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EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY (ESWL) Removal of Stones without Surgery

U G Oza*, Hema K**
*Consultant Urologist, Bombay Hospital Institute of Medical Sciences, Mumbai 20. **Consultant Urologist, Colony Nursing Home, Mumbai 400 019.

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Throughout history of medicine, perhaps no technological advance has produced a more revolutionary effect than extracorporeal shock wave lithotripsy (ESWL). This is a technique by which stone can be broken by shockwaves generated outside body and focussed on the stone. Two decades ago talking about treatment of stone without surgery would have been considered as a fairy tale. But today it’s a reality.

Lithotripsy is the brainchild of engineers of Dornier Laboratories in Germany. They observed that during high speed flight, shock waves generated by collision with raindrops caused pitting on the metal surfaces of supersonic aircraft. Dr. Christian Chaussey and his colleagues at Munich with techologists of Dornier laboratories succeded in using this principle to treat kidney stones by developing lithotripsy machine. Dr. Chaussey successfully treated first patient of kidney stone by this machine on 7th February, 1980. Today, there are many more machines available, which are compact, relatively cheaper and easy to handle. This has helped many centres to offer this treatment at a reasonable rate to the patients (Fig. 1).

Mechanics

Shock waves are generated by different types of generators. Commercially available lithotriptors use electrohydraulic, electromagnetic or piezoelectric generators. These shock waves are focussed by acoustic mirrors and then shock wave coupling allows these waves to be propagated through water medium in the body. Stone localisation by X-ray (C-arm) or ultrasound allows for precise placement of stone in focal area of a shockwave generator. Once focussed, these waves break the stone.

Shock waves give rise to mechanical stresses in brittle material such as kidney stones. Repeated shock waves impact eventually will exceed the comprehensive strength of the stone and bring about its disintegration. Fragments are subsequently passed in the urine.

Advantages

Fig. 1: ESWL machine

This technique has become most popular and treatment of choice for stone disease. It has definitive advantages.

1. No incision or cut required.
2. No hospitalisation, as it is an OPD procedure.
3. No anaesthesia required, hence even medically high risk patients can be offered this option.
4. No pain or minimal pain,
5. All age group patients can be treated.

Contraindications

1. Pregnancy
2. Uncontrolled coagulopathy
3. Uncontrolled hypertension
4. Distal obstruction in urinary tract
5. Non functioning kidney
6. Presence of active infection

Clinical Applications

Success of ESWL treatment depends on many factors. Every stone in urinary tract may not be suitable for treatment by this technique. Various factors are to be considered before deciding the treatment. Patients have to be explained about its limitations and failure. Some stones will require multiple sittings (Fig. 2).

a) Stone Composition : Calcium oxalate dihydrate stones are more fragile and break easily whereas cystine and calcium oxalate monohydrate stones fragment poorly.

b) Size of the Stone : Stone free rates after ESWL decrease as stone size increases. At present most machines break stones upto 2 to 2.5 cm effectively. Bigger stones may require combined therapy with PCNL or even open surgery (Fig. 3).

c) Position of the stone : The best stones to break are stones in renal pelvis. Stones in calyces can also be broken but success rate varies. Upper ureteric stones can be broken with ESWL, but middle ureteric stones are difficult. Lower ureteric stones are best treated with ureteroscopy when indicated.

Fig. 2 : Plain X-ray KUB and IVP . Ideal stone for ESWL.

 

Complications

1. Steinstrasse - this means street of stones. Fragments of stones can block the ureter and obstruct the kidney. This may clear by itself or sometime require help of percutaneous nephrostomy or ureteroscopy to retrieve the fragments. This may be prevented by inserting DJ stent when stone is bigger or in solitary kidney (Fig. 4).
2. Mild peri renal haematoma may be seen.
3. Urosepsis can sometimes be life threatening.

Fig. 3 : Large multiple stones - not good for ESWL operation - treatment of choige plain X-ray, IVU film and clearance after surgery	Fig. 4 : "Stainstrasse" - Broken fragments, which were cleared.

Preparation for ESWLThough the procedure sounds simple, it has its own problems. Every patient has to be investigated as in any surgical procedure including proper history taking, physical examination, urine culture, haematocrit, renal biochemistry, plain X-ray of kidney, ureter and bladder with ultrasound of urinary tract.

But we believe IVP (Intra venous pyelography) must be done in every patient, unless specifically contraindicated. It gives a fair idea about function of the kidneys, helps in proper localisation of stone and in detecting obstruction in urinary tract. It is a road map for urologist as patient may require ancilliary procedures like DJ stenting, ureteroscopy or PCNL sometimes to make patients stone free or in tackling fragments of broken stone. For a large stone or in a solitary functioning kidney it is advisable to place DJ stent before starting lithotripsy to prevent steinstrasse (Fig. 5).

Infection has to be well controlled with preprocedural antibiotics and has to be continued even after the procedure. Some patients require sedation during the procedure.

Adequate hydration during the procedure and after the procedure is key to success. Surprisingly in most stone formers water consumption is low and their urine output is also inadequate.

After the treatment follow up is necessary till patient is stone free. Periodical checkup is required to check about recurrence of stone disease as it is a dictum - "Once a stone former can always be a stone former".

Fig. 5 : DJ Stent

CONCLUSION

ESWL has revolutionised the management of stone disease. Truly it is one of the wonders of this century. But it is not as simple as it sounds. It has its own limitations. Selection of patients, selection of stone and when performed by an expert gives the best results. It is not the machine, but the man behind machine that is important. He has to be knowledgeable about various procedures like DJ stenting, ureteroscopy, PCNL etc. to give best results to the patients, without morbidity. When this treatment is done by untrained personnel it increases the morbidity and can give bad name to the procedure.

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