Urodynamics

Question 1

What is max and min urine production rate and when would it occur?

Answer 1

• Min is around 1ml/min (max ADH/AVP secretion)

- Max is around 20ml/min (min ADH/AVP secretion)

Question 2

What is normal capacity of a bladder?

Answer 2

400-600ml

Question 3

What muscle is in bladder wall and why?

Answer 3

Smooth muscle (detrusor muscle)
Smooth muscle allows large volume changes

Question 4

What affects activity of detrusor muscles?

Answer 4

Is affected by reflexes.

Passive stretch of the wall triggers contractions

Question 5

What does contraction of detrusor produce?

Answer 5

Additional force/pressure

Question 6

What innervates the bladder?

Answer 6

• 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)

Question 7

Describe how bladder is controlled (afferents and efferents)?

Answer 7

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

Question 8

Compare male and female external sphincter?

Answer 8

• Males; strong external sphincter. Skeletal muscle

- Females; weaker external sphincter. Less skeletal muscle.

Question 9

What technique can be used to investigate bladder?

Answer 9

• 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.

Question 10

How are catheters used?

Answer 10

1. Place 1 opening in the bladder to allow direct filling and measure bladder pressure.
2. Inflate baloon to close off urethra
3. Position 2nd opening in the urethra to measure the sphincter pressure
4. Then fill the bladder and record the pressure to establish bladder compliance.
5. As bladder fills, watch for signs of bladder wall contraction and sphincter contraction.

Question 11

Describe the storage phase?

Answer 11

1. Early filling phase, low pressure in bladder, bladder wall and external sphincter relaxed.
2. No flow in urethra: urethral pressure higher than bladder pressure.
3. Sensations develop, then sphincter contracts to maintain continence.

Question 12

Describe voluntary control and reflexes of bladder control in storage phase?

Answer 12

• 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.

Question 13

Describe the voiding phase?

Answer 13

1. Urge, then voluntary voiding.
2. Bladder contracts, urethra and sphincter relaxes
   Flow in urethra: bladder pressure more than urethral pressure.
3. Voluntary stop flow then a 2nd voiding phase.

Question 14

Describe voluntary control and reflexes of bladder control in voiding phase?

Answer 14

• Parasympathetic actions dominate during emptying

- Fibres in the pelvic splanchnic nerve cause the detrusor to contract.

Question 15

What are the typical volumes and pressures for adults in the storage and voiding phase?

Answer 15

• Storage:
• lower pressures, volumes: relate to urine production rate
• Voiding:
• higher pressures, flow rates relate to emptying times

Question 16

Describe complex co-ordination?

Answer 16

• 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

Question 17

What are the sensations which accompany filling?

Answer 17

• No sensation then a sense of filling
• Then fullness, then desire
• Then discomfort and pain
• Sensations depend on the rate of filling

Question 18

What supports sensations of bladder?

Answer 18

Sensations are supported by larger myelinated fibres and small unmyelinated fibres
Small fibres probably linked to unpleasant sensations

Question 19

What is normal volume/pressure relationship and some possible defects of this?

Answer 19

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

Question 20

When may flow rated be reduced?

Answer 20

If urethra is narrowed, flow rate is reduced.
Time of flow is increased.
Volume voided may be reduced, leading to increased frequency of voiding.

Question 21

What are the effects of BPH?

Answer 21

• 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.

Question 22

How is bladder reflex controlled?

Answer 22

• Via centres in the sacral cord in the pons

- Pontine centres co-ordinate with higher centres

Question 23

What are some components of the bladder?

Answer 23

• Ureter
• Transitional epithelium
• Detrusor muscle
• Trigone
• Internal urethral sphincter
• External urethral sphincter
• Urethra
• Bladder neck

Question 24

When does bladder fill and empty with relation to vesicle pressure?

Answer 24

-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.