The purpose of the lower urinary tract is to allow for low-pressure bladder filling and storage of urine without incontinence and voluntary complete expulsion of urine. This is made possible by an intricate balance of neural control, numerous neurotransmitters, subtle anatomic relations, and a variety of pharmacological and mechanical properties. This complex system can be simplified into the two phases of the micturition cycle: bladder filling with urine storage and bladder emptying or voiding.1 The focus of this chapter will be on problems that women face in regard to their ability to successfully empty their bladder, termed voiding phase dysfunction.
In the simplest terms, the micturition/voiding phase requires a detrusor contraction that is of sufficient strength and of sufficient duration to overcome the resistance of the bladder outlet. Any alterations, or combinations of alterations, that affect the strength/duration of the detrusor contraction, that increase the resistance of the outlet, or that affect the coordination of these actions, are potential causes of impaired emptying. Ineffective or incomplete emptying can be caused by a problem with the bladder (impaired or absent contractility) or a problem with the outlet (obstruction—anatomic or functional). Table 8-1 shows a list of possible physiological causes of impaired emptying based on this functional classification. One must be careful in making a clinical diagnosis of “acontractile” or “hypocontractile” bladder, as behavior during urodynamics may not mimic that of daily living. For example, if a patient normally voids yet cannot do so during a urodynamics study, she may not truly have an acontractile bladder.
Etiology of Voiding Phase Dysfunction
The micturition/voiding phase requires a detrusor contraction that is of sufficient strength and duration to overcome the resistance of the bladder outlet.
Ineffective or incomplete emptying can be caused by a problem with the bladder (impaired contractility) or a problem with the outlet (obstruction).
This chapter will review the pathophysiology underlying the different etiologies for common conditions causing ineffective emptying, general evaluation of voiding dysfunction, followed by treatment options for each condition.
Detrusor underactivity is defined by the International Continence Society (ICS) as a contraction of ...