Table 2.
Univariate analysis of the pre-treatment factors, number of SWL sessions and follow-up imaging modality.
| Completely Stone Free Yes/No | Stone Free with CIRFs Yes/No | |||||||
|---|---|---|---|---|---|---|---|---|
| Yes | No | OR (95% CI) | p value | Yes | No | OR (95% CI) | p value | |
| No. treated cases | 213/459 (46.4) | 246/459 (53.6) | — | — | 282/459 (61.4) | 177/459 (38.6) | — | — |
| Gender: | ||||||||
| Male | 129/300 (43) | 171/300 (57) | 1 | — | 177/300 (59) | 123/300 (41) | 1 | — |
| Female | 84/159 (52.8) | 75/159 (47.2) | 1.49 (1.01, 2.29) | 0.049 | 105/159 (66) | 54/159 (34) | 1.35 (0.91, 2.02) | 0.159 |
| Patient age (yrs) | 51.0 (40–64) | 57 (47–67) | — | 0.0016 | 52.0 (41–65) | 57.0 (48–67) | — | 0.0026 |
| Side of stone: | ||||||||
| Left | 118/254 (46.5) | 136/254 (53.5) | 1 | — | 159/254 (62.6) | 95/254 (27.4) | 1 | — |
| Right | 95/205 (46.3) | 110/205 (53.7) | 1.00 (0.69, 1.44) | 1.000 | 123/205 (60) | 82/205 (40) | 0.89 (0.61, 1.31) | 0.630 |
| SSD; mm* | 109 (88–124) | 102 (83–121) | — | 0.0931 | 105 (86–120) | 108 (84–125) | — | 0.4843 |
| Renal vs. Ureteric stones: | ||||||||
| Kidney (all sites) | 137/338 (40.5) | 201/338 (59.5) | 1 | — | 199/338 (58.9) | 139/338 (41.1) | 1 | — |
| Ureter | 76/121 (62.8) | 45/121 (37.2) | 2.48 (1.62, 3.80) | <0.001 | 83/121 (68.6) | 45/121 (31.4) | 1.53 (0.98, 2.37) | 0.065 |
| No. stone location (%) compared to Ureteric Stones as the reference category: | ||||||||
| Upper and Midpole | 44/117 (37.6) | 73/117 (62.4) | 0.36 (0.21, 0.60) | <0.001 | 72/117 (61.5) | 45/117 (38.5) | 0.73 (0.43, 1.25) | 0.278 |
| Lower pole | 63/161 (39.1) | 98/161 (60.9) | 0.38 (0.23, 0.62) | <0.001 | 91/161 (56.5) | 70/161 (43.5) | 0.60 (0.36, 0.98) | 0.048 |
| Renal pelvis/PUJ | 30/60 (50) | 30/60 (50) | 0.59 (0.32, 1.11) | 0.111 | 36/60 (60) | 24/60 (40) | 0.69 (0.36, 1.31) | 0.318 |
| Ureteric stent present: | ||||||||
| No | 197/427 (46.1) | 230/427 (53.9) | 1 | — | 263/427 (61.6) | 164/427 (38.4) | 1 | — |
| Yes | 16/32 (50) | 16/32 (50) | 1.17 (0.57, 2.40) | 0.716 | 19/32 (59) | 13/32 (41) | 0.911 (0.44, 1.89) | 0.852 |
| Measures of stone burden: | ||||||||
| 1 Stone | 204/397 (51.4) | 193/397 (48.6) | 1 | — | 255/397 (64) | 142/397 (36) | 1 | — |
| 2 Stones | 6/40 (15) | 34/40 (85) | 0.17 (0.07, 0.41) | <0.001 | 19/40 (48) | 21/40 (52) | 0.50 (0.26, 0.97) | 0.041 |
| Major axis length; mm* | 6.7 (5.3–8.7) | 7.7 (6.1–10.8) | — | <0.0001 | 6.7 (5.3–8.7) | 8.3 (6.3–11.4) | — | <0.0001 |
| Minor axis length; mm* | 4.7 (3.8–6.1) | 5.4 (4.2–7.2) | — | 0.0001 | 4.7 (3.7–6.1) | 5.8 (4.4–7.7) | — | <0.0001 |
