Once it has been documented that a patient has symptomatic nephrolithiasis, determining the type of stone and the possible presence of either biochemical abnormalities or underlying conditions that predispose to stone formation are essential for guiding therapy to prevent recurrent disease.
TYPE OF STONE
Patients should be encouraged to retrieve stones they pass or have removed for analysis, although novel computerized tomography (CT) imaging techniques may permit noninvasive discrimination among the main subtypes of urinary calculi. (See "Diagnosis and acute management of suspected nephrolithiasis in adults", section on 'Determination of stone composition'.) Analysis of the stone is an essential part of the evaluation [1,2]. (See "Interpretation of kidney stone analysis".)
Approximately 80 percent of patients with urolithiasis form calcium stones, most of which are composed primarily of calcium oxalate or, less often, calcium phosphate [3-6]. The other main types include uric acid, struvite (magnesium ammonium phosphate), and cystine stones. The same patient may have a mixed stone (eg, calcium oxalate and uric acid).
Calcium stones — Stones composed purely or predominantly of calcium oxalate can occur in various disorders. In general, calcium phosphate stones are associated with the same risk factors as calcium oxalate stones (other than hyperoxaluria) . (See "Risk factors for calcium stones in adults".)
Biochemical risk factors — A number of biochemical urinary risk factors are associated with calcium stone formation [3,5,8]: