Chapter 61 Urinary Incontinence: Bypass, Overflow
INTRODUCTION
Description: Urinary incontinence is a sign, a symptom, and a disease all at the same time. Bypass incontinence is continuous incontinence occurring when the normal continence mechanism is bypassed, as with fistulae. Symptoms may be intermittent or continuous, making the establishment of a diagnosis difficult in some patients. Overflow incontinence is continuous or intermittent insensible loss of small volumes of urine resulting from an overfilled or atonic bladder.
Prevalence: Of all women who have hysterectomies, 0.05% develop a fistula and subsequent bypass incontinence. Overflow incontinence is uncommon and generally follows trauma, instrumentation, surgery, or anesthesia.
Predominant Age: Mid-reproductive age and onward. Overflow incontinence is more common in later years.
ETIOLOGY AND PATHOGENESIS
Causes: Bypass incontinence—fistulae may result from surgical or obstetric trauma, irradiation, or malignancy, although the most common cause by far (in developed countries) is unrecognized surgical trauma (obstructed labor in other parts of the world). Roughly 75% of fistulae occur after abdominal hysterectomy. Signs of a urinary fistula (watery discharge) usually occur from 5 to 30 days after surgery, although they may be present in the immediate postoperative period.
Overflow incontinence—trauma (vulvar, perineal, radical pelvic surgery), irritation/infection (chronic cystitis, herpetic vulvitis, herpes zoster), anesthesia (spinal, epidural, caudal), pressure (uterine leiomyomata, pregnancy), anatomic defect (cystocele, retroversion, or prolapse of the uterus), neurologic disorder (multiple sclerosis, diabetes, spinal cord tumors, herniated disc, stroke, amyloid disease, pernicious anemia, Guillain-Barré syndrome, neurosyphilis), systemic disease (hypothyroidism, uremia), medications (antihistamines, appetite suppressants, β-adrenergic agents, parasympathetic blockers, vincristine, carbamazepine), radiation therapy, behavioral problems (psychogenic, infrequent voiding).
