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Urodynamic Studies, an overview :

Urodynamic Studies, an overview Prof. Dr. Ziad Al-Naieb MD., PhD., FRCS


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:

UDS Armamentarium cystometry uroflowmetry Urethral pressure studies Pressure-flow micturation studies Video-urodynamic studies Electrophysiologic studies


Indications Incontenance: -recurrent incontenance in whome surgery is planned. -mixed urge and stress symptoms. -associated voiding problems -pt with neurologic disorders -pt with mismatch between signs and symptoms.


Indications(cont.) 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 incontenance,recurrent infection,reflux,or upper tract changes.

Clinical roles:

Clinical roles Characterization of detrusor function evaluation of bladder outlet evaluation of voiding function diagnosis and characterization of neuropathy.

Patient preparation and precautions:

Patient preparation and precautions Prior to UDS A working Dx should be entertained hx and physical 3-day voiding diary certain drugs should be held UDS should be deferred in the presence of UTI recent instrumentation (cystoscopy) Routine prophylactic abx not necessary. High risk pts (cardiac valve,orthopedic prosthesis,GU prosthesis,pacemakers) parental antibiotic prophylaxis might be necessary.

Patient preparation and precautions(cont.):

Patient preparation and precautions(cont.) Pt who are catheter dependent idealy should have the catheter removed and be placed on CIC for a period before UDS performed. The test should be done in private area,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. filling medium either gas (CO 2 ) or liquid (water, saline, or contrast material at body temp). liquid cystometry is more physiologic. ideally, filling should be performed in standing position.


Cystometry(cont.) 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. 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) - fast fill cystometry, posture change(erect), coughing, jumping.

Phases of cystometrogram:

Phases of cystometrogram


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. - maximal bladder capacity,functional bladder capacity,anesthetic bladder capacity. sensation , first ,normal,strong desire to void,urgency,pain. 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. Decrease compliance = > 20 ml/cmH2o, poorly distensible bladder. Increase compliance.


Cystometry(cont.) - Leak point pressures: *Detrusor LPP , the lowest bladder pressure where urethral leak of urine is first identified (risk with > 40cm H 2 O). * Valsalva LPP ,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( < 150cmH2O) then the urethera is unlikely to be the cause of the pt’s incontinence,and rather the bladder is the more likely cause. VLLP > 60 cm H 2 O: significant ISD VLLP 60-90 cm H 2 O :equivocal VLLP < 90 cm H 2 O : urethral hypermobility


Cystometry(cont.) Involuntary contractions: detrusor stability, reflects the integrity of central nervous system control over bladder function. Unstable bladder, contract either spontaneously or with provocative maneuvers during filling cystometry, while pt is trying to inhibit micturation.it is any involuntary pressure rise that is associated with urgency. Detrusor hyperreflexia: in pt with neurologic disease. Detrusor instability: in absence of neurologic disease.


Cystometry(cont.) Involuntary contractions: hyperactive bladder is one that demonstrates instability, hyperreflexia, or low compliance. motor urge incontinence , pts with urgency and urge incontinence in whom unstable detrusor contractions can be demonstrated on UDS sensory urgency , pts in whom the same symptoms are present but have a stable bladder on UDS. *ambulatory monitoring has confirmed the presence of unstable bladder contractions in up to 69% of normal volunteers.


Cystometry(cont.) factors that may alter the CMG include an incompetent outlet, massive reflux, rapid fill, lack of pt cooperation, and 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.

Cystometry(cont.) Pharmacologic tests::

Cystometry(cont.) Pharmacologic tests: Bethanechol supersensitivity test: an attempt to distinguish between a neurogenic and a myogenic origin in pt with an acontractile bladder. Denervated bladder develops hypersensitivity to the normal excitatory neurotransmitters. end-fill pressure obtained after infusion of liquid at 1ml/s to a volume of 100cc( to determine average end-fill pressure) after this, 0.035mg/kg of bethanechol chloride is injected s/c. denervated bladder shows an increase in pressure of >15cm H2O above baseline.

