Introduction & Objectives
To study the options offered by computed tomography (CT) scan in patients with urolithiasis to perform calculi measurements and body distances. To analyze the influence of these measures on the effectiveness of treatment with extracorporeal shockwave lithotripsy (ESWL).
Material & Methods
We analyzed 137 patients with previous CT scan between those treated by ESWL between 2007 and 2015. We measured several calculi and body radiological variables: maximum diameter in millimetres (mm), area in square millimetres (mm²), maximum stone density in Hounsfield Units (UH), skin-to-stone distance (SSD) in centimetres (cm) and adipose panicle thickness at umbilical level (cm). Using ROC curves we chose the best cut-off point and performed binary logistic regression (univariate study) to study the influence on the need of retreatment (IBM SPSS version 20.0).
The mean and extreme values of the variables studied in the 137 patients: diameter 9 mm (3-28.3), area 58.8 mm² (5-347.9), maximum density 844 UH (45-1693), SSD 11.3 cm (4.46-18.1) and adipose panicle thickness 2.57 cm (1-5.69). The area under the curve (AUC) of each variable: 0.628 (diameter), 0.666 (area), 0.692 (maximum density), 0.496 (SSD) and 0.547 (adipose panicle thickness). The best cut-off point for each variable was 9.5 mm (diameter), 55 mm² (area), 1000 HU (maximum density), 11.5 cm (SSD) and 2.7 cm (adipose panicle thickness). In the univariate study the influential variables were: diameter (OR: 2.12 CI95% 1.01-4.44, p = 0.046), area (OR: 3.53 CI95% 1.67-7.47, p = 0.001) and maximum stone density (OR: 2.72 CI 95% 1.29-5.75, p = 0.009). In the univariate study, there were not influential: SSD (OR: 1.08 CI 95% 0.53-2.22, p = 0.828) and adipose tissue thickness (OR: 1.19 CI 95% 0.58-2 , 43, p = 0.641).
CT scan provides prior information that can predict the effectiveness of the treatment with ESWL. Between the studied measures, only the diameter, area and maximum stone density were influential. Further studies are needed to evaluate the usefulness of body measurements such as skin-to-stone distance and adipose panicle thickness.