[Pain and extracorporeal lithotripsy for calculi of the upper urinary tract]

This study evaluates, 1) the pain induced by extracorporeal shock wave lithotripsy for renal stones using a piezo-electric shock wave lithotriptor (EDAP LT 01) and 2) the predictive factors for severe pain leading to an indication for analgesia. The relationship between extracorporeal shock wave lithotripsy intensity and pain intensity is evaluated by a numerical scale at the beginning of the session (T0), after 15 min (T15) and after 30 min (T30). At the end of the session, patients are categorized by one of us using a three-point scale which integrates the pain and the maximum tolerable intensity. These two types of evaluation are well correlated. Successive levels of stimulation are well discriminated by patients. Habituation is observed during the session for patients with low-level pain. In 28% of the patients, the intensity of pain required analgesia. Pain cannot be predicted by age, anxiety state, side of the stones and size, diameter of the contact between patient and convergence dome. In contrast, three parameters are correlated with the pain level: The L1 distance of renal parenchyma and the L2 distance skin-stone crossed by the piezoelectric waves, the size of the stone. The superior caliceal, middle caliceal and pelvic stones are significantly the most painful. These predictive variables can be easily measured before extracorporeal shock wave lithotripsy.