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Urodynamics and bladder management details

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  • Urodynamics and bladder management details

    I have urodynamics scheduled this Thursday. So I wanted to educate myself about urodynamics and SCI bladder management in general, to be prepared. Here is what I compiled from a Google Scholar searched web site (link below) and our own CareCure postings. Thanks a millions to SCI-Nurse and other members whose postings I have used. SCI-Nurse and others, could you please check and see if everything makes sense. And if there is a need to add something to make it more useful, please do so. Thanks, and hope others find it useful.


    Urodynamics Details

    • Filling cystometry consists of measuring bladder pressure as the bladder is filled to capacity with the patient lying down. A 'volume versus pressure' graph, which called a cystometrogram (CMG), is produced.

    • The cystometrogram is basically performed to evaluate the compliance and stability of the detrusor muscle.

    • Compliance is simply the elastic property of the detrusor muscles. An evaluation of compliance is an evaluation of the ability of the bladder to 'stretch' to 'normal' capacity while maintaining low pressures.

    • Stability is evaluated by observing the detrusor while filling the bladder to normal capacity. The evaluation determines the presence or absence of detrusor overactivity (or instability).

    • A bladder with normal compliance will demonstrate no greater than 15cm water increase in detrusor pressure as it progresses from empty to capacity during a CMG.

    The detrusor pressure is a subtracted pressure that is calculated by subtracting the abdominal pressure from the vesical pressure.

    Vesical pressure is the pressure that is measured inside the bladder, with a catheter that is specifically designed for pressure monitoring in the urinary tract. This is a combination of the pressure being exerted on the bladder by the abdominal contents, the weight or pressure of any urine in the bladder and the force that the detrusor muscle is exerting on that fluid. The pressure in an empty bladder is usually called resting pressure, which changes with position. The normal bladder resting pressures vary between 8 and 40cm of water (ie the pressure exerted at the bottom of a column of water 40cm high), depending upon the particular patient and position during study.

    Abdominal pressure is measured by placing a special catheter either in the rectum or the vagina.

    • For a patient to remain dry, the pressures in the urethra must remain greater than the pressure in the bladder, during filling. The average urethral closure pressure for a female is 60cmH20 and for a male it is 80cmH20.

    • Flow/pressure study is usually performed immediately after filling cystometry. The urethral catheter is narrow enough that voiding can occur around it. The important measurement from the study is the detrusor pressure at maximum flow. By this method, obstruction to passage of urine (high pressure, low flow) can be distinguished from a lack of tone in the detrusor muscle (low pressure, low flow).

    High Bladder Pressure

    • If a full bladder has a high pressure (generally considered anything over 40 cm H2O), this can result in urine being pushed back up the ureters (connection between kidneys and bladder); this is known as urinary reflux. A KUB can identify reflux into the kidneys.

    • Detrol and Ditropan are anticholinergic drugs used to reduce bladder pressure and/or increased bladder capacity. They work on the bladder muscle to relax it as it is innervated by the parasympathetic nerves. The long acting anticholinergic work better for some, but are less effective for others. Combining anticholinergic med with imipramine can make it more effective.

    • Dysynergia is one cause of high pressure bladder, but not the only one. Uninhibited tone in the bladder is one cause, as well as the increased level of connective tissue (collegen) which forms in the bladder after denervation. Both those with spastic and those with flaccid bladders can develop high pressures with time. This is one reason why urodynamics should be done every 2 years or so for anyone who does not have an indwelling catheter or a urinary diversion.

    • Thickening, or trabeculation of the bladder wall indicates that the bladder is trying to contract against a lot of resistance (a tight sphincter) and is probably doing so with high pressures. The thickening itself is not too concerning although it can lead to diverticuli (out-pouchings of the bladder wall that can collect stagnant urine and increase UTI risks) but what causes it can be very concerning (high pressures).

    Detrusor Sphincter Dyssynergia (DSD)

    • The bladder should normally hold about 300-400cc when cathed. If there is leaking or reduced capacity, the bladder and sphincter may be having some spasticity, which can lead to dyssynergia, i.e. bladder tries to contract to empty, but the sphincter will not open to allow the urine to pass.

