Shock Wave Lithotripsy (SWL)
During this procedure, sound wave energy is used to break stones within the kidney or ureter into small fragments that gradually leave the urinary tract. Because the sound waves are delivered through a treatment probe positioned against the skin of the back, most patients can be treated without inserting any instruments into the urinary tract. When larger stones are treated, however, your surgeon may choose to place a temporary stent prior to the SWL procedure to ensure that the ureter does not become blocked by multiple fragments.
Before the procedure:
You will undergo an office interview with physical examination. Any needed blood tests will be scheduled prior to your surgery. X-rays will be obtained to localize the stone, measure its size, and confirm that it is easily visible, as x-ray targeting is used to locate the stone during treatment.
Risks of the procedure:
Some stones can be very hard and dense and may resist fragmentation. As a result, the stone may not break up well enough to allow the pieces to pass from the urinary tract. When this happens, other surgical procedures may need to be used to completely clear the remaining stone fragments. The stone's location can also affect the success of SWL. For example, stones within the lower (most dependent) portion of the kidney may fragment well but then not pass from the urinary tract, as gravity prevents them from leaving the kidney. Stones that are impacted, or wedged, within the ureter may also be more difficult to break apart. When treating a larger stone, fragments can sometimes become lodged within the ureter if a larger number are attempting to pass at the same time; this may require an additional procedure to relieve the blockage and also to remove any trapped stone fragments.
Contraindications to the procedure:
Patients with known stone compositions that are resistant to SWL (such as cystine) should not be treated with this procedure. Any active urinary tract infection must be treated prior to SWL. Also, patients with a known history of bleeding issues or who are on blood thinners should not undergo SWL because of the risk of significant bleeding within the kidney. SWL cannot be done in pregnant women. Finally, any patient with known anatomic factors that prevent adequate drainage from the kidney should not undergo SWL, as stone fragments will have a difficult time leaving the urinary tract.
After the procedure:
Patients typically go home the day of surgery. Some blood in the urine (hematuria) may be seen. In addition, you may have some pain during the passage of stone fragments. Your surgeon will see you within a couple of weeks after the procedure to obtain an initial post-operative x-ray to document that stone fragments are passing from the urinary tract. The process of fragment passage can take place over a number of weeks, and your surgeon will arrange for further follow-up visits as needed to check upon your progress.