Urinary retention describes the inability to fully empty the bladder during urination. In males the most common cause is a benign enlargement of the prostate gland, although it can also be caused by issues with nerves, constipation, infection and some medications. In most cases, it manifests as delayed or intermittent urination. In rare cases, the flow of urine stops completely and the bladder continues to enlarge. The latter is a medical emergency. If the bladder is not emptied in this situation, urine can back up in the ureters and affect the kidneys, resulting in kidney failure and sepsis.