This document provides an overview of urodynamics, including the physiology of micturition, urodynamics equipment, cystometry, uroflowmetry, pressure flow studies, and abnormal findings. Key points include: 1. Urodynamics evaluates bladder filling, storage, and emptying through tests like cystometry, uroflowmetry, and pressure flow studies. 2. Cystometry measures bladder pressure during filling and identifies abnormalities like impaired compliance, detrusor overactivity, and high leak point pressures. 3. Pressure flow studies quantify voiding and help differentiate obstruction from poor contractility. 4. Abnormal findings on urodynamics like high pressures, impaired compliance,

1. Gaurav Nahar
DNB Urology Resident,
MMHRC, Madurai
URODYNAMICS

3. NORMAL LUT TWO-PHASE
FUNCTION: Storage & Voiding

4. Physiology of Micturition
• LUT innervation:
Somatic, parasympathetic (PNS) &
sympathetic (SNS)
• As urine fills the bladder, detrusor stretches
and allows bladder to expand.
• ~300 ml in bladder before the brain
recognizes bladder fullness.

5. Physiology of Micturition

6. Physiology of Micturition
• Low bladder volumes: SNS is stimulated and
PNS is inhibited.
• Bladder full: PNS stimulated (bladder
contracts) SNS inhibited (internal sphincter
relaxes).
• Intravesical pressure > resistance within the
urethra: urine flows.
• Pudendal nerve innervates external sphincter.

7. Anatomy of bladder & its outlet

9. URODYNAMICS

10. • Dynamic study of transport, storage &
evacuation of urine.
• Main goal of UDS: to reproduce pt.'s
symptoms and determine their cause by
various tests.

11. UDS Armamentarium
• Cystometry(most important test), filling
cystometry & voiding cystometry
• Uroflowmetry
• Urethral pressure studies
• Pressure flow micturition studies
• Video-urodynamic studies
• Electromyography

12. INDICATIONS
• Incontinence:
-recurrent incontinence in whom surgery is
planned.
-mixed urge & stress symptoms.
-associated voiding problems.
-pts. with neurologic disorders.
-pts. with mismatch between signs and
symptoms.

13. INDICATIONS (contd..)
• Outflow Obstruction:
-pt with LUTS, at least uroflow study.
• Neurogenic bladder:
-all neurologically impaired patients with
neurogenic bladder dysfunction.
• Children with voiding dysfunction:
-kids with daytime urgency and urge incontinence,
recurrent infection, reflux, or upper tract changes.

14. Clinical role
• Characterization of detrusor function.
• Evaluation of bladder outlet.
• Evaluation of voiding function.
• Diagnosis and characterization of
neuropathy.

15. Three important rules before starting
UDS evaluation:
• 1. Decide on questions to be answered before
starting a study.
• 2. Design the study to answer these
questions.
• 3. Customize the study as necessary.

16. CYSTOMETRY
• Measurement of intravesical bladder pressure
during bladder filling(measures volume-pressure
relationships).
• Used to assess bladder sensation, capacity,
compliance, detrusor activity.
• Bladder access by transurethral catheter, or rarely
by percutaneous suprapubic tube.
• Filling medium either gas (CO2) or liquid (water,
saline, or contrast material at body temp).
• Liquid cystometry is more physiologic.
• Ideally, filling should be performed in standing
position.

17. CYSTOMETRY(contd...)
• Bladder filling either by diuresis or filling through a
catheter.
• Filling
– slow (up to 10 ml/min), physiologic
– medium (10 to 100 ml/min)
– fast (> 100 ml/min)
• Children and pts with known bladder hyperactivity require
slow fill rates.
• Reference point:- superior edge of symphysis pubis.
• All systems should be zeroed to atmospheric pressure.
• No air bubbles.

18. Phases of cystometrogram

19. • Normal CMG:
- Capacity 350-600ml
- First desire to void
between 150- 200 ml.
- Constant low pressure that
does not reach more than
6-10 cm H2O above
baseline at the end of
filling.
- Provocative
maneuvers(cough, fast fill
etc.) should not provoke a
bladder contraction
normally.
- Absence of systolic
detrusor contractions.
- No leakage on coughing .
- A voiding detrusor
pressure rise of < 70 cm
H2O with a peak flow rate
of > 15 ml / s for a volume
> 150 ml.
- Residual urine of < 50 ml.

