Epidemiology and Incidence of Stone Disease

Abstract

Urinary stones are polycrystalline aggregates consisting of varying amounts of crystal and organic matrix components. Although urolithiasis is inclusive of renal, ureteral, and bladder stones, the following discussion will pertain only to symptomatic renal and ureteral stones, as they are the most common. The most common urinary stone types are calcium oxalate, calcium phosphate, uric acid, struvite (magnesium ammonium phosphate), and cystine. In an analysis of 14,557 renal and ureteral stones, 52% were purely calcium oxalate, 13% purely calcium phosphate, 15% a mixture of calcium oxalate and phosphate, 4% struvite, 8% uric acid, and 8% other compounds (1). As the majority of stones are of the calcium variety, it is likely that most epidemiological studies of nephrolithiasis pertain to this compositional form. Of the less common stone varieties, struvite stones are commonly associated with urinary tract infections, most notably secondary to urease splitting organisms such as Proteus and Klebsiella. Uric acid stones, associated with hyperuricosuric patients, are found in patients with gout, dehydration, and excessive purine intake. Finally, cystine stones are a rare form associated with inborn errors of metabolism resulting in abnormal absorption of dibasic amino acids in the small bowel and proximal renal tubule.