Kidney stone

A kidney stone is a solid crystal mass that forms in the urinary tract when substances in urine crystallize. Its size and location influence whether it passes without treatment or obstructs urine flow.

Urinary supersaturation: A state in which urine contains more dissolved mineral than it can keep in solution. Supersaturation lets stone-forming substances leave solution and begin crystallizing.
Urinary system: The organs and structures that produce, store, and eliminate urine. Kidney stones form within this system and may obstruct its passages.
Noncontrast CT: Computed tomography performed without injected contrast material. It can locate most urinary stones and estimate their size and obstruction.
Uric acid stone: A urinary stone composed primarily of uric acid or urate salts. Unlike common calcium oxalate stones, it is strongly associated with acidic urine.
Hydronephrosis: Swelling of a kidney caused by urine buildup behind an obstruction. A stone blocking urine drainage can produce this pressure-related kidney change.
Nucleation: The initial formation of a stable cluster of molecules or ions from a solution. It is one route by which the first crystals of a stone can form.
Nephron: The microscopic functional unit of a kidney that filters blood and modifies fluid into urine. Its work determines much of the water and solute composition from which stones form.
Urinalysis: Laboratory examination of urine for cells, chemicals, and other abnormalities. It can reveal blood, infection, or chemical clues in a stone episode.
Struvite stone: A urinary stone composed of magnesium ammonium phosphate, often associated with urease-producing bacteria. Its infection-related formation differs from stones driven mainly by urine chemistry.
Hematuria: The presence of red blood cells in urine, visible or detectable only by testing. A moving stone can irritate or injure the urinary tract lining.

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