Role of variation coefficient of stone density in determining success of shock wave lithotripsy in urinary calculi

Table 1 Demographic features of patients and stones

Demographic parameter	Result
Age (years)	38.89 ± 14.61
Gender, n (%)
Male	294 (72.2)
Female	113 (27.8)
Stone volume	223.34 ± 77.01
SSD (cm)1	9.52 ± 2.47
Stone density (HUs)	900 (110-1570)
SHI (HUs)2	174.85 (17.7-583.9)
VCSD3	22 (3-83)
Stone laterality, n (%)
Left sided	213 (52.3)
Right sided	194 (47.7)
Location stone, n (%)
Renal	316 (77.64)
Ureter	91 (22.36)

¹Skin-stone distance.

²Stone heterogeneity index.

³Variation coefficient of stone density.

SSD: Skin-stone distance; HUs: Hounsfield units; VCSD: Variation coefficient of stone density.

Table 2 Characteristics of patients and stones in stone free and failure groups

Parameter	Unsuccessful group	Successful group	P value
Age (years)1	38.82 ± 13.84	38.94 ± 15.13	0.93
Gender, n (%)			0.78
Male	118	176
Female	47	66
Stone volume2	240 (80-439)	200 (36-400)	< 0.0001
SSD (cm)1	9.63 ± 2.32	9.45 ± 2.56	0.47
Stone density (HUs)2	1217.30 (318-2000)	720.00 (110-1800)	0.0001
SHI (HUs)2	172.95 (22.7-571.4)	190.15 (17.7-583.9)	< 0.0001
VCSD2	15 (2-92)	28 (4-83)	< 0.0001
Stone laterality, n (%))			0.19
Left sided	80	133
Right sided	85	109
Stone location			0.69
Upper pole	12	17
Mid pole	29	38
Lower pole	46	79
Pelvis	39	55
Ureter	39	53

¹Continuous variables shown in mean (standard deviation).

²Continuous variables shown in median (quartile).

SHI: Stone heterogeneity index; HUs: Hounsfield units; VCSD: Variation coefficient of stone density; SSD: Skin-stone distance.

Table 3 Univariate and multivariate logistic regression analyses for significant factors regarding shock wave lithotripsy (one-session success)

Variable	Univariate			Multivariate
	OR	95%CI	P value	OR	95%CI	P value
Mean stone density	1.003	1.003-1.004	< 0.0001	1.003	0.424-1.346	< 0.0001
Standard deviation of stone density	0.996	0.995-0.998	< 0.0001	0.997	0.993-1.001	0.13
VCSD (%)1	0.895	0.874-0.917	< 0.0001	0.929	0.894-0.964	< 0.0001
Stone volume (mm3)	1.009	1.007-1.012	< 0.0001	1.005	1.002-1.009	< 0.005
Age (year)	0.99	0.985-1.012	0.86
Skin-stone distance	1.02	0.947-1.112	0.52
Gender (male)	0.949	0.611-1.475	0.81

¹Variation coefficient of stone density.

VCSD: Variation coefficient of stone density.