BPH is a common condition that affects pretty much all men above a certain age. The FAA has a list of approved drugs for treatment (
http://www.leftseat.com/medcat1.htm). Regarding surgery, I would think that this shouldn't be a problem for your medical if you can prove good recovery after surgery and don't have to take any drugs not approved by the FAA. As always, it pays to discuss this with your AME.
Greetings, -- Chris.
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Read about my trip across the USA in an MT03 gyro
here.