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Urodynamic Lingo

The Many Cs of Urodynamics

• Capacity: volume
• Compliance: DLPP
• Contractility: DO, DUA
• Coordination: DESD
• Continence: VLPP
• Conscious sensation: increased/decreased
• Complete emptying: DUA, BOO
• Clinical obstruction: BOO

Broad classifications for voiding dysfunction

• Storage dysfunction vs emptying dysfunction
• Bladder dysfunction vs bladder outlet dysfunction

UDS tools

• Cystometry: pressure/volume relationship of the bladder during filling, measures sensation, compliance, capacity, and presence of detrusor activity
• Electromyography (EMG): measurement of sphincter (and pelvic) muscle depolarization
• Pressure-flow studies: bladder pressure and urine flow rate during emptying
• Uroflowmetry: measurement of urine flow rate
• Video UDS: fluoroscopy during UDS

UDS Measurements

• Compliance: change in volume over change in pressure, < 6cm water increase considered normal
• Cough leak point pressure (CLPP): urinary leakage with cough, considered superior to VLPP
• Detrusor leak point pressure (DLPP): detrusor pressure at which urine leakage occurs in the absence of detrusor contraction or increased abdominal pressure, 40cm water usually used as cutoff for concern for renal injury
• Maximum urethral closure pressure (MUCP): max difference between urethral and intravesical pressures
• Post Void Residual: amount of urine left in bladder after urination, no universal definition, elevated PVR caused by DUA and/or BOO
• Urethral pressure profile: fluid pressure needed to open a closed urethra
• Valsalva leak point pressure (VLPP): intravesical pressure at which urine leakage occurs in the absence of a detrusor contraction
• Volumes: first sensation, sensation of fullness, desire to void, capacity

Abnormal UDS Findings

• Autonomic dysreflexia: exaggerated sympathetic response to afferent visceral/painful stimulation, causes flushing, sweating, headache, HTN, and reflex bradycardia
• Detrusor External Sphincter Dyssynergia (DESD): involuntary external sphincter contraction during detrusor contraction
• Filling (irritative) LUTS: frequency, urgency, nocturia, incontinence
• Increased filling sensation: increased sensation at low volumes in absence of involuntary contractions, leads to decreased “functional” but not anatomic bladder capacity
• Intrinsic sphincter deficiency (ISD): leak point pressure less than 60cm water or MUCP less than 20cm water
• Neurogenic bladder (NGB): abnormal bladder function due to neurologic disease
• Occult SUI: SUI only after reduction of co-existent prolapse
• Overactive bladder (OAB): urgency +/- frequency, nocturia, incontinence
• Pelvic organ prolapse (POP): descent of anterior/posterior vaginal wall, uterus, vaginal apex
• Reduced filling sensation: decreased sensation throughout bladder filling
• Stress urinary incontinence (UDS): involuntary leakage during filling associated with increased intraabdominal pressure in the absence of detrusor contraction (AKA low VLPP)
• Stress urinary incontinence (symptom): complaint of involuntary urine leakage w/ effort, physical exertion, sneeze, cough
• Stress urinary incontinence (sign): observation of involuntary urine leakage w/ effort, physical exertion, sneeze, cough
• Urgency: sudden urge to void, difficult to defer
• Urinary incontinence: sudden urge to void with associated incontinence
• Voiding (obstructive) LUTS: slow stream, hesitancy, intermittency, incomplete emptying, postvoid dribbling

Interpreting UDS

Filling phase

• Detrusor pressure should remain near zero until voiding is initiated
• Pdet can differentiate between Valsalva and true detrusor contraction
• Impaired compliance: > 40, needs treatment to prevent upper tract injury, may be artificially decreased if reflux or diverticulum present
• Abdominal leak point pressure (ALPP): ability of sphincter to resist changes in abdominal pressure, can only be seen with SUI, < 60 indicates ISD, > 90 indicates minimal/no ISD
• CLPP and VLPP are both ways to measure ALPP, but VLPP tends to be lower
• Detrusor leak point pressure (DLPP): lowest detrusor pressure where leakage occurs in absence of detrusor contraction or increased abdominal pressure, higher value implies pressure transferred to upper tracts instead of inducing leakage
• Stress induced detrusor overactivity (SIDO): triggered by rise in abdominal pressure

