Interview with Prof. Peter Rosier
Hypothesis / aims of study
Prostate enlargement may cause symptoms of lower urinary tract dysfunction in male patients. Intravesical protrusion of the prostate middle lobe (IPP) has been reported by various research groups as a specific type of prostate enlargement, relevant for management. Reports suggest that patients with IPP do respond to a lesser extent on alpha blocking therapy and recent single centre studies and expert opinions suggest that these patients could specifically benefit from surgery. The pathophysiology of the voiding dysfunction related to IPP is however poorly understood. A ‘ball valve’ obstruction type is suggested in some manuscripts, based on hypothesis or on cystoscopic appearance. IPP may be recognized on trans-rectal or trans-abdominal ultrasound, but the observation does not explain why IPP leads to failure of prostate (alpha-blocking) relaxing treatment.
Pressure flow analysis can be applied for the diagnosis and grading of bladder outlet obstruction and the detrusor pressure at maximum flow (PdetatQmax) has shown relevance in clinical practice. The ICS obstruction number (ICS-OBS) is based on PdetatQmax.
A pressure flow (P/Q) graph or – plot, showing the pressure and flow relation of the complete voiding however, provides additional information about the voiding process.
The ‘laws’ of distensible collapsible tube hydrodynamics are helpful in clinical interpretation of pressure and flow dynamics during voiding. Minimum pressure required to ensure flow is a measure of collapsibility and (Pdetat)Qmax is a measure of distensibility or ‘flow controlling zone’. Usually bladder outlet distension is maximal at the moment of Qmax. After Qmax the pressure and flow (and detrusor and outlet) are normally in balance and collapse of the bladder outlet is seen at the termination of flow.
Previous studies have shown that pressure and flow are however not perfectly balanced throughout the entire voiding in every patient. Some have demonstrated variety in slope and curvature, when compared to the ‘standard’ and ‘static’ passive urethral resistance relation.
We present P/Q – graph observations in patients with IPP as a step towards better understanding of voiding dynamics in these patients and have the aim to elucidate pathophysiology IPP dynamics and explain the relative resistance to pharmacotherapy of these patients.
Rosier P F W M, Department of Urology University Medical Centre Utrecht