Calcium Phosphate Stone Morphology: Plain Radiographic Findings and Interobserver Variabilities

In current study, visual appearance of pure calcium phosphate (CaP) urinary stones by its morphology from plain radiograph (KUB), were investigated. We reviewed patients with urinary stone disease who underwent stone surgery. Among cases with crystallographically analyzed stones; 60 patients with pure CaP renal or ureteral stones (greater than 1 cm) were selected. Two endourologists and a uroradiologist familiar with the radiographic patterns of different types of pure stones were invited separately, to evaluate pretreatment KUB. Four different radiographic patterns were identified mainly with the assistance of previous studies. Smooth edged, homogenous stones with denser opacity were included in Group 1. Stones with irregular edges and stippled border were included in Group 2. Relatively uniform stones with radial striations and moderate density were decided to form Group 3. Calculi with the least radiodensity and loosely aggregated with a lacy structure were included in Group 4. Overall, 68.9% of CaP calculi were included in Groups 1 and 2 by all participants. Best concordance between endourologists and the uroradiologist was demonstrated in the evaluation of smaller calculi (< 150 mm2). On KUB, CaP urinary calculi were mostly seen as dense relatively homogenous stones and sometimes with stippled borders. With an increase in pretreatment stone size, interobserver and interdisciplinary variabilities increased.