Review Question - QID 211096

A 35-year-old woman arrives to the clinic complaining of progressive urinary leakage that has occurred for the past 1 year. At first, she would notice leakage only during athletic exercise, but now the incontinence occurs even when she laughs or coughs. The patient states that she goes to the bathroom more frequently to try to prevent “wetting myself.” She wakes up once a night to urinate. She denies dysuria, hematuria, abdominal pain, and abnormal vaginal discharge. The patient has bipolar syndrome and takes lithium. She had an uncomplicated vaginal delivery 10 years ago and a cesarean section 4 years ago. She has had no other surgeries. She drinks at least 6 glasses of water a day but may drink more on days she goes for a long run. She also has a large coffee in the morning and another coffee mid-day if she “needs to focus.” The patient denies tobacco, alcohol, and other recreational drug use. Her temperature is 98.7°F (37°C), blood pressure is 112/71 mmHg, pulse is 81/min, respirations are 12/min, and oxygen saturation is 98% on room air. Pelvic examination and speculum examination are unremarkable. When that patient is asked to Valsalva, leakage of urine is observed. A urinalysis, including specific gravity, is within normal limits. A beta-human chorionic gonadotropin is negative. Which of the following is the most likely cause of the patient’s symptoms?