Predictive risk factors for pain during extracorporeal shockwave lithotripsy

Extracorporeal shockwave lithotripsy (SWL) is a noninvasive but painful procedure. The aim of this study was to identify predictive risk factors for pain during SWL.

Two hundred twenty-two SWL treatments with the Lithostar lithotripter (Siemens) were included in a monocentric study. Patient and stone characteristics were prospectively collected in a database, and a standardized pain control protocol was administered 1 hour before treatment: paracetamol, nefopam, ketoprofen, and alprazolam. Subjective pain level was assessed with visual analog scale (VAS, 0-10). If VAS was >or=3, tramadol was added. If VAS was still >or=3, shockwave intensity was decreased or treatment was interrupted. The efficacy on stone fragmentation was evaluated 1 month after treatment. The need for adjuvant analgesia was compared with patient and stone characteristics to find out predictive risk factors for pain.

The average subjective pain was 3.1. The need for supplementary analgesia was more frequent in women (p = 0.035), younger patients (p < 0.001), anxious and depressed patients (p = 0.018), in patients with previous SWL (p = 0.0185), in patients with a rib projected stone (p < 0.001), in patients with renal stones (p = 0.0535), and finally in patients with homogeneous stones (p = 0.02). Multivariate analysis revealed two independent risk factors for pain: young age (odds ratio = 5; p < 0.001) and rib projected stone (odds ratio = 5.23; p < 0.001). Stone fragmentation was worse in patients with an adjuvant analgesia requirement (p = 0.0311).

Predictive risk factors for pain during SWL treatments were found: young age, rib projected stones, anxious and depressed patients, previous SWL treatment, and homogeneous stones. A higher analgesic requirement is necessary for these preselected patients to perform SWL and optimize its efficacy.