The neuropathic urethra

Abstract

Abstract. The hypothesis is advanced that the functional urethral obstruction found in neuropathic states is due, in part at least, to urethral supersensitivity following sym pathetic decentralisation.A simple postural test for this condition is described. By its use it has been shown that urethral denervation occurs not only in disorders of the central nervous system but with peripheral damage such as may result from rectal excision and hysterectomy.In some cases with functional urethral obstruction, attributable to supersensitivity of the urethra, no neurological abnormality has been found. These may be examples of localised visceral neuropathy.Key words: Neuropathic urethra; Urethral supersensitivity test; Urethral obstruction.BLADDER function reflects the relationship between intravesical pressure and urethral resistance. In disorders of the nervous system poor bladder emptying is more often due to urethral obstruction than to subnormal voiding pressures. The bladder, however, was almost exclusively the focus of attention in these cases until less than 50 years ago. Then Watkins (1936) reported finding obstruction at the level of the membranous urethra in patients with lesions of the sacral segments. Internal membranous urethrotomy (loosely called 'external sphincterotomy') was introduced for the relief of these cases (Ross et ai., 1957), and whilst it proved effective, the mechanism of the obstruction was obscure (Gibbon, 1973).About the same time Emmett et ai. (1948) noted the common occurrence of membranous urethral obstruction in spastic paraplegics and suggested its relief by subarachnoid alcohol block, sacral rhizotomy or pudendal neurectomy on the assumption that contraction of the striated muscle of the urethra or pelvic floor was responsible. Electromyography has given some support to this concept (Diokno et al., 1974). Rhizotomy, whether chemical or surgical, gave effective relief and the accompanying loss of reflex bladder activity could be compensated for, except in cervical lesions, by abdominal straining or manual compression. Unfortunately, the inevitable impotence produced by sacral rhizotomy was unacceptable to many patients, and pudendal neurectomy as an alternative therefore had a vogue. This operation proved unreliable, however, which is not surprising in view of the repeated demonstration that the internal pudendal nerves do not supply the external urethral sphincter (Gil-Vernet, 1964; Donker et ai., 1976). On the other hand, impotence was an unexpectedly common complication and one which has not even yet been adequately explained. Iilternal membranous urethrotomy, aimed at dividing the striated urethral sphincter, has now become firmly established as the procedure of choice for these cases (Ross et ai., 1976) as well as for the sacral segment cases for whom the operation was originally described.The mechanism of neuropathic urethral obstruction, particularly in conus 222PARAPLEGIA lesions, has been the subject of research at Southport for the past 30 years. An obvious clue was the trad...

Bladder Dysfunction after Simple Hysterectomy: Urodynamic and Neurological Evaluation

“…This is supported by evidence that detrusor instability, urethral obstruction, stress incontinence, and bladder acontractility may all occur following damage to the pelvic plexus [Bradley and Andersen, 1977;Gibbon et al, 1980;Snooks and Swash, 1984;Anderson, 1984;Restorick and Mundy, 1989].…”

“…Why this opera tion seems to have a protective effect on the bladder was unexplained. Several factors have been implicated in the aetiology of the urinary symptoms, including: removal of the bladder supports with trigonal displacement [Han ley, 1969]; vaginal shortening [Hanley, 1969]; post-cli macteric changes, and pelvic nerve damage [Rankin, 1969], Gibbon et al [1980] noted the presence of functional urethral obstruction in two thirds of a population of women who had had a hysterectomy, and suggested that this was a result of a specific urethral neuropathy.…”

Assessment of Congenital Neurovesical Dysfunction by Combined Urodynamic and Radiological Studies

“…The investigation was therefore designed to reproduce, as far as possible, the normal performance of the bladder, and essential features of the method included avoidance of preliminary drainage of residual urine, slow filling rates (not exceeding 10 ml/min) and continuation until a consistent pattern of filling and voiding was obtained. One major difficulty was that in the majority of patients, paralysis necessitated a supine examination, and quite apart from the effects that changes in posture may have on the behaviour of the bladder and urethral musculature (Gibbon et al, 1980), this may easily lead to an underestimation of SWI unless a systematic attempt is made to disclose it by periodic straining or application of suprapubic pressure as the bladder fills.…”

“…It is generally agreed that the former is due to somatically mediated dyssynergic contraction of the striated component of the distal urethral sphincter and pelvic floor occurring as part of a mass pelvic reflex. None of the several theories advanced to explain isolated distal sphincter obstruction is entirely convincing (Johnston and Farkas, 1975;Krane and Siroky, 1979) and this is in part due to the uncertainty which presently surrounds the anatomy and innervation of the smooth muscle component of the bladder neck and proximal urethra (El Badawi and Schenk, 1974;Gosling et al, 1977;Koyanagi, 1979;Gibbon et al, 1980). Clinically, our experience accords with that of Hachen (1980), that alphaadrenolytic therapy has little or no effect on detrusor/sphincter dyssynergia but often reduces outlet resistance when there is isolated distal sphincter obstruction.…”

Intrinsic neuromuscular defects in the neurogenic bladder: V. Autonomic re‐innervation of the male feline rhabdosphincter following somatic denervation by bilateral sacral ventral rhizotomy

“…The more recent urologic literature confirms that urethral "obstruction" at the level of the rhabdosphincter may occur in some cases of the lower-motor neurogenic bladder. Such "obstruction" may be explained by (1) angulation of the membranous urethra against the "perineal membrane" as the bladder and prostate are prolapsed downward between the flaccid denervated levatores ani [Vincent, 1966;Dollfus et al, 19721 ; (2) supersensitivity-related catecholaminergic contraction of the circular urethral smooth muscularis in the region of the striated sphincter [Gibbon, 1978;Sunder et al, 1978;Parsons and Turton, 19801; (3) activation or spasmodic contraction of myofibers of a somatically denervated rhabdosphincter by probably sympathogenic impulse propagation from its anatomically intimately associated smooth musculature of the distal urethral wall [ Bors and Comarr, 1971;Koyanagi et al, 19821;(4) urethral narrowing by fibrotic atrophy of the somatically denervated striated sphincter [Bauer et al, 1977;Mondell et al, 19801, or (5) the possible occurrence, within the clinical setting of a lower-motor vesicourethral smooth muscle dysfunction, of an uppermotor neuron type hyperactivity or involuntary contraction of the striated sphincter [Blaivas, 19821. Although the first explanation may be valid to some extent, it has been shown that significant resistance in the distal sphincteric region may be preserved following radical extirpative pelvic surgery (eg , abdominoperineal rectal resection) despite the unavoidable resultant anatomic distortion of the urethra, if only parasympathetic or both parasympathetic and pudendal neural pathways to the bladder and urethra are injured, but their sympathetic pathways remain largely intact [McGuire and Wagner, 1977;Blaivas and Barbalias, 19831. The Second explanation appears to be unlikely since the urethral smooth muscle proximal to and in the region of the rhabdosphincter are integral parts of the same smooth muscle unit of micturition (the vesicourethral lissosphincter) in all mammalian species so far studied, including man, being in direct anatomical continuity, having the same histologic structure, and being supplied by the same source of dual cholinergidadrenergic innervation with an idential intensity and intrinsic distribution pattern of the two types of autonomic nerves, both histochemically and ultrastructurally [Elbadawi, 1982bl. Such identical identity of the urethral smooth muscularis proximal to and in the rhabdosphincteric region appears to be borne out by some recent pharmacologic studies on the "neurogenic urethra" [Nordling, 1978;Koyanagi et al, 19821.…”