20. CYSTOMETRY(contd...)
• Single Vs multi-channel UDS:
-single: Pves only
-multi: Pves, Pdet, Pabd

21. CMG PARAMETERS
• Intravesical pressure(Pves): Total Pressure within
the bladder.
• Abdominal pressure(Pabd): Pressure surrounding the
bladder; currently estimated from rectal, vaginal, or
extraperitoneal pressure or a bowel stoma.
• Detrusor pressure(Pdet): Component of intravesical
pressure created by forces on the bladder wall, both
passive and active.
• True detrusor pressure = Intravesical pressure -
Intraabdominal pressure.(Pdet = Pves-Pabd)

22. • Physiologic filling rate: A filling rate < predicted
maximum. Predicted maximum = body weight in kg divided
by 4 and expressed as ml/min.
• Nonphysiologic filling rate: A filling rate > predicted
maximum.
• First sensation of bladder filling: Volume at which patient
first becomes aware of bladder filling.
• First desire to void: Feeling during filling cystometry that
would lead the patient to pass urine at the next convenient
moment.
• Strong desire to void: Persistent desire to void without fear
of leakage.

23. • Compliance:
- Relationship between change in bladder volume
and change in Pdet (Δvolume/Δpressure); measured
in ml/cm H2O.
- Normal bladder is highly compliant, and can hold
large volumes at low pressure.
- Normal pressure rise during the course of CMG in
normal bladder will be only 6-10 cm H2O.
- Decrease compliance < 20 ml/cm H2O, poorly
distensible bladder.

24. Impaired compliance is seen in:
• neurologic conditions: spinal cord injury/lesion,
spina bifida, usually results from increased outlet
resistance (e.g., detrusor external sphincter
dyssynergia [DESD]) or decentralization in the
case of lower motor neuron lesions,
• Long-term BOO (e.g., from benign prostatic
obstruction),
• Structural changes- radiation cystitis or
tuberculosis.
• Impaired compliance with prolonged elevated
storage pressures is a urodynamic risk factor and
needs treatment to prevent renal damage.

25. • Urgency: A sudden compelling desire to void.
• Normal detrusor function: Allows bladder filling
with little or no change in pressure, no involuntary
contractions.
• Detrusor overactivity: Involuntary detrusor
contractions during the filling phase, spontaneous
or provoked.
• Storage greater than 40 cm H2O is associated
with harmful effects on the upper tract.
• Overactive bladder: storage symptoms of urgency
with or without urgency incontinence, usually with
frequency and nocturia.

27. • Neurogenic detrusor overactivity: Overactivity
accompanied by a neurologic condition; also k/a
detrusor hyperreflexia.
• Idiopathic detrusor overactivity: Detrusor
overactivity without concurrent neurologic cause; also
k/a detrusor instability.

28. • Abdominal leak point pressure(ALPP):
Intravesical pressure at which urine leakage occurs
because of increased abdominal pressure in the
absence of a detrusor contraction.
• ALPP is a measure of sphincteric strength or
ability of the sphincter to resist changes in Pabd
• Applicable to stress incontinence; ALPP can be
demonstrated only in a patient with SUI.
• There is no normal ALPP, because patients without
stress incontinence will not leak at any physiologic
Pabd.
• Lower the ALPP, weaker is the sphincter.

29. – ALPP<60 cm H2O: significant ISD
– ALPP 60-90 cm H2O: equivocal
– ALPP>90 cm H2O: urethral
hypermobility; little or no ISD

30. • Detrusor leak point pressure(DLPP): Lowest
detrusor pressure at which urine leakage occurs in
the absence of either a detrusor contraction or
increased abdominal pressure (risk with > 40cm
H2O).
• Its a measure of Pdet in a patient with decreased
bladder compliance.
• Higher the urethral resistance, higher the DLPP, the
more likely is upper tract damage as intravesical
pressure is transferred to the kidneys.

32. UROFLOMETRY
• Non invasive study.
• Measurement of the rate of urine flow over time.
• Estimate of effectiveness of the act of voiding along with
PVR.
• Influenced by
– effectiveness of detrusor contraction
– completeness of sphincteric relaxation
– patency of the urethra
• 3 methods used
– gravimetric
– rotating disk
– electronic dipstick

33. Recorded variables during UFM study:
• Voided volume (VV in milliliters)
• Flow rate (Q in milliliters per second)
• Maximum flow rate (Qmax in milliliters per second)
• Average flow rate (Qave in milliliters per second)
• Voiding time (total time during micturition in seconds)
• Flow time (the time during which flow occurred in seconds)
• Time to maximum flow (onset of flow to Qmax in seconds)

34. • Optimal voids 200 to 400cc.
• Voids < 150cc are difficult to interpret.
• Pt. should be well hydrated with full bladder, but
not overly distended bladder.
• Should be performed in privacy and pt.encouraged
to void in his normal fashion.
• Qmax & shape of curve- more reliable indicators of
BOO.
• Qmax- most reliable variable in detecting abnormal
voiding.

