Kidney Stones: Symptoms, Causes, and Treatment
Also known as: Renal Calculi, Nephrolithiasis
Kidney Stones: What Are They?
Kidney stones, also called renal calculi or nephrolithiasis, are solid mineral deposits that form in the kidneys. In the United States, about 11% of men and 6% of women develop a kidney stone at least once in their lifetime, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and these rates have been rising. Stones are more common in men than women, and most occur between ages 20 and 50. Recurrence is common: without prevention, nearly half of patients form another stone within 10 years.
Causes and Risk Factors
Stones form when urine becomes supersaturated with minerals. Main causes include:
- Chronic dehydration, which reduces urine volume
- A diet high in salt, animal protein, or oxalates (spinach, chocolate, nuts)
- Metabolic disorders: high urine calcium, uric acid, or oxalate levels
- A family history of kidney stones
- Certain conditions: hyperparathyroidism, Crohn’s disease, metabolic syndrome
- Certain medications and high-dose vitamin C supplements
- Hot climates, which increase sweating and urine concentration
Symptoms
The hallmark symptom is renal colic: sudden, severe flank pain that radiates toward the groin and genitals. This pain is often described as one of the most intense a person can experience. It’s frequently accompanied by:
- Nausea and vomiting
- Hematuria (blood in the urine, visible or microscopic)
- Frequent urge to urinate
- Burning during urination
- Restlessness (unable to find a comfortable position)
- Fever if there’s an associated infection (obstructive pyelonephritis, a medical emergency)
Diagnosis
Doctors diagnose kidney stones based on history and physical exam, confirmed with additional tests:
- Non-contrast CT scan of the abdomen/pelvis: the gold-standard test, with about 98% sensitivity for detecting stones
- Renal ultrasound: first choice for pregnant women and children
- Urinalysis and urine culture to detect an associated infection
- Blood tests: creatinine, calcium, uric acid
- Analysis of a passed stone to identify its composition
Treatments
Treatment depends on the stone’s size, location, and composition:
- Conservative medical management: for smaller stones likely to pass on their own (about 90% of stones under 5 mm do), with strong pain relievers (NSAIDs, opioids), alpha-blockers to help the stone pass, and plenty of fluids
- Extracorporeal shock wave lithotripsy (ESWL): breaks up the stone using shock waves, no incision needed, for stones up to about 20 mm
- Ureteroscopy: a scope is passed through the natural urinary tract to break up or remove the stone with a laser
- Percutaneous nephrolithotomy (PCNL): minimally invasive surgery reserved for larger stones (over 20 mm)
- Treating the underlying cause: based on metabolic workup (allopurinol for uric acid stones, potassium citrate, thiazide diuretics)
Prevention
Prevention relies mainly on diet and lifestyle:
- Stay well hydrated: drink enough fluid to produce about 2.5 liters (85 oz) of urine a day, more in hot weather or with physical activity
- Limit sodium intake to less than 2,300 mg per day (about 1 teaspoon of salt), per American Heart Association guidance, and reduce animal protein
- Limit oxalate-rich foods (spinach, rhubarb, chocolate) if you have calcium oxalate stones
- Maintain normal dietary calcium intake (don’t cut out dairy)
- Avoid sugary drinks and sodas
- Reach a healthy weight if overweight or obese
- Regular urology follow-up with a 24-hour urine test can help tailor prevention to your specific stone type
When Should You See a Doctor?
Seek emergency care for severe flank pain, fever combined with pain (possible obstructive infection), complete inability to urinate, or if you can’t keep any food down. Isolated blood in the urine or recurring flank pain also warrants prompt medical evaluation.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), U.S. lifetime prevalence in men and women
- National Kidney Foundation, recurrence risk (about 1 in 2 or more) and hydration target (about 2.5 liters of urine a day)
- Acute Renal Colic, StatPearls (NCBI Bookshelf), non-contrast CT sensitivity (98%), age distribution (over 70% at ages 20 to 50), and ultrasound as first-line imaging in pregnancy
- Renal Calculi, Nephrolithiasis, StatPearls (NCBI Bookshelf), recurrence timeframe and spontaneous passage of stones under 5 mm
- Guideline of guidelines for kidney and bladder stones (PMC), stone-size treatment thresholds (SWL/ureteroscopy up to 20 mm, PCNL over 20 mm) and ultrasound as first-line imaging in pregnancy and children
- American Heart Association, daily sodium recommendations