Pharmacologic tests(cont.):

Pharmacologic tests(cont.) positive test suggest an interruption in the afferent or efferent peripheral or distal spinal innervations of the bladder. However, the test shown to be unreliable (76% sensitive,50% specific) for neurogenic bladder.

Pharmacologic tests(cont.):

Pharmacologic tests(cont.) Ice water test: - Differentiate upper from lower motor neuron lesions. - Based on the principle that mucosal temperature receptors can elicit a spinal reflex contraction of the detrusor, normally inhibited by supraspinal centers, which is interrupted in UMNL. - rapid injection of the bladder with ice water. - fluid is left for 1 min. - if sustained bladder contraction and fluid is expelled during this period, or increase intravesical pressure, test is +ve. - +ve test in 91-97% of suprasacral lesions; it is almost never +ve in LMN lesions.


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 3 methods used gravimetric rotating disk electronic dipstick


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 curve may produce 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. -McLoughlin (1990) demonstrated that Qmax < 12cc/s was a good indicator for obstruction. -concept of high flow obstruction: Qmax < 15ml/sec,detrusor pressure < 100cmH2O in symptomatic patient.

Residual urine volume:

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 uss What is considered a normal PVR is controversial. in adults a value less than 25ml is considered normal , and PVR < 100 warrant carefull surveillance and/or treatment. A PVR < 100 ml in elderly may under certain circumstances be considered acceptable.

Urethral pressure profilometry:

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:

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:

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:

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.

Pressure-Flow Micturition Studies:

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.):

PFS ( cont.) Terminology: - the detrusor opening pressure : Pdet recorded at the onset of measured flow. - the detrusor pressure at maximal flow : the magnitude of micturation contraction at the time when the flow rate is at its maximum. pressure < 100 cmH2O indicate outlet obstruction even if the flow rate is normal.

PFS ( cont.):

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.):

PFS ( cont.)

PFS ( cont.):

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

PFS ( cont.):

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 whom LUTS sx of bladder instability rather than flow disorder. - men with little endoscopic evidence of prostate occlusion.

PFS ( cont.):

PFS ( cont.) Pressure-flow plots: for PFS equivocal results. Many models available. 1- Abrams-Griffiths nomogram. 2- Schafer method. 3- ICS provisional nomogram

PFS ( cont.):

PFS ( cont.) Abrams-Griffiths nomogram Divides obstructed from equivocal from unobstructed pattern. plot of P det Q max vs. Q max pts in the equivocal group, if minimum voiding pressure is > 40 cm H 2 O, then obstruction is present grading of obstruction AG number = (P det Q max) – 2(Q max) Can grade the degree of obstruction before and after treatment.

Schafer method:

Schafer method

ICS provisional nomogram:

ICS provisional nomogram


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



Electrophysiologic testing:

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.):

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.):

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.):

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.):

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 have little role to play in routine UDS evaluation of incontinent or obstructed pts in whom neuropathy is not suggested by other clinical findings.

Neurophysiologic Recordings:

Neurophysiologic Recordings To diagnose and characterize the presence of neuropathy or myopathy. special needle inserted directly into the muscle to be tested. motor unit action potentials (MUAP) in health and disease differ. Normal distal urethral sphincter muscle has a biphasic or triphasic wave form,but denervated muscle has polyphasic potentials. MUAP studies find their role in evaluation of pt with bladder dysfunction of unknown cause in whom neuropathy is suspected.

Nerve Conduction Studies:

Nerve Conduction Studies Stimulation of a peripheral nerve and monitoring of time taken for a response to occur in its innervated muscle. Latency: is the time from stimulation till response. A test of the integrity of reflex arc. Pt with suprasacral lesions may have normal or low latencies(26-30 msec.) Example: bulbocavernous reflex latency.



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