35. Normal uroflow curve is bell-shaped

36. Flattened pattern: Obstruction

37. Interrupted or straining pattern: Impaired bladder
contractility, obstruction, or voiding with/by abdominal
straining.

38. "Box-pattern" : Urethral Stricture

39. Post Void Residual Urine
• Excellent assessment of bladder emptying.
• Performed by ultrasound (bladder scan) or
catheterization.
• Normally, it is < 0.5ml, but < 10% of voided
volume is considered insignificant.

40. Urethral pressure profilometry
• Urethral pressure profile (UPP): a graph
indicating intraluminal pressure along the
length of urethra.
• Urethral pressure: fluid pressure needed to
just open a closed urethra.
• UPP is obtained by withdrawal of a pressure
sensor (catheter) along the length of urethra.

41. UPP Parameters:
• Urethral closure pressure profile is given by subtraction of
intravesical pressure from urethral pressure.
• Maximum urethral pressure is highest pressure measured
along the UPP.
• Maximum urethral closure pressure (MUCP) : maximum
difference between urethral pressure and intravesical
pressure.
• Functional profile length: length of urethra along which
urethral pressure exceeds intravesical pressure in women.

42. • In most continent women,
functional urethral length:approx.3 cm &
MUCP is 40 to 60 cm H2O.
• MUCP is not always indicative of severity of
incontinence hence not used commonly.

43. UPP

44. PRESSURE FLOW
MICTURITION STUDIES
• Simultaneous measurement of bladder pressure and
flow rate throughout the micturition cycle.
• Best method of quantitatively analyzing voiding
function.
• Access to bladder via transurethral or SPC 8F or
less.
• Intra-abdominal pressure measured by balloon
catheter in rectum or vagina.
• Men should void in standing position, while
women seated on commode.

46. • Detrusor pressure at maximal flow(Pdet at Qmax):
Magnitude of micturition contraction at the time
when flow rate is at its maximum.
• Pressure <100 cm H2O indicate outlet obstruction
even if the flow rate is normal.
• Normal male generally voids with Pdet 40-60 cm
H2O and woman with lower pressure.
• Pdet more accurately measures bladder wall
contractions.

47. • Indications for pressure-flow studies:
- to differentiate between pts with a low Qmax sec.
to obstruction, from those sec.to poor contractility.
- Identify pt.with normal flow rates but high pressure
obstruction.
- LUTS in pt with hx of neurologic disease(CVA,
Parkinson’s).
- LUTS with normal flow rates (Qmax > 15cc/min).
younger men with LUTS.
- Men whom LUTS s/o bladder instability rather
than flow disorder.
- Men with little endoscopic evidence of prostate
occlusion

48. ICS provisional nomogram

49. VIDEO-URODYNAMICS
• UDS with simultaneous fluoroscopic image of
lower urinary tract.
• Equipment and technique:
- CMG + PFS same as before but the study is
conducted on a fluoroscopy table, and the filling
medium is a radiographic contrast agent.
• clinical applicability:
– complex BOO
– evaluation of VUR during storage &/or filling.
– neurogenic bladder dysfunction
– identification of associated pathology

50. • Primary BNO diagnosis & differentiation
from dysfunctional voiding in women: only
on VUDS.

51. Video-urodynamics

52. ELECTROMYOGRAPHY
(EMG)
• Study of the electric potentials produced by depolarization
of muscle membranes.
• In case of UDS, EMG measurement of striated sphincteric
muscles of the perineum is done to evaluate possible
abnormalities of pelvic floor muscle function.
• EMG activity is measured during both filling and emptying.
• EMG is performed via electrodes placed in (needle
electrodes) or near (surface electrodes) the muscle to be
measured.

53. • Most important information obtained from
sphincter EMG is whether there is
coordination or not between the external
sphincter and the bladder.
• EMG activity gradually increases during
filling cystometry (recruitment) and then
cease and remains so for the time of voiding.

54. • Failure of the sphincter to relax or stay
completely relaxed during micturition is
abnormal.
• In pt with neurologic disease, this is called
detrusor-sphincter dyssenergia.
• In the absence of neurologic disease, it is
called pelvic floor hyperactivity,or
dysfunctional voiding.

55. CYSTOMETROGRAPH

56. URODYNAMIC RISK FACTORS
• Following urodynamics findings are potentially dangerous
and usually require intervention to prevent upper and lower
urinary tract decompensation:
• 1. Impaired compliance
• 2. Detrusor external sphincter dyssynergia (DESD)
• 3. Detrusor internal sphincter dyssynergia (DISD)
• 4. High-pressure detrusor overactivity present throughout
filling
• 5. Elevated detrusor leak point pressure (>40 cm H2O)
• 6. Poor emptying with high storage pressures