The post void residual urine (that is left in the bladder after urinating) is essentially stagnant urine, which like stagnant water, is prone to infection. This is why some men who previously never had a urinary tract infection (UTI) can start to get them after developing BPH.
The initial treatment of BPH is generally with a medication called an alpha blocker (e.g., Flomax, alfuzosin, Rapaflo). These medications help to relax smooth muscles in the prostate to take some of the pressure off the urethra. Unfortunately, these medications often have side effects including dizziness, decreased energy, and/or retrograde ejaculation.
Another class of medications is 5α-reductase inhibitor (e.g., finasteride or dutasteride). Unfortunately, these medications have a high rate of causing decreased erectile function, decreased energy, and decreased libido.
When a patient cannot or chooses not to tolerate the side effects of BPH medications, or if they are not effective, the next step is to look into a BPH treatment procedure.