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CHAPTER 26
of micturition and its relationship to the peripheral and central parts of the nervous
system in normal and pathological conditions. The history of this research over the last
60 years contains a considerable number of contributions which have been fundamental
in furthering the understanding of the innervation of the intricate process of storage
and emptying of the urinary bladder (Elliot, 1907; Barrington, 1914-41; Head & Rid-
doch, 1917; L.R.Miiller, 1918-31; Denning, 1924; Weston, 1920; McCrae, 1926;
Hovelacque, 1927; Stohr, 1928; Learmonth, 1931; Langworthy and his associates,
1933-40; Denny-Brown & Robertson, 1933; Evans, 1936; Munro, 1936-52; Talaat,
1937; McLellan, 1939; and others). The congregation of most patients with spinal cord
injuries in Spinal Units during the Second World War has been a new and acute incentive
to research on the pathophysiology of the human bladder and a vast literature on this
subject has accumulated. This has resulted in a greater awareness of the complexity of
the vesical dysfunction following complete and incomplete lesions of the spinal cord and
its effects on the function of the upper urinary tract as well as on the cardiovascular
system and other autonomic mechanisms. Yet, in spite of the advances made in the last
25 years in the development of sophisticated techniques of investigation of the urinary
tract, there still exist gaps in our knowledge. Controversial concepts have arisen regarding
both physiological aspects and the management of the abnormal vesical function.
The act of micturition
The act of micturition in physiological conditions with intact nervous control can be
defined as a co-ordinated powerful reflex response at spinal segmental level to stretch
of the bladder wall when the volume pressure reaches its physiological threshold and
provokes the desire to void and thus initiates micturition. The ways in which the expul
sive and closing forces perform their functions in the act of micturition have been the
subject of intensive studies. Barrington (1921), on account of animal experiments,
postulated six reflexes at hind-brain and spinal level involved in the act of micturition.
Van Duzen's (1935) concept based on Young
et al.
observations (1921, 1926) and his
own studies distinguishes three phases in the act of micturition:
1
Contraction of the trigone depressing the posterior portion of the internal vesical
orifice which is then opened.
2 A wave of detrusor contraction originating in the area of the internal vesical orifice,
extending towards the dome of the bladder and exerting a lateral pull on the internal
orifice which opens it further. (The effacement of the internal neck as a result of the
detrusor contraction due to its insertion into the area of the vesical neck has also been
confirmed by Lapides
et al.,
1960.)
3 Contraction of the abdominal muscles increasing the intra-abdominal pressure and
thus the expulsive power of the detrusor contraction. (Miillner (1951) found in fluoroscopic
studies that volitional voiding starts with increased abdominal pressure accompanied by
reciprocal relaxation of the pelvic floor.) This elicits a powerful pull on the vesical neck
initiating contraction of the bladder base spreading upwards and involving the whole
bladder musculature. Conversely, volitional interruption of micturition begins with
contraction of the pelvic floor muscles, resulting in elevation of the whole base of the
