175843.fig.001
Figure 1: Spectrophotometric crystallization curve:   start of increase of optical density (OD) reflecting crystal concentration in urine, (2) maximal OD (mOD) reached at the end of oxalate titration, (2)-(3) slow OD decrease ( ) by sedimentation of single crystals, and (3) start of rapid OD decrease ( ) indicating crystal aggregation.