Extracorporeal shockwave lithotripsy (ESWL)
Since its introduction in the early 1980’s, ESWL has become the main therapeutic option for the majority of renal and ureteric stones. It has also been used for the treatment of bladder calculi. Since its inception, shock wave technology has undergone a number of alterations, although the basic concepts remain the same. The shock waves are high-energy amplitudes of pressure generated in air or water by an abrupt release of energy in a small space. They are propagated through water and soft tissues with little impact but exert enormous energy when they encounter a boundary between substances of differing acoustic impedance (such as a stone). Repeated shock waves fragment the stone into small pieces - ideally ‹2mm - which are then passed spontaneously. The treatment is usually performed with simple analgesia only and in an outpatient setting. All lithotripters are made up of four basic components: an energy source, a focussing device, a coupling medium and a stone localisation system.
Success rates of up to 90% have been reported in the treatment of renal calculi ‹2cm in diameter. However, larger calculi and those located in the lower pole of the kidney fare worse and should be considered for a surgical alternative. The management of ureteric calculi has changed greatly with the developments in ESWL technology and all upper ureteric, most middle and some lower ureteric calculi are now amenable to ESWL. Much of the success of ESWL for ureteric calculi is dependent upon immediate access to the service and in this situation ureteric stents can be avoided and two treatments can be performed within a week with success rates similar to ureteroscopy with a lower morbidity. However, in the UK this level of service is only available in a few areas and often patient will undergo ureteroscopy with or without a stent in order to treat an urgent clinical problem.
There are a number of well-recognised complications associated with ESWL; these include ureteric colic, steinstrasse (impacted fragments in the ureter) infection and perinephric haematoma. The question of whether ESWL leads to significant renal damage and hypertension remains unanswered. There are a few contra-indications to ESWL and these include anticoagulation, pregnancy and an abdominal aortic aneurysm.