Table 1.
Summary of study results.
| US group (n = 57) |
FS group (n = 57) |
Statistical analysis | |
|---|---|---|---|
| Factors influencing SWL outcome | |||
|
| |||
| Stone-related factors | |||
| Stone size | |||
| Mean stone size (mm)(1) | 9 (σ = 3) | 8.5 (σ = 3) | p = 0.29 |
| Number of stones 0–4 mm | 5 | 5 | p = 1 |
| Number of stones 5–9 mm | 30 | 30 | p = 1 |
| Number of stones 10–20 mm | 22 | 22 | p = 1 |
| Stone composition (2) | |||
| Number of hard stones(3) | 6 (n = 30) | 4 (n = 25) | p = 0.50 |
| Stone position | |||
| Number of lower pole stones | 22 (39%) | 22 (39%) | p = 1 |
| Number of pyelum and PUJ stones | 5 (9%) | 8 (14%) | p = 0.37 |
| Number of upper pole stones | 18 (31%) | 8 (14%) | p = 0.02 |
| Number of midpolar stones | 12 (21%) | 19 (33%) | p = 0.14 |
| Stone density (HU) (4) | |||
| Mean stone density (HU) | 665 (σ = 160, n = 31) | 740 (σ = 223, n = 29) | p = 0.10 |
| Maximal stone density (HU) | 965 | 1213 | NA |
|
| |||
| Operator-related factors | |||
| Experience with both techniques | 2 investigators with equal experience | NA | |
|
| |||
| Patient-related factors | |||
| Mean BMI (kg/m2) | 27 (σ = 3,8) | 29 (σ = 3,3) | p = 0.001 |
| Mean skin-to-stone distance (mm)(5) | 90 (σ = 13, n =31) | 104 (σ = 14, n = 29) | p < 0.001 |
|
| |||
| Technique-related factors | |||
| Shock frequency (bpm) | 60 | p = 1 | |
| Number of shocks | 2500 | p = 1 | |
| Ramping protocol | Identical in both groups | NA | |
| Mean energy (Joule) | 49 (σ = 11) | 53 (σ = 11) | p = 0.002 |
|
| |||
| Study outcomes | |||
|
| |||
| Clinical outcome | |||
| Number of stone-free patients | 30 | 24 | Noninferior(6) |
| Number of patients with asymptomatic residual fragments | 15 | 16 | |
| Number of patients with a positive outcome(7) | 45 | 40 | Noninferior(6) |
| Number of patients needing additional therapy | 6 | 9 | |
| Number of patients with no effect | 6 | 8 | |
| Number of patients with a negative outcome(8) | 12 | 17 | Noninferior(6) |
|
| |||
| Number of ESWL sessions | |||
| Mean number of SWL sessions/patient | 1.6 (σ = 0,7) | 1.7 (σ = 0,7) | p = 0.431 |
|
| |||
| Positioning | |||
| Mean number of position changes/patient | 8 (σ = 2) | 6 (σ = 2) | p = 0.008 |
| Mean time to position/patient | 9 (σ = 2) | 5 (σ = 2) | p < 0.001 |
|
| |||
| Radiation | |||
| Mean DAP (mGy/cm2)/SWL session | 0 | 3005 (σ = 601) | p < 0.001 |
(1) Measured as longest stone distance on RX before the first SWL session. (2) Only 55/114 (48%) patients analysed their stone. (3) Calcium oxalate monohydrate (whewellite), cystine, or calcium phosphate (brushite) stones. (4) Hounsfield units as measured on CT abdomen. (5) Measured vertically in the US group and 45° in the FS group. (6) With a noninferiority margin of 10%. (7) Stone-free or asymptomatic residual fragments ≤ 4 mm. (8) Additional therapy or no effect.