Kidney Stones
Hard deposits of minerals and salts that form in the kidneys and cause excruciating pain when they travel down the urinary tract.
Emergency Management: Obstructive pyelonephritis (stone + fever) is a surgical emergency requiring immediate decompression of the kidney via a percutaneous nephrostomy tube or retrograde ureteral stent, along with broad-spectrum IV antibiotics.
Nephrolithiasis is a condition characterized by the formation of solid, crystalline mineral deposits (stones) within the kidneys, which can cause severe pain and obstruction when they migrate into the ureters.
Detailed Overview
Stones form when the urine becomes supersaturated with stone-forming salts (calcium, oxalate, uric acid) and lacks adequate inhibitors (citrate, fluid volume). The vast majority are calcium oxalate stones. They represent a major source of acute, severe emergency department visits and can lead to recurrent infections or chronic kidney disease if obstructive.
Epidemiology & Demographics
Lifetime prevalence is around 10% in the United States. They are more common in men (approx 12%) than women (approx 7%), with peak incidence between 30 and 50 years of age. Recurrence rates are up to 50% within 10 years if untreated.
Etiological Mechanism
Multifactorial, involving low fluid intake, dietary indiscretion (high sodium, high animal protein), metabolic derangements (hypercalciuria, hypocitraturia), and anatomical anomalies.
Primary Causes
Dehydration (low urine volume)
Hypercalciuria (idiopathic or secondary to hyperparathyroidism)
Hyperuricosuria (gout, high purine diet)
Infection (Proteus or Klebsiella splitting urea to form struvite stones)
Stones form through nucleation, growth, and aggregation of crystals in supersaturated urine. Calcium oxalate (80%) forms over a nidus of calcium phosphate (Randall's plaque) in the renal papillae. Uric acid stones (10%) form in highly acidic urine (pH < 5.5). Struvite stones (magnesium ammonium phosphate) form rapidly in alkaline urine caused by urease-producing bacterial infections, often growing to form massive 'staghorn' calculi filling the renal pelvis.
Diagnostic Criteria & Guidelines
Classic clinical presentation combined with imaging demonstrating a radiopaque or radiolucent stone in the urinary tract, often with associated proximal hydronephrosis.
For stones < 5mm (usually pass spontaneously): 1. Analgesia: NSAIDs (Ketorolac 15-30 mg IV or Ibuprofen 600 mg PO) are superior to opioids because they decrease ureteral smooth muscle tone. 2. Medical Expulsive Therapy (MET): Tamsulosin 0.4 mg PO daily to relax distal ureter. 3. Hydration and antiemetics (Ondansetron).
Second-Line & Adjunctive Therapy
For Uric Acid Stones: Urinary alkalinization with Potassium Citrate (aiming for urine pH 6.5-7.0) can actually dissolve uric acid stones. For recurrent calcium stones: Thiazide diuretics (Chlorthalidone) to reduce urine calcium.
Surgical & Procedural Management
For stones > 10mm, failing to pass, or causing severe pain/AKI: 1. Ureteroscopy (URS) with laser lithotripsy and stent placement. 2. Extracorporeal Shock Wave Lithotripsy (ESWL) for smaller upper tract stones. 3. Percutaneous Nephrolithotomy (PCNL) for large (>2cm) or staghorn stones.
Patient Counseling & Advice
Use a urine strainer at home to catch the stone for laboratory analysis, which dictates the specific dietary and medical prevention strategy.
Follow-Up & Monitoring Schedule
Outpatient urology follow-up with KUB X-ray or ultrasound in 2-4 weeks to confirm stone passage if asymptomatic. Metabolic evaluation (24-hour urine) for recurrent stone formers.
Preventive Strategies
Thiazide diuretics for hypercalciuria. Allopurinol for hyperuricosuria. Potassium citrate for hypocitraturia. High fluid intake for all.
Most small stones pass within 2-4 weeks. Without metabolic management and lifestyle changes, 50% of patients will have another stone within 5-10 years.