Bladder Outlet Function  

1. Outlet Resistance

  • Identification:
    • VLPP used with video urodynamics:
      • visualization of the bladder neck during filling and emptying
      • useful since it is a dynamic test that mimics circumstances that cause incontinence
      • difficult to perform in children
      • totally incompetent outlet makes bladder evaluation more difficult due to leakage around the urodynamic catheter. In this case, occlusion of the bladder neck by the balloon of a Foley catheter may be useful to evaluate bladder function [Woodside 1982]
    • Urethral pressure profilometry
    • Sphincter EMG
    • Upright cystography:
      • demonstrates an open bladder outlet from the bladder neck to the distal sphincter mechanism
    • Cystoscopy
      • Provides supportive evidence by direct visual identification of the open bladder neck with bladder filling
    • Also refer to this
  • Classification of condition [Abrams 2002]:
    • Urethral function during filling
      • Normal urethral mechanism
      • Incompetent urethral closure mechanism
      • Urodynamic stress incontinence
    • Urethral function during voiding
      • Normal urethra function
      • Abnormal urethra function
        • Urethral overactivity [Abrams 2006]: Urethra contracting during voiding
          • Detrusor sphincter dyssnergia
          • Dysfunctional voiding
        • Non-relaxing urethral sphincter obstruction: Urethra failing to relax

2. Increased Outlet Resistance

  • Concept:
    • Kinesiologic disassociation of detrusor and sphincter that generally work in harmony.
    • Sphincter EMG activity that increases simultaneously with intravesical or detrusor pressure
    • True DSD exist only in patients who have an abnormality in pathways between the sacral spinal center and the pontine micturition center, generally caused by neurologic injury or disease
    • DSD can occur in the smooth muscle of the bladder neck and proximal urethra. But commonly ‘DSD’ refers to dyssynergia of the striated sphincter considering its clinical significance.
    • Abbreviation: DSD or DESD (Detrusor External Sphincter Dyssnergia)
  • Detection
    • Identified by the CMG and a simultaneous sphincter EMG or fluoroscopic visualization.
    • Criteria to define increased outlet resistance: currently not well defined
  • Types of condition: [Abrams 2006]
    • Detrusor sphincter dyssnergia (DSD):
      • seen only in patients with neurological disease and most classically in high level SCI.
      • Also refer to this
    • Dysfunctional voiding (Pseudodyssynergia): So called because during voiding attempts the sphincter does not relax. Originally this was thought to be behavioral, but the description of Fowler’s syndrome has proven that this can be a true neural syndrome in patients without SCI/D
      • similar urodynamic pattern as DSD
      • Sphincter EMG activity increases simultaneously with detrusor pressure. This prevents normal voiding in Fowlers syndrome, or dysfunctional voiding in children a learned phenomenon
      • typically seen in children who are neurologically normal
      • Causes:
        • pelvic floor muscle overactivity rather than to intrinsic striated muscle as in DSD
        • abdominal straining to either initiate or augment a bladder contraction
        • attempted inhibition of a bladder contraction either because of its involuntary nature or because of discomfort [Rudy 1993]
    • Non-relaxing urethral sphincter obstruction:
      • seen in classical form in meningomyelocele patients.
      • Failure of urethral relaxation rather than urethral contractions during attempted micturition

  • Clinical significance:
    • DSD causes a functional obstruction with resultant poor emptying and high detrusor pressure.
    • Over 50% of men with DESD, if untreated, significant complications (VUR, hydronephrosis, urolithiasis, or urosepsis) can ensue [Chancellor 1995].
    • Significant efforts have been made to treat DSD (
  • Other comments:
    • Its significance to the upper tract damage is well described by McGuire [McGuire 1981] (
    • No significant association between the specific level of injury and the DSD type [Weld 2000]
    • The presence of DSD is associated with complete injuries, elevated intravesical pressures [Weld 2000]
    • DSD vary with severity: worse in
      • continuous DSD> intermittent DSD
      • complete lesions > incomplete lesions
      • male> female

