Extra-corporeal shochwave lithotripsy

EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY
Extracorporeal shock wave lithotripsy has revolutionized the treatment of urinary stones. The concept of using shock waves to fragment stones was noted in the 1950s in Russia. The first of these was made in Germany by the Dornier Company
The first clinical application with successful fragmentation of renal calculi was in 1980. The HM–1 (Human Model–1) lithotripter underwent modifications in 1982 leading to the HM–2 and, finally, to the widespread application of the HM–3 in 1983). Since then, thousands of lithotripters have been put into use around the world, with millions of patients successfully treated.
All require an energy source to create the shock wave, a coupling mechanism to transfer the energy from outside to inside the body, and either fluoroscopic or ultrasonic modes, or both, to identify and position the calculi at a focus of converging shock waves.
They differ in generated pain and anesthetic or anesthesiologist requirements, consumable components, size, mobility, cost, and durability.

Shock wave physics
In contrast to the familiar ultrasonic wave with sinusoidal characteristics and longitudinal mechanical properties, acoustic shock waves are unharmonic and have nonlinear pressure characteristics. There is a steep rise in pressure amplitude that results in compressive forces. There are 2 basic types of shock wave sources: supersonic and finite amplitude emitters.

Preoperative evaluation
Physical examination should be as thorough as in preparation for any other surgical procedure. Vital signs including blood pressure should be noted. Body habitus including any gross skeletal abnormalities, contractures, or excessive weight (>300 lb) may severely limit or preclude ESWL. Borderline individuals require simulation before treatment.

Intraoperative considerations
a. Stone localization—Proper patient positioning is a prerequisite for successful lithotripsy. Palpating the patient’s ribs and pelvic bony girdle can approximate appropriate positioning. Anterior located kidneys, medial oriented portions of a horseshoe kidney, or transplant kidneys are best treated in the prone position. Understanding positioning options with the various lithotriptors available today is required to optimize therapy.
Small or poorly calcified calculi can be difficult to image with fluoroscopy, irrespective of their location. Placing a ureteral catheter identifies known anatomy and supplies an injection port for radiocontrast agents. A poorly calcified caliceal calculus can be identified by injecting dilute contrast agents into the collecting system and then focusing on the appropriate calyx or filling defect.
Intravenous contrast agents may be also used.


b. Fluoroscopic imaging
Dimmed room lighting, and adequate bowel preparation to decrease bothersome bowel gas and thus decrease radiation exposure and improve the quality of the fluoroscopic image.
Intermittent fluoroscopy reveals movement of calculi with respiration and is helpful in locating and focusing on offending calculi.
c. Ultrasonic imaging
Ultrasound localization has the advantage of eliminating radiation exposure to the patient or the lithotripsy team. Ultrasound images may be confusing when multiple stones or stone fragments are present.

d. Coupling—Successful fragmentation requires effective coupling. Coupling devices should have properties similar to those of human skin. Optimal systems should prevent pain, ecchymoses, hematomas, or skin breakdown.

E. Shock wave triggering
Triggering shock waves with the electrocardiogram was originally performed to decrease cardiac dysrhythmias. The lithotriptor would sense the large swing of the QRS complex and initiate the shock wave 20 ms later; this would decrease shock waves during the repolarization phase of the cardiac cycle (myocardium is most sensitive during this time). If cardiac dysrhythmias occur, interruption of the procedure frequently stops them. However, if they continue, standard medical therapy is effective.

f. Fragmentation
Safe shock wave dosage is unknown. Shock waves induce trauma, including intrarenal and perirenal hemorrhage and edema, and thus the minimal shocks needed to achieve fragmentation should be given.

Postoperative care
Patients should be encouraged to maintain an active ambulatory status to facilitate stone passage. Gross hematuria should resolve during the first postoperative week. Fluid intake should be encouraged. Follow-up in approximately 2 weeks for discussion and evaluation of a KUB and renal ultrasonography will help assess success of fragmentation and passage of gravel.








• The most important factor in determining treatment of stone with ESWL
1. Stones factors
Stone size, Stone location, stone composition and stone number
2. Patient-related factors
Such as age, weight, shape, comorbidity, kidney position (normal versus pelvic), and whether the stone is in a solitary kidney. Of course, patient choice is also a factor.

Stone-free rates for solitary stones within the kidney following ESWL according to stone diameter are:
1. <1 cm 80%
2. 1-2 cm 60%
3. >2 cm 50%.
Stones within lower pole calyces are less likely to fragment and clear than those in middle and upper pole calyces
• Indications
1. Stone 1.0-2.5 cm
2. Recurrent stones
3. Recurrent UTI
4. Renal colic /chronic pain
5. Obstruction
6. Decreasing renal function


• Contra-indications of ESWL
Absolute
1. Pregnant women.
2. Patients with large abdominal aortic aneurysms.
3. Uncorrectable bleeding disorders.
4. Individuals with cardiac pacemakers should be thoroughly evaluated by a cardiologist. If ESWL is contemplated, a cardiologist with thorough knowledge and with the ability to override the pacemaker should be present in the lithotripsy suite.
5. Combined pathology; renal stone with renal cancer, hydatid cyst.
Relative
6. Abnormal kidney shape, position, horse-shoe kidney, variant vessel….etc.
7. Sever UTI
8. Stone ? 2.5 cm
9. Correctable bleeding disorder
10. Patient on cytotoxic drug, immune-suppressive treatment.
11. Patient with chronic disease like H.T., D.M. , renal failure
12. Over-obesity / musculoskeletal deformities.




Complications of ESWL
1. Pain; renal, ureteric or abdominal.
2. Frank hematuria
3. Renal /peri-renal hematoma ? CT scan
4. H.T. (still not certified)
5. Stone obstruct the ureter ; H.U.N., / bladder stone
6. UTI /septicemia
7. Chronic pyelonephritis
8. Failure of ESWL