| Vertical axis length; mm* | 6.9 (5.0–9.2) | 7.4 (5.5–10.3) | — | 0.0176 | 6.7 (4.8–9.0) | 8.0 (6.0–11.1) | — | <0.0001 |
| Volume(s); mm3† | 109 (53–231) | 156 (76–403) | — | <0.0001 | 102 (51–241) | 201 (95–522) | — | <0.0001 |
| Total no. pixels* | 62 (37–101) | 82 (49–140) | — | <0.0001 | 62 (37–101) | 88 (53–153) | — | <0.0001 |
| Measures of stone density and heterogeneity (CTTA variables): | ||||||||
| Mean HU* | 543 (252–440) | 587 (455–726) | — | 0.0201 | 532 (413–664) | 605 (481–759) | — | 0.0001 |
| SD of the HU* | 364 (253–440) | 385 (300–458) | — | 0.0799 | 362 (250–440) | 391 (316–464) | — | 0.0129 |
| MPP* | 545 (416–680) | 589 (461–732) | — | 0.0202 | 535 (415–668) | 610 (489–761) | — | 0.0001 |
| Entropy* | 4.1 (3.6–4.6) | 4.3 (3.8–4.8) | — | <0.0001 | 4.1 (3.6–4.6) | 4.5 (3.9–4.9) | — | <0.0001 |
| Kurtosis* | −1.11 (−1.29– −0.89) | −1.11 (−1.30– −0.82) | — | 0.8733 | −1.09 (−1.25– −0.87) | −1.14 (−1.33– −0.82) | — | 0.1497 |
| Skewness* | 0.35 (0.08–0.52) | 0.28 (−0.11–0.54) | — | 0.0501 | 0.37 (−0.10–0.54) | 0.20 (−0.16–0.51) | — | 0.0002 |
| No. SWL sessions‡ | 1.0 (1–2) | 2.0 (1–4) | — | <0.0001 | 1.0 (1–2) | 2.0 (2–4) | — | <0.0001 |
| No. follow-up imaging modality: | ||||||||
| X-ray | 136/286 (47.6) | 150/286 (52.4) | 1 | — | 177/286 (61.9) | 109/286 (28.1) | 1 | — |
| US | 23/43 (53) | 20/43 (47) | 1.27 (0.66, 2.41) | 0.515 | 30/43 (70) | 13/43 (30) | 1.42 (0.71, 2.84) | 0.398 |
| CT KUB | 53/127 (42) | 74/127 (58) | 0.79 (0.52–1.20) | 0.286 | 72/127 (56.7) | 55/127 (43.3) | 0.81 (0.53–1.23) | 0.329 |
Values are median (IQR) or number (%). Continuous variables underwent the Mann–Whitney U test and therefore only the p-value is presented. Categorical variables underwent the chi-square test with odds ratios expressed relative to the reference group (usually chosen as group with the largest number of cases), with asymptotic confidence intervals and Fisher’s exact p values. Odds ratios and p-values have not been included for groups with less than 3 observations, when split by outcome. * Values were measured from the largest cross-sectional slice of the largest stone in cases where more than one stone was treated. † Stone volume is the sum of individual stone volumes in cases with more than one stone. CIRFs, clinically insignificant residual fragments; CT KUB, computed tomography kidneys ureter bladder; CTTA, computed tomography texture analysis; HU, Hounsfield unit; PUJ, pelviureteric junction; SD standard deviation; SSD, skin-to-stone distance; SWL, extracorporeal shockwave lithotripsy; US, ultrasound scan, VUJ, vesicoureteric junction.