Determination of urinary stone composition based on stone morphology: a prospective study of 325 consecutive patients in an emerging country

BACKGROUND: Urolithiasis is a common disease that is increasing throughout the world. This study aimed at determining the composition of urinary stones in patients with renal lithiasis in an emerging country. METHODS: A morphological analysis was performed on 340 urinary stones from 325 consecutive patients from Brazil with lithiasis. RESULTS AND CONCLUSIONS: Among the 340 stones analyzed, 34.7% were pure. The most frequent stone was calcium oxalate (CaOx) (59.3%), followed by uric acid (23.7%). CaOx was more frequently seen in women (p=0.024), while uric acid was more common in men (p<0.001). Among the mixed stones, CaOx (67.1%) was the most frequent major component, followed by carbapatite (11.2%) and struvite (7.9%). CaOx (p<0.001) and uric acid (p=0.014) were more frequently the major components in men, while carbapatite (p<0.001) and struvite (p=0.011) were more frequent in women. The major component of both pure and mixed stones was CaOx (65.1%), followed by uric acid (10.9%), carbapatite (10%), struvite (6.7%), ammonium urate (5.1%), cystine (1.8%) and protein (0.4%). These findings may be related to regional factors, such as weather and nutritional habits.