Urolithiasis

Definition

Urolithiasis refers to the formation of calculi (stones) anywhere in the urinary tract, including the kidneys, ureters, bladder, and urethra, often leading to pain, obstruction, and potential urinary tract infection.

Epidemiology

• Affects 5–10% of the population worldwide
• More common in men than women (3:1 ratio)
• Peak incidence between 30–50 years of age
• Higher prevalence in regions with hot climates and dehydration risk
• Recurrence rate is high, approximately 50% within 5–10 years
• Family history is a significant risk factor
• Associated with metabolic disorders such as hypercalciuria, hyperoxaluria, and gout

Etiology

• Supersaturation of urine with stone-forming salts: calcium oxalate, calcium phosphate, uric acid, cystine, struvite
• Metabolic disorders: hyperparathyroidism, renal tubular acidosis, gout
• Dietary factors: high salt, high protein, low fluid intake
• Genetic predisposition
• Urinary tract infections (especially struvite stones in Proteus infection)
• Anatomical abnormalities causing urinary stasis
• Medications such as loop diuretics or topiramate

Pathophysiology

• Nucleation of crystals in supersaturated urine
• Aggregation and growth of crystals into stones
• Deposition in renal calyces, renal pelvis, ureters, or bladder
• Obstruction of urinary flow leading to hydronephrosis
• Local inflammation and pain due to ureteral spasm
• Risk of secondary infection in obstructed or retained stones
• Chronic obstruction may cause renal parenchymal damage