UPSTREAM is a randomised controlled trial in men who have bothersome difficulty passing urine and who are considering having surgery for the symptoms. The group studied will be men who continue to be bothered by difficulty passing urine, despite initial treatment such as drugs, where symptoms are thought to be due to bladder outlet obstruction. The men will be assigned at random to either invasive urodynamic tests as well as the standard tests ("Invasive urodynamics") or to the routine standard tests ("Usual care" control arm) alone. Routine standard tests include asking men to complete a questionnaire (the International Prostate Symptom Score (IPSS)) and a bladder diary, carrying out flow rate testing, and checking the urine for infection. Some surgeons also use "discretionary tests" such as the PSA cancer-screening blood test.