    • There are two urethral sphincters, internal and external. Internal is of the smooth muscle (cell type) type and is usually not the problem post SCI; external is of the skeletal muscle type and gets spastic post SCI just like skeletal muscle elsewhere (legs/arms) in our body. We cannot relax it when we need to with the result being inability to empty fully and safely at low bladder pressures.

    • The only way to diagnose if you have either internal or external sphincter dysynergia is to do urodynamics that include fluoroscopy (called videourodynamics or VUD) so that the sphincters can be visualized during the study. Sometimes a voiding cystogram will also show this if done with videofluoscopy.

    • Flomax and other alpha sympathetic blockers like Hytrin, Minipress, Cardura, or Dibenzyline only help with internal sphincter dysynergia (the sphincter getting tighter when the bladder contracts). Even for internal sphincter dysynergia, alpha blockers are successful only about 50% of the time.

    • The external sphincter is striated muscle and is innervated by somatic nerves, not by the autonomic nervous system. It is not relaxed by either the alpha sympathetic blockers or by the anticholinergic drugs. It may be somewhat relaxed by using drugs for skeletal muscle spasticity such as Baclofen or Zanaflex, but this can also lead to leakage between caths as this is the primary muscle of continence.

    • Surgical intervention can be used for both, internal or external sphincter dysynergia: a bladder neck resection for the internal, and sphincterotomy or urethral stent for the external, but of course these will result in continuous urine leakage and the need to wear an external catheter continuously. Not recommended for females due to this (and these conditions are relatively rare in females).

    Urinary Retention

    • Elavil is a medication that is often used for its anticholinergic side effects to deliberately cause urinary retention in those who do intermittent cath. It increases bladder capacity, decreases pressure and decreases leakage. Use of any of the tricyclic antidepressants will have the same effect. This is why these drugs are not recommended for those who use an external condom catheter (unless they plan to change to intermittent cath) or for AB men with enlarged prostates, as it can also cause them to develop retention.

    • Urocholine, which was occasionally used for urinary retention has the opposite effect of the Elavil. It is designed to make the bladder contract sooner and harder when trying to void. It can have many serious side effects, and it was found that while it might make a person urinate, it often did so with such high pressures that it was unsafe from the standpoint of our current knowledge about voiding with high pressures. It is rarely if every appropriately used in SCI anymore.

    Problems with Intermittent Cathing

    • If you are having a hard time passing a catheter past the external sphincter (which spasms in response to a foreign object being introduced), use the following procedure. First be sure you have lubricated the first 6-8 inches of the catheter very well. When you reach the place of resistance, do not poke or jab with the catheter. Do not force it. Maintain firm but gentle pressure with the catheter for 1-2 minutes. This will fatigue the sphincter, and it will relax. When it does, you can feel it, and slide the catheter on through.

    • If this does not work, you may have a urethral false passage or stricture. Your urologist may want to do a urethrogram to rule this out. If nothing is found, then you may want to try a lubricious (pre-lubricated) catheter using the same procedure as above. These catheters are more expensive and are not re-usable.

    • Sometimes Coude tipped catheters are prescribed for this problem, but they really are only appropriately used for men with enlarged prostates, and if used incorrectly can actually damage both the urethra and sphincter.

  • #2
    This is an excellent review of information regarding bladder conditions and answers all of my questions about these conditions.



    • #3
      A nice summary! Urodynamics can get quite complex and is very individualized.They are the experts.
      I recommend you go, get tested, and research the results of what they tell you.

      Xylocaine gel is also used on some men when cathing if they perceive "pain" and tighten the sphincter.

      The SCI-Nurses are advanced practice nurses specializing in SCI/D care. They are available to answer questions, provide education, and make suggestions which you should always discuss with your physician/primary health care provider before implementing. Medical diagnosis is not provided, nor do the SCI-Nurses provide nursing or medical care through their responses on the CareCure forums.


      • #4
        Thank you mike and SCI-Nurse. My urodynamics appointment got canceled and will be rescheduled later because of doctor's change of program. I'm looking forward to find out about my bladder.