New Method for Calculation of Bladder Wall’s Distensibility Using Evaluation Software

Sándor LOVÁSZ1, Péter TENKE1, László LOVÁSZ2

1Urological Department, Jahn Ferenc Teaching Hospital, Budapest, Hungary
2Department of Computer Science of the Eötvös Loránd University, Budapest, Hungary

Aim: Precise measurement of volume-pressure dependence of the
bladder in a wider range of pressure indicates a nonlinear relation,
proving that conventional compliance calculation is inexact thus
inappropriate to define elastic properties of the bladder wall.

Methods: We measured intravesical pressure during continuous filling
in the wide range of 0–80 cmH2O pressure as a part of hydraulic
distension of the bladder in interstitial cystitis patients. In order to
rule out high pressure induced iatrogeny caused by vesico-renal reflux
and inexactness caused by leakage, we were filling a special balloon
catheter inside the bladder. Intravesical pressure was measured inside
this balloon indirectly, through balloon’s wall. Perivesical (intraabdominal)
pressure was observed as pressure of reference.

Results: Pressure-volume correlation can be best described by a
composition of two parabolic curves. This had been proven by
using our newly developed evaluation software. Based on this
finding an other software automatically evaluates measured data
and calculates best fitting parabolic curves. Volume at the breaking-
point of the two curves defines basic capacity of the bladder.
Distensibility can be defined as the coefficient of the second
parabolic curve divided by basic volume.

Conclusion: Basic volume and distensibility coefficient, the newly
defined quantitative parameter, objectively measure physical characteristics
of bladder wall, letting us improve diagnosis and follow
up of processes deteriorating bladder function.