Cystometry

Cystometry is the key test of the urodynamic assessment. It consists of measuring the pressures inside the bladder while it is gradually filled with saline solution, and then during the emptying phase. This test provides essential information on the behaviour of the detrusor muscle. During the filling phase, cystometry assesses bladder sensation (first desire, normal desire, urgent desire to void), bladder compliance (the ability of the bladder to distend without an excessive rise in pressure) and detrusor stability (the absence or presence of involuntary contractions). During the emptying phase, the test measures the detrusor contraction pressure and assesses the coordination between bladder contraction and relaxation of the urethral sphincter. These data are essential for distinguishing bladder outlet obstruction from detrusor underactivity. Cystometry is indispensable in the diagnosis of unstable bladders, poorly compliant bladders and detrusor-sphincter dyssynergia, and in the pre-operative evaluation of many urological conditions.