Urodynamics Flashcards
What is max and min urine production rate and when would it occur?
- Min is around 1ml/min (max ADH/AVP secretion)
- Max is around 20ml/min (min ADH/AVP secretion)
What is normal capacity of a bladder?
400-600ml
What muscle is in bladder wall and why?
Smooth muscle (detrusor muscle) Smooth muscle allows large volume changes
What affects activity of detrusor muscles?
Is affected by reflexes.
Passive stretch of the wall triggers contractions
What does contraction of detrusor produce?
Additional force/pressure
What innervates the bladder?
- Sympathetic; from L1, L2 (bladder wall and internal sphincter)
- Parasympathetic; from S2, S3, S4 (bladder wall)
- Somatic; from S2, S3, S4 (sensory and motor to external sphincter)
Describe how bladder is controlled (afferents and efferents)?
Afferents:
1. Sensory fibres sense the stretch of the bladder wall. These afferents run in the hypogastric nerve and enter cord in the upper lumbar roots.
2. Other sensors near the urethra sense flow of urine
3.Skeletal muscle sensors in the external sphincter
Efferents:
1.Parasympathetic to detrusor
2.Sympathetic to internal sphincter
3.Somatic to external sphincter
Compare male and female external sphincter?
- Males; strong external sphincter. Skeletal muscle
- Females; weaker external sphincter. Less skeletal muscle.
What technique can be used to investigate bladder?
- Multi barrel catheter inserted through urethra
- Allows fluid to fill the bladder at a controlled rate
- Allows pressure to be measured at several sites simultaneously: bladder, sphincter etc.
- Some devices allow recording of sphincter muscle activity.
How are catheters used?
- Place 1 opening in the bladder to allow direct filling and measure bladder pressure.
- Inflate baloon to close off urethra
- Position 2nd opening in the urethra to measure the sphincter pressure
- Then fill the bladder and record the pressure to establish bladder compliance.
- As bladder fills, watch for signs of bladder wall contraction and sphincter contraction.
Describe the storage phase?
- Early filling phase, low pressure in bladder, bladder wall and external sphincter relaxed.
- No flow in urethra: urethral pressure higher than bladder pressure.
- Sensations develop, then sphincter contracts to maintain continence.
Describe voluntary control and reflexes of bladder control in storage phase?
- Sympathetic effects dominate during bladder filling
- Fibres in the hypogastric nerve supress contraction of the detrusor
- Somatic fibres in the pudendal nerve control the external sphincter.
Describe the voiding phase?
- Urge, then voluntary voiding.
- Bladder contracts, urethra and sphincter relaxes
Flow in urethra: bladder pressure more than urethral pressure. - Voluntary stop flow then a 2nd voiding phase.
Describe voluntary control and reflexes of bladder control in voiding phase?
- Parasympathetic actions dominate during emptying
- Fibres in the pelvic splanchnic nerve cause the detrusor to contract.
What are the typical volumes and pressures for adults in the storage and voiding phase?
- Storage:
- lower pressures, volumes: relate to urine production rate
- Voiding:
- higher pressures, flow rates relate to emptying times
Describe complex co-ordination?
- External sphincter is skeletal muscle which changes force faster.
- Urethra is smooth muscle which changes force slower.
- Smooth muscle and bladder wall contracts
- Smooth muscle in urethra relaxes
What are the sensations which accompany filling?
- No sensation then a sense of filling
- Then fullness, then desire
- Then discomfort and pain
- Sensations depend on the rate of filling
What supports sensations of bladder?
Sensations are supported by larger myelinated fibres and small unmyelinated fibres
Small fibres probably linked to unpleasant sensations
What is normal volume/pressure relationship and some possible defects of this?
Fills slowly to around 375ml, then reflex contractions start, then stop.
- Neurogenic bladder; contraction starts at lower volume
- Atonic bladder; pressure rises slowly as bladder fills
When may flow rated be reduced?
If urethra is narrowed, flow rate is reduced.
Time of flow is increased.
Volume voided may be reduced, leading to increased frequency of voiding.
What are the effects of BPH?
- Urethra passes through prostate gland
- With age there is likely to be hypertrophy of prostate
- This can compress the urethra and slow flow of urine
- This can prevent full emptying and lead to more frequent voiding.
How is bladder reflex controlled?
- Via centres in the sacral cord in the pons
- Pontine centres co-ordinate with higher centres
What are some components of the bladder?
- Ureter
- Transitional epithelium
- Detrusor muscle
- Trigone
- Internal urethral sphincter
- External urethral sphincter
- Urethra
- Bladder neck
When does bladder fill and empty with relation to vesicle pressure?
-Bladder fills when sphincter pressures or urethra pressures is more than vesicle pressures.
No flow out.
-Bladder empties when vesicle pressure is more than sphincter pressures or urethra pressures.
Fluid pushes past sphincter to escape.
