Urodynamic studies (1)

UrodynamicUrodynamic
StudiesStudies
Dr G Praveen Chandra

Introduction
• Urodynamics is the general term for the study
of the storage and voiding
function/dysfunction of the lower urinary
tract.
• It is crucial that the UDS reproduce the
patient’s presenting symptoms.

UDS Armamentarium
• Noninvasive UDS:
• Uroflowmetry
• Post-void residuals
(PVR)
• Invasive UDS:
• Filling Cystometry
• Pressure-flow micturition studies
• Electrophysiological studies
• Urethral pressure studies
• Video-urodynamic studies

Uroflowmetry
• Non invasive study
• An 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

Uroflowmetry(cont.)
• Recorded variables during uroflowmetry study:
-flow pattern
-voided volume
-maximum flow rate(Q max)
-flow time
-average flow rate(Q mean)
-time to maximum flow
-voiding time
-hesitancy

Uroflowmetry(cont.)
• Optimal voids 200 to 400cc
• voids < 150cc are difficult to interpret.
• Pt should be well hydrated with full bladder, but
not overly distended bladder.
• study should be performed in privacy and pt
encouraged to void in his normal fashion.
• voided volume, pt’s position, method of bladder
filling, and type of fluid should be recorded.

Uroflowmetry(cont.)
• Max flow rate and shape of the curve are more
reliable indicators of BOO.
• Q max is the most reliable variable in detecting
abnormal voiding, and influenced by several
factors:
-age & sex: decreases with age in men.
-chance: multiple trials increases accuracy.
-volume of voided urine: 150 cc or more.

Uroflowmetry(cont.)
• Uroflow and BOO:
- In general the test alone is insufficient to diagnose
BOO.
- Qmax < 12cc/s…a good indicator for obstruction.

High Flow Obstruction
Concept
High flow infravesical obstruction in male
patients with severe prostatism is defined by
a maximum flow rate of more than 15 ml.
per second and a vesical pressure exceeding 100
cm. water at maximum flow rate

Residual urine volume
• It integrates the activity of the bladder and the
outlet during emptying.
• Can be measured directly by bladder
catheterization, or estimated by USG.
• What is considered a normal PVR is controversial.
- in adults a value less than 25ml is considered
normal , and PVR > 100 ml warrants careful
surveillance and/or treatment.

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

Indications(cont.)
• 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.

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

Patient preparation and
precautions
• Prior to UDS
• A working diagnosis should be entertained
• history and physical examination
• 3-day voiding diary
• certain drugs should be held
• UDS should be deferred in the presence of
• UTI
• recent instrumentation (cystoscopy)

• Routine prophylactic antibiotics not necessary.
• High risk pts. (cardiac valve, orthopedic prosthesis, GU
prosthesis, pacemakers) parenteral antibiotic
prophylaxis might be necessary.

Patient preparation and
precautions(cont.)
• Pts. who are catheter dependent ideally should have
the catheter removed and be placed on CIC before UDS
is performed.
• The test should be done in private area with as few
observers as possible.

• In neuropathic pts., one must be cautious of
autonomic dysreflexia .
• If the symptoms occur then the bladder should
be emptied immediately and antihypertensive
drug (nifedipine, hydralazine) might need to
be given.

Cystometry
• Measurement of intravesical bladder pressure during
bladder filling.
• Bladder access by transurethral catheter, or rarely by
percutaneous s/p tube.
• Bladder filling either by diuresis or filling through a
catheter.
• Filling medium either gas (CO2) or liquid (water, saline
or contrast material at body temp).

Cystometry(cont.)
• Liquid cystometry is more physiologic.
• Ideally, filling should be performed in standing position
• RATE of 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 filling rates.
• The reference point is the superior edge of the
symphysis pubis.
• All systems should be zeroed to atmospheric
pressure.
• No air bubbles

Cystometry(cont.)
• Single Vs multi-channel UDS:
-single: Pves only
-multi: Pves, Pdet, Pabd
• Provocative maneuvers:
- to unmask abnormalities of detrusor
function(UC)
- posture change(erect), coughing, jumping.

Phases ofPhases of
cystometrogramcystometrogram

Cystometry(cont.)
• Measurements via cystometry:
- Bladder capacity
- Sensation
- Compliance
- Detrusor stability

Cystometry(cont.)
• Measurements via cystometry
• BLADDER CAPACITY…volume at which a patient
with normal sensation feels that micturition can no
longer be delayed.
-normal=400-500ml. Can’t be determined in pts. with
impaired sensation.
• Sensation: first ,normal, strong desire to void.

