Extracorporeal lithotripsy is a method of fragmenting a kidney stone by shock waves (that is, a particular form of energy) by avoiding traditional surgery. It’s proven effective and has been used around the world for around 20 years. In particular, urethral extracorporeal lithotripsy is the treatment by shock waves of a kidney stone located in the ureter, that is, in the channel leading the urine from the kidney to the bladder.
The indication of extracorporeal therapy of a urethral stone is placed by the urologist when the stone size does not make it probable the spontaneous expulsion or when the presence of the stone, although spontaneously eliminated in theory, causes complications in the urinary tract (recurrent infections, urinary tract obstruction, etc.), which make it advisable to have a quick resolution. The bigger is the size of the stone (more than 4 mm) the less easy will be a spontaneous expulsion.
However, the indication of shock waves extracorporeal lithotripsy depends on several factors:
- Calculation size:
Excessive calculation dimensions make incomplete fragmentation unlikely, and too small dimensions do not allow it to be treated with shock waves;
- Location: extracorporeal lithotripsy has maximum efficacy in the first third (lumbar ureter) and in the last ureter (iuxtavescical ureter) tracts;
- Number of stones: the presence of numerous stones in the ureter can make more sense to adopt alternative methods;
- The type of calculation: some stones are particularly resistant to shock waves (e.g. cystine stones) or are radiolucent (uric acid stones). In these cases, missed radiographic visualization and difficult ultrasound location may require alternative treatment;
- The duration of the stay of a ureter stone is a factor limiting the effectiveness of extracorporeal lithotripsy. The stone can in fact stick tightly to the wall of the ureter and not be eliminated even if fragmented;
- Anatomical conditions: stenosis (narrowing) or anatomical anomalies that hinder urine transit are contraindications to extracorporeal lithotripsy. Because lithotripsy is effective and does not cause complications, the urine outflow and the elimination of the fragments must be guaranteed;
- Patient conditions: coagulation anomalies, obesity, pregnancy, severe bone deformity may hinder the use of extracorporeal lithotripsy.
The patient is placed on the lithotripsy tool bed in the supine position, keeping as still as possible, in order to allow the greatest number of “shots” to score. The intensity of the strokes is variable: it begins with low intensity strokes, raising them progressively. The patient feels the stroke in the “bombed” region that, with treatment, may become sore.
In some cases, in conjunction with extracorporeal treatment, ureteral catheterisation may be necessary both to make the calculation more visible and to push it to a point where it can be more easily affected by the shock waves (even up to the kidney).
Preparation for intervention:
Treatment does not require special preparation despite the need for certain examinations (ECG, chest RX, blood and urine tests) to allow patient sedation for endoscopic maneuvers or when the treatment is poorly tolerated, when necessary. Antibiotic prophylaxis can be performed to prevent infection. In particular cases, urine derivation may be indicated prior to treatment, via internal (double J) or external stent (percutaneous nephrostomy) to allow for the preservation of renal function in the event of ureteral obstruction by the stone.
The ureteral or nephrostomic tutor can be left for prolonged periods of time (even weeks). Good intestinal preparation is always advisable in order to properly view the stone to be treated.
Duration of intervention:
This is a relatively short procedure, which generally does not exceed 45 minutes, including the time needed for radiological and ultrasound tests. Longer duration may be necessary if the treatment requires complementary contextual endoscopic maneuvers.
Type and duration of hospitalization:
Treatment can be performed in Day Hospital in more than 90% of cases. It may rarely require a longer stay.
For the proximal ureter the average success rate reported in the literature is 81%. For the middle ureter is 79%. For distal ureter is 85%.
The advantage of the method is to allow complete resolution of ureteral stone in about 80-90% of cases avoiding any endoscopic or surgical intervention. In addition, with the equipment currently in use, it is a well-tolerated treatment that generally does not require anesthesia.
Although in 70-80% of cases only one treatment is needed, sometimes this has to be repeated (larger size stones can take 2 or more treatments).
In 10 to 15% of cases, endoscopic or, rarely, surgical maneuvers are required to resolve the stone. Expulsion of fragments can take prolonged periods, even months, in relation to the location and the size of the stone.
It may be necessary to expose to radiations for a relatively long period of time to display the stone and to monitor the correct pointing during lithotripsy. Radiation exposure is more relevant if the stone is not visible to ultrasound.
The expulsion of the fragments may result in painful reno-ureter colic. Hemorrhage is a very common occurrence.
Failure to eliminate fragments and their stacking in the ureter risk the dilation of the kidney and ureter and, above all, the superimposed infection. In addition to the antibiotic therapy of the infection, the obstruction must be resolved: this can be achieved by ureteral catheterisation or percutaneous nephrostomy. In some cases, extraction of the fragments may require ureteroscopy and, in rare cases, surgery.
The most serious risk is urinary sepsis that may require nephrectomy. The risk of retroperitoneal bleeding in ureteral lithotripsy is extremely low.
Warning at discharge:
Hyperhydration is recommended in order to eliminate fragments more quickly. A short period of antibiotic prophylaxis is always useful.
How to behave in case of complications arising after discharge:
If a simple kidney colic occurs, this can be treated by the a trusted physician. If colic is added to a high and persistent fever, it is necessary to perform an ultrasound and refer to the urological center.
The solution to the problem must be documented with direct abdominal Rx and ultrasound (especially in radiotransparent calculations). These exams must be practiced within 1-2 months of treatment. Urography can be practiced at 6 months.