The effect of prostatectomy

3 pressure flow loops were performed both before and after transurethral prosatectomy The loops have gone from higher pressure to lower pressure. The shape has also changed from high to low gradient.

NB Despite the pressure changes the maximum flow rate has not changed much. This is because of the shape of the BOR. Decreasing urethral resistance starts to move the voiding point down the BOR as in the diagram below
But if it starts quite far up then there will be large pressure decrease before significant flow increase. Clinically it is the pressure that matters more so flow rate alone is not necessarily a good indicator of clinical improvement

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