Dynamic clearance: mathematical assessment of flow mechanics in prostatic resection

The understanding of flow mechanics in endoscopy is poor. In prostatic surgery, emphasis has been placed on limiting the rise of intravesical pressure with little regard to the effect on flow mechanics and visibility. A model has been developed using dynamic clearance to compare different methods of prostatic resection. The results show that in a 0.95-cm glass urethra, continuous flow irrigation has slower clearance at all flow rates when compared with intermittent irrigation and suprapubic suction. Although intravesical pressure is important, attention should also be paid to flow dynamics and more emphasis should be placed on this when new instruments and fluid delivery systems are developed.