Relationship Between Patient Position and Pain Severity During Shock Wave Lithotripsy for Renal Stones With the MODULITH SLX-F2 Lithotripter: A Matched Case-Control Study

PURPOSE We evaluated the association between shock wave lithotripsy (SWL)-related pain and patient positioning during SWL. MATERIALS AND METHODS We retrospectively reviewed the medical records of 162 patients who underwent their first SWL session for single renal stones from May 2010 to August 2011. One hundred thirteen patients underwent SWL in the supine position and 49 did so in the lateral position. To evaluate an unbiased estimation of the positional effect on pain severity during SWL, both groups (supine vs. lateral) were matched according to sex, age, body mass index, stone location, and stone size. Thirty-four patients from each group were selected for analysis. Pain was evaluated with an average visual analogue scale (VAS-avg) and maximum visual analogue scale (VAS-max). Analgesic usage was also compared between the groups. RESULTS All patients (n=34) in the supine group had radio-opaque stones compared with only 47.1% of the patients in the lateral group (n=16). The VAS-avg and VAS-max of the lateral group were significantly lower than those of the supine group (1.2±1.0 and 3.1±1.7 for VAS-avg and 2.5±1.8 and 4.7±1.9 for VAS-max, respectively, p<0.05). However, analgesic usage between groups did not differ significantly (17.6% in the supine group vs. 5.9% in the lateral group, p=0.259). In a subgroup analysis confined to patients with radio-opaque stones, the supine group still suffered more pain. CONCLUSIONS Patients with renal stones suffered more SWL-related pain in the supine position than in the lateral position. During SWL, positioning of patients should be considered a predictive factor for SWL-related pain.