The symptoms you are describing are often caused by benign prostatic hypertrophy but can also be secondary to prostatitis. Therefore, a prostate exam is warranted. Patients who experience decreased urine flow with a physical exam suggestive of an enlarged prostate are often put on a trial of flomax (tamsulosin). A painful prostate suggests prostatitis and these patients are often put on antibiotics and anti-inflammatories.
Other causes of decreased urine flow and decreased flow of semen include urethral strictures, urinary tract infections, drugs (nasal decongestants, antidepressants, allergy medications), or neurologic disorders.
