顯微鏡檢晨尿有尿酸結晶可預測腎臟尿酸結石的形成

盧艷金^1,3、曾一修^1,2

亞東紀念醫院 外科部 ¹創傷科，²泌尿科; ³醫學研究部

Positive microscopic uric acid crystal in the morning urine indicates renal uric acid stone formation

Yen-Chin Lu^1,3, Yi-Shiou Tseng^1,2

Divisions of Traumatology¹ and Urology², Department of Surgery, Far Eastern Memorial Hospital, New Taipei City, Taiwan

Department of Medical Research³, Far Eastern Memorial Hospital, New Taipei City, Taiwan

Purpose: Crystalluria analysis under microscope is a low-cost visual tool and one of the reliable methods to predict renal stone formation. Calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate, and uric acid are the major components of urinary crystals. The crystalline composition provides valuable information in the stone process. Our study aims to investigate whether microscopy for morning urine is a reliable method to predict renal uric acid stone formation.

Materials and Methods: 10 μL morning urine were obtained from 141 stone formers. 60 μL morning urine were obtained from 130 stone formers. 60 μL urine from 24-hour urine were obtained from 74 stone formers. Renal stones composition had been identified in all stone formers by ureteroscopy. Urine samples from stone formers were kept at room temperature and sent to the laboratory within 2 hours. The urine crystal types were examined at 200X magnification under microscopy. We compared the correlation between urine uric acid crystal and renal uric acid stones. Statistical analysis includes positive predictive value, negative predictive value, sensitivity, specificity, and Youdens index.

Results: Sensitivity is 0.57 and specificity is 1.00 from 10 μL morning urine. The positive predictive value is 1.00 and the negative predictive value is 0.98. The Youdens index is 57.14. On the other hand, from 60 μL morning urine sensitivity is 0.57 and specificity is 0.98. The positive predictive value is 0.67, the negative predictive value is 0.9758, and the Youdens index is 55.51. We also analyzed the results from 24-hour urine which reported that sensitivity is 0.60, specificity is 0.94, the positive predictive value is 0.43, the negative predictive value is 0.97, and the Youdens index is 54.02.

Conclusions: According to our findings, microscopic crystal examination for the morning urine is a reliable method to predict renal uric acid stone formation. We can provide medications for this kind of patients earlier who get benefit from stone prevention.