A 58-Year-Old Woman Comes to the Office Due to Leakage

A 58-year-old woman comes to the office due to leakage of urine.  The patient has had increased urinary frequency over the last 3 months, often voiding 1 or 2 times every hour and multiple times each night.  She has difficulty initiating urination and voids a small volume of urine.  The patient now has continued leakage of urine, requiring her to wear an incontinence pad.  She has no dysuria or hematuria.
The patient has a history of depression and switched from sertraline to amitriptyline 4 months ago.  She underwent a total abdominal hysterectomy 2 years ago for endometrial hyperplasia.  She does not use tobacco, alcohol, or illicit drugs.
BMI is 30 kg/m².  Vital signs are normal.  Abdominal examination reveals a lower abdominal mass.  Pelvic examination reveals continuous leakage of urine from the urethra; no pooling is seen in the vaginal vault.  A small amount of urine is leaked with cough-stress test; postvoid residual volume is 500 mL.
Which of the following is the most likely diagnosis in this patient?

A) Interstitial cystitis
B) Overflow incontinence
C) Urethral diverticulum
D) Urgency incontinence
E) Vesicovaginal fistula