Q. A 57-year-old woman comes to her gynecologist for a 2-month history of urinary incontinence. She has been leaking small amounts of urine whenever her bladder is full and also she has a continuous feeling of incomplete urination. Her past medical history is significant for cervical cancer treated with surgery and radiation last year. She is otherwise healthy and not on any medication. Her temperature is 98.6°F (37°C), pulse is 90/min, blood pressure is 128/80 mmHg, and respirations are 14/min. Physical examination is unremarkable. Urinalysis is negative for RBCs, WBCs, and bacteria. Post-void residual urine is 250 mL. What is the most likely cause of her symptoms?