Detrusor overactivity

• Urodynamic finding, may (not) be unrelated to OAB symptoms
• Seen in 14-18% normal patients, 50% who report urge incontinence may not demonstrate DO on UDS
• Terminal: occurs at cystometric capacity resulting in incontinence and possible bladder emptying
• Only 60-70% men and 40-50% with dry OAB demonstrate DO, whereas 90+% men with wet OAB will demonstrate DO
• Coexistent BOO may affect efficacy of OAB treatments (cause urinary retention), but OAB symptoms may improve if BOO is treated
• Terminal DO at diminished capacity is most likely predictor that OAB symptoms will persist after treating BOO

Emptying phase

• Normal voiding: relaxation of striated sphincter, detrusor contraction, opening of bladder neck and urethra, onset of urination
• Minimum volume 150mL recommended to assess uroflow curve
• Detrusor underactivity (DUA): low pressure and low flow, reduced contraction strength leading to prolonged emptying time
• Detrusor acontractility: no detrusor contraction on UDS
• Bladder outlet obstruction: high pressure and low flow
• Abrams Griffiths nomogram: BOOI = PdetQmax - 2 * Qmax
• Bladder contractility index (BCI, Schafer's lines): PdetQmax + 5 * Qmax

VideoUDS

• Indications: localize level of obstruction, detect incontinence, evaluate for reflux
• Assess bladder contour, trabeculations, diverticula, stones, reflux, bladder neck, urethra
• Only way to diagnose primary bladder neck obstruction

Tips for Diagnosing certain diseasess

Female SUI and Prolapse

• UDS is not required if a patient has uncomplicated SUI
• Consider UDS if: prior SUI surgery, prior prolapse surgery, significant LUTS, significant OAB symptoms, elevated PVR, unconfirmed SUI, neurogenic LUTS
• If no SUI demonstrated on UDS, remove catheter and repeat test (may be obstructing) - up to 50% women (and 35% men) with SUI symptoms but no SUI on UDS show SUI once catheter removed
• If prolapse present, reduce (pessary, vaginal pack) and repeat stress testing (occult SUI)
• Mixed incontinence without DO on UDS shows greater improvement after SUI surgery compared with OAB treatment

OAB, UUI, and Mixed Incontinence

• Consider UDS prior to surgical or irreversible treatments for OAB
• Consider if new or persistent urge symptoms after bladder outlet procedure
• Increased filling sensation decreases patient's functional bladder capacity
• Presence of BOO and SUI may complicate treatment decisions
• Absence of detrusor overactivity does not mean it is not clinically present
• OAB symptoms more likely to resolve after TURP if patient has terminal DO (as opposed to phasic DO)

Neurogenic Bladder

• Measure post-void residual and assess for underlying cause
• Assess for elevated DLPP (> 40) to determine whether upper tracts are at risk for injury
• Consider vUDS when concerned about anatomic obstructions
• Consider EMG if concerned about detrusor/sphincter dyssynergia
• The higher the spinal lesion, the more likely DESD is to occur

Lower Urinary Tract Symptoms

• Helps differentiate outlet obstruction, detrusor underactivity, detrusor overactivity, and sensory urgency
• Check post-void residual, use UDS to differentiate obstructed versus non-obstructed patients
• Consider UDS if considering surgical or irreversible treatments
• Significantly impaired compliance is the only UDS indication for treating BOO

Expected findings based on level of neurologic injury

Level of injury	Overall picture	Bladder	Sphincter	Synergy?	Lower limbs	Bulbocavernosus Reflex
Suprapontine	Detrusor overactivity	Spastic	Normal	Yes	Normal	Present
Suprasacral cord	Detrusor/sphincter dyssynergia		Spastic	No	Spastic
Sacral cord or below	Acontractile detrusor	Flaccid	Flaccid		Flaccid	Absent

References

• AUA Core Curriculum
• Brucker, B. and V. Nitti. "Urodynamic and Video-Urodynamic Evaluation of the Lower Urinary Tract." Campbell-Walsh Urology 12 (2020).
• Reynolds, W. and J. Cohn. "Overactive Bladder." Campbell-Walsh Urology 12 (2020).
• Wieder JA: Pocket Guide to Urology. Sixth Edition. J.Wieder Medical: Oakland, CA, 2021.
• Winters, J. Christian, et al. "Urodynamic studies in adults: AUA/SUFU guideline." The Journal of urology 188.6 (2012): 2464-2472.