Influence of density and viscosity of fluids on extracorporeal shock wave lithotripsy of gallstones in vitro.
BACKGROUND
It is hitherto still questionable which of the physical properties of the bile fluid influence the outcome of extracorporeal shock wave lithotripsy (ESWL).


METHODS
In this study the influence of the density and viscosity of bile simulating fluid on ESWL was tested in vitro by applying CsCl solutions of densities 1.0, 1.3, 1. 5, 1.7 and 1.9 g/ml. Five almost identical "sister" stones from one patient were fragmented in these five fluids. The number of shock waves required for adequate fragmentation (fragments < 4 mm) was measured for comparison. This was repeated on a further seven patients (five "sister" stones per patient). Subsequently, the influence of the viscosity of the fluid on ESWL was tested using polyethylene glycol (PEG) solutions of the viscosities 1, 5, 17, 30 and 59 mPa.s. Analogous to the first part of this investigation, 40 gallstones from an additional eight patients (again five almost identical sister stones) were fragmented, registering the number of shock waves required for adequate fragmentation.


CONCLUSIONS
The density of the fluid did not reveal any monotone correlation to the number of shock waves required. In contrast to the density of the fluid there was a distinct correlation (r subsets = 0.84; p < 0.001) between its viscosity and the number of shock waves required. On average, the number of shock waves required in a fluid with a viscosity of 59 mPa . s must be more than three times that required in water, which has a viscosity of 1 mPa.s.
Nitsche
R
R
1. Medizinische Universit-atsklinik, Schittenhelmstr. 12, Kiel D-24105, Germany.
Hinrichsen
H
H
Wilhelm
R
R
Fölsch
U R
UR
D002769:Cholelithiasis / Q000628:therapy*; D006801:Humans; D008096:Lithotripsy / Q000379:methods*