In patients suffering from colics due to calculosis of one upper urinary tract the evolution in time of referred parietal hyperalgesia after stone fragment elimination promoted by extraeorporeal shock wave lithotripsy (ESWL) was studied.
Before ESWL, all patients presented clinical evidence (positivity to dermographism and Head's procedure, pinch palpation, digital pressure and Giordano's manoueuver) and instrumental signs (significant lowering of pain threshold to electrical tissue stimulation) of cutaneous, subcutaneous and muscular tissue hyperalgesia in the lumbar region of the affected side.
After ESWL, hyperalgesia decreased in the three tissues, as shown by progressive change in the clinical tests and an increase in pain threshold to electrical stimulation in relation to the extent of stone fragment expulsion. In the stone-free condition, hyperalgesia had disappeared in the skin but remained to a mild and moderate extent in the subcutaneous tissue and muscle respectively.
It is concluded that the persistence in time of referred hyperalgesia is only in part linked to the continuing presence and activity of the stone in the urinary tract. To a certain extent, the phenomenon seems to become independent of the primary focus, possibly as a result of plastic neuronal changes in the central nervous system which, triggered by afferent visceral inputs, are maintained even after their removal.