• Bladder compliance: change in detrusor
pressure over a given change in volume.

Cystometry(cont.)
• Compliance:
- 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 cmH2o.
- Decreased compliance: <20 ml/cmH2o, poorly
distensible bladder.

Cystometry(cont.)
- Leak point pressures:
*Detrusor LPP is the lowest bladder pressure where urethral leak
of urine is first identified (risk with > 40cm H2O).

Valsalva LPP is the pressure that causes leakage of urine in the
absence of bladder contraction(using valsalva maneuver,
cough).
If there is no leakage at high pressures, then the urethra is
unlikely to be the cause of the pt.’s incontinence, and rather
the bladder is the more likely cause.
VLLP < 60 cm H2O: Significant ISD
VLLP= 60-90 cm H2O :equivocal
VLLP > 90 cm H2O : No ISD

• Detrusor overactivity
• Is a UDS observation characterized by involuntary
detrusor contractions during the filling phase which
may be spontaneous or provoked
• Neurogenic detrusor overactivity
• Detrusor overactivity accompanied by a neurologic
condition.
• This term replaces detrusor hyperreflexia

Cystometry(cont.)
•factors that may alter the CMG
include
• incompetent outlet,
• massive reflux,
• rapid fill,
• lack of pt cooperation &
• substances irritative to bladder.

Cystometry(cont.)
• Normal CMG:
- capacity 400-500ml
- Constant low pressure that does not reach
more than 6-10 cmH2o above baseline at the
end of filling.
- Provocative maneuvers should not provoke a
bladder contraction normally.

Pressure-Flow
Micturition Studies
• Simultaneous measurement of bladder pressure and
flow rate throughout the micturation cycle.
• The best method of quantitatively analyzing voiding
function.
• Access to bladder via transurethral or s/p.

• Catheter larger than 8 Fr may obstruct and
affect pressure flow recordings.ideally size
should be 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

PFS ( cont.)
• Terminology:
- the detrusor opening pressure:
Pdet recorded at the onset of the flow.
- the detrusor pressure at maximal flow:
the magnitude of micturition contraction at the time
when the flow rate is at its maximum.

PFS ( cont.)
• Detrusor opening pressure > 80cm may indicate outflow
obstruction.
• detrusor pressure at Qmax > 100cm implies outlet
obstruction even if flow rate is normal.
• No consensus regarding critical value for pressure and flow
that is diagnostic for obstruction.
• Pdet = Pves – Pabd
• Normal male generally voids with Pdet 40-60 cmH2O, and
woman with lower pressure.
• Pdet more accurately measures bladder wall contractions.

PFS ( cont.)
• Role of pressure-flow studies:
- to differentiate between pts. with a low Q max
sec. to obstruction, from those sec. to poor
contractility.
- Identify pts. with normal flow rates but high
pressure obstruction.

PFS ( cont.)
Indications for pressure-flow studies:
- LUTS in pt with hx of neurologic disease (CVA, Parkinson’s).
- LUTS with normal flow rates (Qmax > 15cc/min).
- younger men with LUTS.
- men in whom LUTS are suggestive of bladder instability
rather than flow disorder.
- men with little endoscopic evidence of prostate occlusion.

PFS ( cont.)
• Pressure-flow plots:
- Many models available.
1- Abrams-Griffiths number.
2- ICS provisional nomogram

PFS ( cont.)
• Abrams-Griffiths number: BOOI:
• Divides obstructed from equivocal from unobstructed
pattern.
• plot of PdetQmax vs. Qmax
• AG number = PdetQmax – 2 x Qmax
• Can grade the degree of obstruction before and after
treatment.
• BOOI > 40 = obstructed;
• BOOI 20−40 = equivocal; and
• BOOI < 20 = unobstructed

Bladder Contractility Index: BCI
• Schaefer described the formula for BCI:
• BCI= Pdet @ Qmax + 5 (Qmax) .
• strong contractility is a BCI of >150,
• normal contractility ----BCI of 100–150
• weak contractility ----- BCI of < 100.

