Nephrolithiasis (urolithiasis) is the formation of urinary calculi when urinary solutes — such as calcium, uric acid, and oxalate — become supersaturated in the urine, either from elevated solute concentration, reduced levels of stone-forming inhibitors (citrate, magnesium), low urine volume, or abnormal urinary pH, causing crystals to precipitate and grow within the nephron tubules or urinary tract. This is a core mechanism in renal pathology and urology, linking disturbances in electrolyte and fluid homeostasis to obstructive and inflammatory disease of the urinary system. Stones are classified histologically into calcium oxalate, calcium phosphate, struvite, uric acid, and cysteine types, each reflecting a distinct underlying metabolic or infectious cause.
Nephrolithiasis (urolithiasis) is the formation of urinary calculi when urinary solutes — such as calcium, uric acid, and oxalate — become supersaturated in the urine, either from elevated solute con…