Table 1. Favourable technical factors for shock wave lithotripsy.
| Factor | Evidence | Study type | Level of evidence | GRADE rating | Reference |
|---|---|---|---|---|---|
| Shock wave generation | No difference between lithotripter type (electrohydraulic, electromagnetic or piezoelectric) | Cohort study | 2b | Moderate | (3-5) |
| Patient position | Patients with distal ureteric stones may be appropriately managed with SWL in the supine position | Meta-analysis | 1a | High | (6) |
| PDI therapy is safe and may improve passage of lower pole renal stones | Meta-analysis | 1a | Moderate | (7) | |
| SWL in the inclined position is safe and may increase stone passage in lower pole renal stones | Randomised controlled trial | 1b | Moderate | (8,9) | |
| Number of shocks | No trials investigating optimal number of shocks per session | – | – | – | – |
| Rate | Low (60 SPM) and Intermediate (80–90 SPM) rate SWL has higher success rates than high (120 SPM) rate SWL. Low rate SWL has the lowest complication rates | Meta-analysis | 1a | High | (10) |
| Energy | Energy ramping techniques reduce renal injury during SWL | Randomised controlled trial | 1b | High | (11) |
| Coupling | Defects (air pockets) in lithotripter-patient coupling can reduce shock wave amplitude by a mean 20% | In vitro study | – | High | (12) |
| Water soluble lubricating jelly is a good coupling agent and requires fewer shocks compared to petroleum jelly and other agents | In vitro study | - | Moderate | (13) | |
| Stone targeting | No difference in stone-free rate is seen in patients targeted with ultrasound versus fluoroscopy | Randomised controlled trial | 1b | High | (14) |
| Careful imaging control of stone localisation may contribute to quality of SWL outcome | Outcomes research | 2c | Moderate | (15) | |
| Timing | No trials investigating optimal timing of SWL sessions | – | – | – | – |
| Patient analgesia | Adequate patient analgesia is important to reduce excessive respiratory and pain-related movements. Higher SFR is seen in SWL performed under general anaesthetic vs. sedation | Cohort study | 2b | Moderate | (16,17) |
| Opioids and NSAIDs provide safe and effective analgesia for SWL | Meta-analysis | 1a | High | (18) |
GRADE, Grading of Recommendations, Assessment, Development and Evaluations; SWL, shock wave lithotripsy; PDI, percussion, diuresis and inversion; SPM, shocks per minute; SFR, stone-free rate; NSAIDs, non-steroidal anti-inflammatory drugs.