Introduction
Kidney stones refer to solid crystalline aggregates formed from supersaturated solutes in the urinary tract.
These calculi may be asymptomatic or present with acute symptoms upon migration or obstruction.
A rising incidence is noted globally, with a lifetime prevalence of 10–15% and recurrence rates reaching 50% within 5–10 years.
Etiology and Risk Factors
Metabolic Abnormalities
Hypercalciuria, hyperoxaluria, hyperuricosuria, and hypocitraturia significantly contribute to lithogenesis.
Hypocitraturia reduces urinary citrate, a natural inhibitor of calcium crystallization.
Dietary and Fluid Intake Factors
High dietary sodium, animal protein, fructose, and oxalate-rich foods (e.g., spinach, chocolate, nuts).
Low fluid intake leads to concentrated urine and supersaturation of stone-forming salts.
Genetic and Systemic Conditions
Genetic predispositions, such as cystinuria, Dent's disease, and primary hyperoxaluria.
Comorbidities: Obesity, metabolic syndrome, type 2 diabetes, and inflammatory bowel disease.
Occupational and Environmental Exposure
Heat-exposed or dehydrated occupational settings (e.g., industrial workers and surgeons) increase the risk of stone formation.
Stone Classification
Calcium Oxalate Stones (≈50%)
Formed due to hypercalciuria, often exacerbated by low urinary citrate and high oxalate intake.
Randall's plaques serve as nucleation sites.
Mixed Calcium Phosphate and Oxalate Stones (≈45%)
Favored by alkaline urine and may coexist with calcium oxalate.
Uric Acid Stones (≈9%)
Form in persistently acidic urine and are linked to high purine intake and gout.
Struvite Stones (≈10%)
Associated with urea-splitting organisms (e.g., Proteus, Klebsiella), leading to staghorn calculi.
Cystine Stones (≈1%)
Result from inherited cystinuria; typically present in youth with recurrent, bilateral stones.
Clinical Presentation
Renal colic: sudden, severe flank or abdominal pain radiating to the groin.
Hematuria: visible or microscopic blood in urine.
Associated symptoms: nausea, vomiting, dysuria, urgency, and frequency.
Recurrent urinary tract infections may be a sign of infected or obstructing calculi.
Diagnostic Evaluation
Clinical Assessment
Detailed dietary, medical, and family history.
Pain characteristics and prior stone episodes were evaluated.
Laboratory Workup
Urinalysis: hematuria, pyuria, crystals, pH abnormalities.
Serum: calcium, uric acid, creatinine.
24-hour urine: evaluates excretion of calcium, oxalate, uric acid, and citrate.
Imaging Modalities
Non-contrast CT scan (NCCT): gold standard for diagnosis and stone localization.
Ultrasound: preferred in children and pregnant women.
KUB X-ray: useful in monitoring radiopaque stones.
Management Strategies
Lifestyle and Dietary Modification
High fluid intake to maintain urine volume >2.5 L/day.
The DASH-style diet reduces stone recurrence by enhancing citrate levels and reducing sodium and oxalate intake.
Limit oxalate (e.g., rhubarb, beetroot), sodium, animal proteins, and added sugars.
Pharmacologic Interventions
Thiazide diuretics: reduce urinary calcium; however, the NOSTONE trial showed limited efficacy and increased metabolic side effects (e.g., gout, diabetes).
Potassium citrate: alkalinizes urine and increases urinary citrate; used for uric acid and cystine stones.
Allopurinol: indicated in hyperuricosuric patients with uric acid or calcium stones.
Tiopronin or penicillamine: for cystinuria when hydration and alkalinization are inadequate.
Surgical and Minimally Invasive Therapies
ESWL (Extracorporeal Shock Wave Lithotripsy): non-invasive, suitable for stones <2 cm in the renal pelvis.
Ureteroscopy (URS): preferred for ureteric stones; allows direct visualization and laser fragmentation.
PCNL (Percutaneous Nephrolithotomy): indicated for large (>2 cm), complex, or staghorn stones.
Open/laparoscopic stone surgery: rare, used in refractory or anatomically challenging cases.
Recurrence Prevention and Follow-Up
Individualized metabolic evaluation after the first episode, especially in recurrent formers.
Long-term dietary counseling based on 24-hour urine parameters.
Monitoring includes annual imaging, renal function assessments, and metabolic reassessments.
A multidisciplinary approach involving urologists, nephrologists, and dietitians improves outcomes.
Conclusion
Kidney stone disease represents a significant global health burden with high recurrence potential and complex metabolic underpinnings.
Contemporary management integrates precision diagnostics, tailored dietary and pharmacological strategies, and advanced minimally invasive interventions.
Future directions point toward personalized metabolic profiling and novel therapeutics to prevent recurrence and preserve renal function.