Analysis of urinary calculi composition by infrared spectroscopy: a prospective study of 625 patients in eastern China.

Urolithiasis is a common urologic disease whose prevalence is about 1-20% and increasing throughout the world. The recurrence rate after treatment is more than 50%. Urinary stone analysis is important in determining the possible etiology and the pathophysiology of stone formation. A better understanding of the stone composition may help prevent urinary stone formation. From March 2007 to December 2008, physical analysis of urolithiasis in patients who lived in eastern China for more than 5 years and underwent surgery or shock wave lithotripsy in our hospital or passed their stones spontaneously was carried out using the Fourier transform infrared spectroscopy (FT-IR). Clinical and demographic findings were evaluated and compared with the stone components. Stone analysis was performed in 625 patients. The FT-IR evaluation showed that 234 (37.4%) were pure, and the most frequent was calcium oxalate (33.9%), followed by calcium phosphate (2.7%), and uric acid (0.8%). 391 (62.6%) were mixed stone, calcium oxalate (43.2%) was the most commonly major component, followed by calcium phosphate (16.3%), cystine (1.3%), uric acid (1.1%), and struvite (0.6%). Uric acid (p = 0.029) was the major component found more frequently in men, while struvite (p = 0.037) was more frequent in women. Uric acid (p = 0.031) was more common in lower urinary tract stones, and its formers with the mean age of 55 years were older than those with other components (p = 0.039). In eastern China, the most commonly found pure stone was calcium oxalate, while the most frequent mixed stone was calcium oxalate and calcium phosphate mixture. Stone location, gender, and age may influence stone component.