Repeated ESWLS...lithotrypsies

[Julie-West]

  I have a history of kidney stones.  I had my first ESWL about 18 mo. ago for two stones, 6 & 8MM.  It was not completely successful so had a second done 6 wks later.  I have several small "leftover" pieces which are now causing some chronic bleeding.  My urologist is recommending a third ESWL.  My question is, have there been any longitudinal studies regarding the safey, potential side effects or problems of repeated ESWL treatment?  I do have a history of mild hypertension which, incidentally, may be coincidental to the development of these large stones.  Additionally my physician has recommended I take higher (2000 mg/day) of Vitamin C to acidify my urine.  I understand that in itself may be problematic.  Thank you.    

[hfhs M.D.-AK]

Dear Julie,

Background:
-ESWL is a treatment procedure in which kidney or ureteral stones are pulverized noninvasively by shock waves into small fragments, which can be passed spontaneously.
-introduced in 1980 and now used in 80% 0f all patients with calculous disease.
-high intensity shockwaves are generated extracorporeally(outside the body),coupled into a patients body, and focussed on the stone..
-Goal is to use high intensity shock waves to comminute(break) renal and ureteral calculi without damaging the surrounding tissue.
-stone fragmentation is accomplished  on the basis that the accoustic impedance(density) of renal calculi is significantly different from its surrounding tissue.
Basic Principles:
Acoustic impedance- the definition of acoustic impedance is defined by the product of the density and the wave speed of a material, is an intrinsic property of the material.  When a shock wave propagates through different materials, the acoustic impedance determines the amount of energy that can be transmitted.  If the impedance is similar than the majority of the energy is transmitted.  However if the tissues impedance are dissimilar than energy is reflected and transmission will our at this boundary. In the cases of renal or ureteral calculi, the reflected and transmitted energy as this impedance boundary is sufficient to overcome the intrinsic strength of the stone leading to fragmentation.
There are also three different types of lithotriptors, Electromagnetic, Electrohydraulic, and Piezoelectric.  Each type of lithtriptor has its positive and negative points ,however the electrohydrolic lithotriptors tend to have a lower retreatment rate.
Also there are multiple types of stones.  Some stones, such as cysteine stones, are more difficult to break with lithotripsy.  
In terms of safety, the potential side effects are minimal.  One of the complications is hypertension and this may be a reason to limit the number of ESWL’s however this has never been shown to be a long-term problem.  This is termed a relative contraindication to the surgery.
The only other comment I have about your therapy is the addition of Vit C.  Your doctor needs to be sure you have infectious(struvite) stones or acidification of the urine will not help, only potentially hurt.  Vit C is broken down in the body to Oxalate, a compound that is a contributor to the most common type of stones, Calcium Oxalate.
Recommendations:
I think repeated ESWL is a safe operation however due to the size of the stone I think they should have been dissolved on passed attempts.  A good stone work-up, particularly if you are a young woman, might identify what type of stone you have.  If ESWL fails again, I would recommend direct visualization of the stone and possible direct removal.  This may be accomplished by Ureteroscopy.
This information is provided for general medical educational purposes only.  Please consult your physician for diagnostic and treatment options pertaining to your specific medical condition.  More individualized care is available at the Henry Ford Hospital and its satellites (1 800 653-6568).
Sincerely,
HFHS M.D.-AK
*keyword:ESWL