiting are common during acute stone episodes due to shared nerve pathways between the kidney and the stomach.

Urinary urgency, frequency, or burning — especially as the stone nears the bladder.

Fever and chills signal a possible urinary tract infection alongside the stone — a serious combination that requires immediate medical attention.

Risk Factors

Several factors increase your chance of developing kidney stones:

Dehydration is the single most common cause. When you don't drink enough fluids, your urine becomes concentrated, allowing minerals to crystallize more easily.

Diet plays a major role. High sodium intake forces more calcium into the urine. Diets very high in animal protein increase uric acid and reduce citrate, a natural stone inhibitor. Excess sugar and processed foods also raise risk.

Family and personal history. If a parent or sibling has had stones, your risk is significantly higher. A prior stone roughly doubles your lifetime risk.

Obesity and metabolic syndrome — higher BMI, diabetes, and hypertension are all independently associated with stone formation.

Certain medical conditions such as hyperparathyroidism, inflammatory bowel disease, chronic UTIs, and gout can predispose to stones.

When a kidney stone is suspected, a non-contrast CT scan is the gold standard for diagnosis. It quickly identifies the stone's size, location, and number with high accuracy, and it does not require contrast dye. A CT scan also helps rule out other causes of abdominal pain.

A urinalysis checks for blood in the urine, signs of infection, and urine pH. Blood work evaluates kidney function, calcium levels, and uric acid. Together, these results help Dr. Radtke determine whether the stone is likely to pass on its own or whether intervention is needed.

If you have passed a stone, stone analysis — sending the stone to a laboratory — reveals its exact composition and is invaluable for guiding prevention. Always strain your urine and save any stone fragments you pass.

Whether a stone can pass without surgery depends primarily on its size and location:

Stones 4 mm or smaller have a very high chance of passing spontaneously — most will pass within days to a few weeks with hydration and pain management.

Stones 5–10 mm have a moderate chance of passing, especially if located in the lower (distal) ureter near the bladder. A medication called tamsulosin (an alpha-blocker) can relax the ureter and significantly improve the odds of passage. This is called medical expulsive therapy and is typically tried for up to 4–6 weeks.

Stones larger than 10 mm rarely pass on their own and usually require a procedure.

Other factors also matter: stones that have not moved after several weeks, stones causing persistent pain or vomiting, stones blocking a kidney with signs of infection, or stones in patients with a solitary kidney all warrant early intervention. Dr. Radtke will discuss the options and timeline with you so you can make an informed decision about waiting versus proceeding with treatment.

Because the recurrence rate for kidney stones can reach 50% within five years, prevention is a critical part of stone care. Dr. Radtke provides a thorough approach to reduce your risk of future stones.

Hydration

Increasing fluid intake is the single most effective prevention strategy. The goal is to produce at least 2.5 liters of urine per day — enough that your urine stays light yellow or clear. Water is ideal. Research shows that adequate hydration alone can reduce stone recurrence by up to 50%.

Dietary Modifications

Reduce sodium. High salt intake is one of the biggest dietary drivers of calcium stones because it forces more calcium into the urine. Aim for less than 2,300 mg of sodium per day.

Get enough calcium from food. It may sound counterintuitive, but dietary calcium (from dairy, leafy greens, or fortified foods) actually reduces stone risk by binding oxalate in the gut before it reaches the kidneys. Aim for 1,000–1,200 mg daily. Calcium supplements, however, may increase risk if not taken with meals.

Moderate animal protein. Diets very high in red meat, poultry, and seafood increase uric acid production and lower citrate, a natural stone inhibitor.

Limit oxalate-rich foods if you form calcium oxalate stones. Common high-oxalate foods include spinach, rhubarb, beets, nuts, and chocolate. Eating these foods with calcium-rich foods helps reduce oxalate absorption.

24-Hour Urine Metabolic Workup

For recurrent stone formers or patients with high-risk features, Dr. Radtke recommends a 24-hour urine collection — a detailed analysis that measures urine volume, calcium, oxalate, citrate, uric acid, sodium, and pH. This test identifies the specific metabolic abnormalities driving your stone formation and guides targeted treatment. Despite its proven value, studies show that only 7–16% of stone patients undergo this evaluation — a gap Dr. Radtke works to close.

Medications for Prevention

When dietary changes alone are not enough, medications can significantly reduce recurrence. Options include thiazide diuretics (which lower urine calcium), potassium citrate (which raises urine citrate and pH), and allopurinol (which lowers uric acid). The right medication is chosen based on your 24-hour urine results and stone type.

Most kidney stones, while painful, can be managed in the outpatient setting. However, certain situations require immediate emergency care:

Fever or chills with a known or suspected stone — this combination suggests an infected, obstructed kidney (obstructive pyelonephritis) and can rapidly progress to sepsis. Emergency drainage of the kidney, usually with a ureteral stent, is often needed.

Severe pain that cannot be controlled with over-the-counter or prescribed pain medications.

Persistent nausea and vomiting that prevent you from keeping down fluids or medications.

Inability to urinate or a significant decrease in urine output.

Stone in a solitary kidney — if you have only one functioning kidney and it becomes obstructed, prompt intervention is essential to protect kidney function.

If you are experiencing manageable pain and have no signs of infection, a scheduled appointment with Dr. Radtke is appropriate. He will evaluate your stone, discuss your options, and develop a plan — whether that involves watchful waiting, medical therapy, or a procedure.