Pathophysiology and management of calcium stones

Nephrolithiasis is a common disorder that accounts for significant cost, morbidity, and loss of work. In the United States., the estimated annual expenditure for the diagnosis and treatment of nephrolithiasis approached $2.1 billion in 2000, almost certainly an underestimate, without taking into account lost wages and reduced work productivity [1]. Indeed, there is a one in eight lifetime chance of being diagnosed with urinary stones [2-4]. Although in most cases stones are source of discomfort and inconvenience without significant risk to health, progressive loss of renal function can occur after repeated episodes of stone disease. In a French study of over 1300 patients newly requiring hemodialysis, 3.2% of cases were directly related to stone disease [5]. With comprehensive evaluation, metabolic abnormalities can be identified in over 90% of stone formers. and the institution of preventive dietary and medical measures has resulted in substantial reduction in stone recurrence rates [6,7]. A careful medical and dietary history, serologic tests, and Urinalysis constitute the initial screening tools in stone formers. Stone analysis by radiographic crystallography or infrared spectrophotometry is an important component of this initial evaluation, because comprehensive metabolic testing may be foregone in lieu of more directed evaluation in patients who have non-calcium-containing stones such as uric acid and cystine, in whom the underlying pathophysiologic abnormalities are implied by the stone composition [8]. In contrast. stones (calcium oxalate [CaOx] and calcium phosphate) form as a result of a variety of environmental risk factors and metabolic derangements, and identification of these factors composes the mainstay of the evaluation and treatment plan for these patients. Among the various stone compositions, calcium-containing stones represent approximately 75% to 80% of upper tract stones. The remaining 20% to 25% are composed of struvite, cystine, uric acid, and other stones [9]. In this article, the authors review our current understanding of the pathophysiology of calcium stone disease, and propose contemporary medical and dietary prophylactic regimens.