Renal Calculi (Kidney Stones)

Causes

• Dehydration: Not drinking enough water is a leading cause, as it reduces urine volume and allows stone-forming substances to become more concentrated.
• Diet:
  • High sodium intake: Can increase the amount of calcium in your urine.
  • High animal protein intake: Can increase uric acid levels and reduce citrate, which helps prevent stones.
  • High oxalate foods: Foods like spinach, chocolate, nuts, and tea are high in oxalate, which can bind with calcium to form stones.
• Obesity: Higher body mass index (BMI) has been linked to an increased risk of kidney stones.
• Digestive Diseases and Surgery: Conditions like Crohn's disease, ulcerative colitis, or gastric bypass surgery can affect calcium and water absorption, increasing stone risk.
• Medical Conditions:
  • Hyperparathyroidism: Leads to high calcium levels in the blood and urine.
  • Renal tubular acidosis: A condition in which the kidneys fail to excrete acids into the urine, leading to an overly alkaline urine and the formation of calcium phosphate stones.
  • Cystinuria: A rare genetic disorder that causes the amino acid cystine to leak into the urine, forming cystine stones.
  • Urinary tract infections (UTIs): Some UTIs can produce struvite stones.
  • Gout: Can lead to higher uric acid levels, increasing the risk of uric acid stones.
• Certain Medications: Diuretics, some anti-seizure medications, and calcium-based antacids can increase stone risk.
• Family History: If someone in your family has had kidney stones, you're more likely to develop them.
• Supplements: High doses of Vitamin C and Vitamin D supplements can increase the risk of certain types of stones.

Symptoms

• Severe Pain in the Side and Back: Below the ribs (renal colic). This pain may radiate to the lower abdomen and groin.
• Pain That Comes in Waves: And fluctuates in intensity.
• Pain or Burning Sensation During Urination.
• Pink, Red, or Brown Urine: Due to blood in the urine (hematuria).
• Cloudy or Foul-Smelling Urine.
• Nausea and Vomiting.
• Persistent Need to Urinate.
• Urinating More Often Than Usual.
• Fever and Chills: If an infection is present.
• Small Amount of Urine: Or difficulty urinating.

Diagnosis

• Medical History and Physical Exam: The doctor will ask about your symptoms, diet, fluid intake, and any family history of kidney stones. A physical exam may reveal tenderness in the back or abdomen.
• Urine Tests:
  • Urinalysis: To check for blood, infection, and levels of stone-forming substances.
  • 24-hour urine collection: To measure the volume of urine and the levels of minerals and salts that form stones.
• Blood Tests: To check kidney function and levels of calcium, phosphorus, uric acid, and electrolytes.
• Imaging Tests:
  • X-ray (Kidneys, Ureters, and Bladder - KUB): Can detect some types of kidney stones.
  • CT Scan (Computed Tomography): Often the preferred imaging test for kidney stones, as it can detect even small stones and show their precise location.
  • Ultrasound: A non-invasive test that can identify kidney stones, especially in pregnant women or those who need to avoid radiation.
  • Intravenous Pyelogram (IVP): Involves injecting a dye into a vein and taking X-rays to visualize the urinary tract and identify obstructions. Less commonly used now with the advent of CT scans.
• Stone Analysis: If you pass a stone, it will be collected and analyzed to determine its composition. This helps in understanding the cause and guiding preventive measures.

Treatment

• Conservative Management (for small stones):
  • Drink Plenty of Water: 2 to 3 quarts (about 2 to 3 liters) of water a day to help flush out the stone.
  • Pain Relievers: Over-the-counter pain medications (e.g., ibuprofen, naproxen) or prescription pain relievers.
  • Alpha-Blockers: Medications like tamsulosin (Flomax) can relax the muscles in your ureter, making it easier for the stone to pass.
• Medical Procedures (for larger or problematic stones):
  • Extracorporeal Shock Wave Lithotripsy (ESWL): Uses sound waves to break the stones into tiny pieces that can then be passed in the urine.
  • Ureteroscopy: A thin, lighted scope (ureteroscope) is passed through the urethra and bladder into the ureter to locate and remove or break up the stone with a laser.
  • Percutaneous Nephrolithotomy (PCNL): For very large or complex stones. A small incision is made in the back or side, and a scope is inserted directly into the kidney to remove the stone.
  • Parathyroid Gland Surgery: If kidney stones are caused by an overactive parathyroid gland, surgical removal of the affected gland may be recommended.
• Dietary and Lifestyle Changes (for prevention):
  • Increase Fluid Intake: Especially water, to produce at least 2 liters of urine daily.
  • Reduce Sodium Intake: Avoid high-sodium processed foods.
  • Limit Animal Protein: Especially red meat.
  • Moderate Oxalate Intake: If you form calcium oxalate stones, your doctor may advise reducing high-oxalate foods.
  • Maintain a Healthy Weight.
• Medications (to prevent future stones, based on stone type):
  • Thiazide diuretics: For calcium stones.
  • Allopurinol: For uric acid stones.
  • Sodium bicarbonate or potassium citrate: To make urine less acidic.
  • D-penicillamine or tiopronin: For cystine stones.

Passing a Stone and Preventing the Next One

Roughly half of people who form one kidney stone form another within a decade, and most of that is preventable with changes more specific than "drink more water." Here is what to expect while a stone passes and what prevention adds.

What passing a stone at home looks like

Stones smaller than about five millimeters usually pass on their own within a few weeks, and the alpha-blocker tamsulosin speeds passage of stones in the lower ureter. Pain comes in waves as the stone moves; ibuprofen or naproxen controls it better than opioids, provided kidney function is normal. Urinate through a strainer until the stone is caught, because analyzing it decides the prevention plan.

When home management stops being safe

Fever or chills with a stone means an infection trapped behind a blockage, which can become life-threatening within hours and needs emergency drainage. Uncontrolled pain, vomiting that prevents keeping fluids down, a stone in someone with a single working kidney or chronic kidney disease, or a stone that has not passed in four to six weeks all need urology involvement.

Heat is why Florida forms more stones

Sweating concentrates urine, and outdoor work or exercise here in summer can push urine output well below the two liters a day or more that protects against stones. The test is urine color: pale yellow all day. Our kidney stone prevention in the St. Pete heat article and hydration guide give practical targets.

The calcium mistake

People with calcium stones often cut dairy, which backfires: dietary calcium binds oxalate in the gut so it never reaches the urine, and low-calcium diets raise stone risk and weaken bone. Keep normal calcium intake from food, take any supplement with a meal, and cut sodium instead, since salt drives calcium into the urine; lemon juice or a citrate supplement raises the citrate that keeps crystals from forming.

The workup after a second stone

Two stones, a stone in childhood, or a family history calls for a 24-hour urine collection, which shows whether the problem is low volume, high calcium, high oxalate, low citrate, or acid urine, and blood tests check for hyperparathyroidism and gout. Treatment follows the result: hydrochlorothiazide for high urine calcium, potassium citrate for low citrate or uric acid stones, allopurinol when uric acid is high. Obesity and diabetes acidify urine and favor uric acid stones, so weight and blood sugar are part of prevention. Our genito-urinary team runs the workup and coordinates with urology. NIDDK and the National Kidney Foundation publish patient guidance on prevention.

If you have passed more than one stone and never had a 24-hour urine test, schedule a visit; the next one is usually preventable.