3. Decreased Outlet Resistance: Incompetent urethral closure mechanism

  • Concepts:
    • Frequent coexistent outlet incompetence in patients with myelodysplasia or exstrophy-epispadias complex
    • Criteria to define insufficient outlet resistance: an open bladder outlet on fluoroscopy, striated sphincter denervation, and/or an outlet resistance of less than 30cmH2O [Kryger 2000]
    • Frequently misleading especially in low compliance bladder because detrusor overactivity may open the bladder neck and make it appear incompetent [Kreder 1992]. Therefore, decisions regarding outlet function should be based on clinical, urodynamic, radiographic findings [Gonzalez 1985]
  • Detection [McGuire 2002]
    • Fluoroscopic urodynamic study (Green’s type III urinary incontinence):
      • Open bladder neck and nonfunctional proximal urethra anatomy at rest or
      • A urethra that leaks at a low VLPP
    • UPP study (Intrinsic sphincter dysfunction):
      • Low MUCP (<20cmH2O)
      • Probably ISD and type III SUI are different conditions.
  • Clinical situations (Oh 2006]:
    • Prototypical neuropathic urethral dysfunction occurs in patients (about 85%) with myelodysplasia. The bladder is decentralized and the proximal urethra non-functional. [VIDEO]
    • Patients with T12-L1 SCI (damage in the sympathetic outflow) also show identical loss of proximal urethral closing function.
    • Urethral damage caused by chronic catheterization in neurogenic bladder dysfunction often leads to loss of urethral function and very severe incontinence.
    • Patients with decreased outlet resistance may have less chance for the kidney damage but, instead, experience severe incontinence (stress incontinence or total incontinence) which greatly impact on the quality of life of the sufferers.
  • Other comments:
    • Simultaneous or sequential reconstruction of the bladder and outlet: controversial.
      • Difficulty in assessing the bladder and bladder outlet when one or both are compromised.
      • Outlet procedure (artificial sphincter or sling) may change in bladder behavior (become overactive) in response to the outlet manipulation [McGuire 1989].
Key Points of This Section
  • DSD is the result of loss of the brain stem centers influences on sacral cord function.
  • Fowlers syndrome and dysfunctional voiding in children are conditions similar to DSD but are not nearly as dangerous.
  • Loss of sacral cord and or root function associated with lower motor neuron lesions, myelodysplasia, results in fixed outlet resistance which determines the detrusor pressure at the instant of leakage. If this is 40 cms or more upper tract deterioration can be expected to develop.
  • An open non functional internal sphincter occurs in patients with lumbosacral myelodysplasia, and in patients with T12-L1, 2 level injuries. The radiographic appearance is similar to DSD but the mechanism is completely different.

 

References

  • Abrams P, Cardozo L, Fall M, Griffiths D, Rosier P, Ulmsten U, van Kerrebroeck P, Victor A, Wein A; Standardisation Sub-committee of the International Continence Society. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn. 2002;21(2):167-78.
  • Abrams P. Urodynamic techniques. In: Abrams P. Urodynamics, 3rd ed. Springer-Verlag, London 2006;17-116.
  • Chancellor MB, Rivas DA: Current management of detrusor-sphincter dyssynergia. In: McGuire EJ (editor): Advances in Urology. St. Louis, CV Mosby, 1995, pp 291–324.
  • Gonzalez R, Sidi AA. Preoperative prediction of continence after enterocystoplasty or undiversion in children with neurogenic bladder. J Urol. 1985 Oct;134(4):705-7.
  • Kreder KJ, Webster GD. Management of the bladder outlet in patients requiring enterocystoplasty. J Urol. 1992 Jan;147(1):38-41.
  • Kryger JV, Gonzalez R, Barthold JS. Surgical management of urinary incontinence in children with neurogenic sphincteric incompetence. J Urol. 2000 Jan;163(1):256-63.
  • McGuire EJ, Woodside JR, Borden TA, Weiss RM. Prognostic value of urodynamic testing in myelodysplastic patients. J Urol. 1981 Aug;126(2):205-9.
  • McGuire EJ. Editorial comment. J Urol 1989; 142:301
  • McGuire EJ, Clemens JQ. Pubovaginal sling. In: Walsh PC, Retik AB, Vaughan Jr, ED, Wein AJ, Kavoussi LR, Novick AC, Partin AW, Peters CA (editors). Campbell’s Urology 8th ed. Philadelphia 2002;1151-71.
  • Oh SJ, Stoffel JT, McGuire EJ. Pubovaginal sling. In: Campbell-Walsh’s Urology, 9th edition, Saunders, Philadelphia, 2006 (in press)
  • Rink RC. Mitchell ME. Surgical correction of urinary incontinence. J Pediatr Surg 19:637, 1984.]
  • Rudy DC. Detrusor-external sphincter dyssynergia. Prob Urol 1993;7:68–93.
  • Weld KJ, Graney MJ, Dmochowski RR. Clinical significance of detrusor sphincter dyssynergia type in patients with post-traumatic spinal cord injury. Urology. 2000 Oct 1;56(4):565-8.
  • Woodside JR, McGuire EJ. Technique for detection of detrusor hypertonia in the presence of urethral sphincteric incompetence. J Urol. 1982 Apr;127(4):740-3.

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