IDENTIFYING CALCIUM-OXALATE CRYSTALS IN URINE

Proper identification of urine crystals is essential in the routine mi croscopic examination of urine sediment. Knowledge of structure, solub ility, and pH characteristics of urine crystals comes with training an d experience. References are available that provide excellent photogra phs and illustrations to assist with recognition. In addition, these r eferences provide guidelines far specialized testing or polarization c haracteristics of specific urine crystals to further assist in identif ication. Although crystals most often seen in urine generally are unre lated to pathology and are considered Normal, they must be properly id entified and reported because, occasionally they may have clinical sig nificance. For example, calcium oxalate has been considered one of the normal crystals, but it has been linked to lithiasis. This is the sec ond article in a three-part continuing education update series on urin alysis. Other articles in the series focus on urine sediment diagnosis and urine cytodiagnostics.