Bladder Contractility
Index: BCI

Electrophysiologic
testing
• Sphincter EMG studies the bioelectric potentials
generated in distal striated sphincter mechanism.
• Two different levels:
1-Kinesiologic studies:
• examine sphincter activity during bladder filling
and voiding.
2-Neurophysiologic tests:
• examine the integrity of innervation of the
muscle.
• Require considerable expertise.

Electrophysiologic
testing(cont.)
• Overall,the most important information
obtained from sphincter EMG is whether there
is coordination or not between the external
sphincter and the bladder.

Electrophysiologic
testing(cont.)
• Kinesiologic Studies:
- Signal may be recorded by surface electrodes or by hooked
wire electrodes introduced into the periurethral muscle.
- Before filling, pt asked to demonstrate volitional control of
sphincter (intact pyramidal tracts).
- Bulbocavernosus reflex is tested (intact sacral arc).
- EMG activity gradually increase during filling cystometry
(recruitment) and then cease and remains so for the time
of voiding.
- Once bladder is empty, sphincter EMG activity resumes.

Kinesiologic
Studies(cont.)
• Failure of the sphincter to relax or stay completely
relaxed during micturation 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.
• Kinesiologic studies do not diagnose neuropathy
but may characterize effects of it.

Kinesiologic
Studies(cont.)
• Important role in identification of abnormal
sphincter activity in pts with neurogenic
bladder dysfunction and in those with voiding
dysfunction of behavioral origin.
• This study has little role to play in routine UDS
evaluation of incontinent or obstructed pts in
whom neuropathy is not suggested by other
clinical findings.

Normal urodynamics tracing
• The bladder slowly fills with no change in
detrusor pressure thus exhibiting normal
compliance.
• There are no uninhibited detrusor contractions
noted prior to the full void attempt (after
permission to urinate was given by the
examiner) and thus no DO noted.

• The EMG shows recruitment leading up to the
contraction thus maintaining continence and
creating an adequate void pressure
• But it notably quiets at the peak detrusor
pressure allowing an unobstructed
coordinated void to completion.

Elevated compliance with an
acontractile bladder
• Bladder volume rises to approximately 820 mL
with minimal change in Pves.
• Patient is asked to void at a volume of 820 mL
with no appreciable detrusor function or
change in sphincteric EMG.
• This pattern of voiding function was taken
from a patient with a sacral level lesion.

Detrusor overactivity
• Normal compliance with normal to high
volume of 700 mL.
• Frequent uninitiated detrusor contractions
throughout the filling period.
• This pattern is often encountered in
Parkinson’s and MS patients.

Low-volume bladder with
loss of compliance
• Throughout the filling phase there is consistent rise of
Pves and Pdet, despite low volumes of 200 mL, which
continue above 50 cmH2O without an appreciable
void attempt.
• No notable detrusor overactivity or DSD identified.
• This pattern is often encountered in spina bifida
patients.

Urethral pressure
profilometry
• Static urethral pressure profile. (at rest)
• Stress urethral pressure profile. ( during
straining)
• Micturational urethral pressure profile. (during
voiding)
• Valsalva LPP.

Urethral pressure
profilometry
• UPP is recording of intraluminal pressure along
length of urethra
• Study performed during slow retraction of a
catheter with side holes (0.5mm/s)

• bladder pressure should be measured
simultaneously to exclude effects of an
associated detrusor contraction
• Static UPP: cannot diagnose stress urinary
incontinence, sphincter dyssynergia, or BOO. It
is not a functional test

Urethral pressure
profilometry
• Stress UPP:
- Monitor urethral pressure and bladder pressure
simultaneously
- performed as the profile catheter is withdrawn
along the urethra during periods of
intermittent stress (cough)
- technically difficult to perform, and movement
artifact of catheter is common

Urethral pressure
profilometry
• Micturational UPP:
- To evaluate the bladder outlet.
- same as the standard UPP, only the pt voids while the catheter is being
withdrawn.
- during voiding, bladder and urethral pressures are identical.
- if obstruction exists in urethra, the intraurethral pressure distal to
obstruction is less than that within bladder or proximal to obstruction, thus
when a significant pressure drop is encountered on withdrawal, this
corresponds to the site of obstruction.
- however, distortion artifacts are considerable and location of catheter is
inexact.

Video-Urodynamics
• UDS with simultaneous fluoroscopic image of the 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 incontinence
• neurogenic bladder dysfunction
• identification of associated pathology

Urodynamic studies (1)

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Urodynamic studies (1)