Bladder Physiology, Neurogenic Bladder, and Incontinence Types

Bladder Physiology and Neurogenic Bladder

  • Bladder Function

    • Urine storage (collection) phase: 90% of the bladder's time.

    • Emptying (voiding) phase: 10% of the bladder's time.

Bladder Composition

The bladder comprises 4 layers:

  • Mucosa (contains elastic tissue)

  • Submucosa

  • Muscle

  • Serosa

The bladder's primary functions are storing and emptying urine; it does not secrete hormones or IL.

Phases of Bladder Function

Filling Phase (Urine Storage)

  • Characterized by increasing urine volume at low intravesical pressure with closed sphincters.

Voiding Phase

  • Involves coordinated contraction of bladder muscle with concomitant decrease of resistance at the level of smooth and striated sphincters (synergy).

  • This phase is under parasympathetic control while storage is under sympathetic control.
    *Elastic collagen is present.

Elastic Tissue in the Bladder

  • The bladder has elastic tissue which allows it to compensate for increases in urine volume without a significant increase in pressure, up to a certain limit.

  • If the limit is exceeded, it can lead to voiding or rupture.

  • Conditions like recurrent infections, UTIs, chemotherapy, or radiotherapy can cause the elastic tissue to become fibrotic, reducing capacity and causing incontinence (low compliance).

Sphincters

  • Internal Sphincter:

    • Involuntary control.

    • Supplied by the autonomic nervous system (sympathetic and parasympathetic).

    • Smooth muscle of the bladder neck and proximal urethra.

  • External Sphincter:

    • Voluntary control.

    • Supplied by the somatic nervous system.

    • Extrinsic or extramural striated sphincter; bulky skeletal muscle that surrounds the urethra at the level of the membranous urethra and middle segment in females.

  • Storage requires relaxation of the bladder and contraction of both sphincters; defects in either can cause incontinence.

Bladder Anatomy

  • Bladder: wrinkled.

  • Trigone: smooth, between the two ureteric orifices and bladder neck.

    • Internal sphincter at the level of the bladder neck and proximal urethra.

    • External sphincter at the level of the pelvic floor (membranous urethra and middle segment in females), distal to the internal urethral sphincter.

Innervation

  • Parasympathetic (S2-S4):

    • Supplies bladder and smooth sphincter.

    • Excites bladder and relaxes internal sphincter, promoting voiding.

  • Sympathetic (T10-L2):

    • Supplies smooth muscle of bladder base, internal sphincter, and proximal urethra.

    • Inhibits bladder and excites internal sphincter, promoting storage.

  • Somatic (S2-S4):

    • Travels to striated sphincter via the pudendal nerve.

    • Under voluntary control, causing either contraction or relaxation.

Neurotransmitters and Receptors

  • Acetylcholine acts on muscarinic receptors (M1-M5, mainly M2 and M3) in the bladder, leading to contraction in the parasympathetic pathway.

Summary of Innervation

  • Para (S2-S4): Detrusor muscle + internal sphincter

  • Sympa (L1-L3): Detrusor muscle + internal sphincter

  • Somatic (S2-S4): External sphincter

Incontinence

  • Definition: Inability to hold urine.

  • High prevalence in females (90% will experience at some point) and older males or post-operative males.

Types of Incontinence

1. Urge Incontinence

  • Inability to hold urine associated with or preceded by urgency.

  • More common in females, especially post-menopausal.

  • Patients feel the need to go to the bathroom but cannot make it in time, leading to leakage.

  • Can be due to detrusor overactivity (DOA) or low compliance.

  • Treatment: Anti-cholinergics.

  • Problem in filling phase.

  • Nocturnal enuresis: Involuntary urination at night.

2. Stress Incontinence

  • Inability to hold urine due to increased intra-abdominal pressure.

  • Can be due to sphincter deficiency (in males) or pelvic muscle weakness (in females).

  • Common causes include coughing, laughing, or sneezing.

  • Prolapse is the main cause ( recurrent delivery -leakage ).

3. Overflow Incontinence

  • Mainly in males with bladder outflow obstruction (e.g., prostate issues).

  • Bladder overfills, leading to leakage due to chronic obstruction and loss of sensation.

  • Common in diabetic patients due to neuropathy.

  • The bladder pressure exceeds sphincter pressure.

4. Continuous Incontinence

  • Continuous leaking of urine without aggravating factors.

  • Causes:

    • Fistula (VVF: Vesicovaginal fistula) - abnormal connection between two organs (e.g., bladder and vagina).

    • Ectopic ureter (in males) - ureter opens below the external sphincter.

  • Any urine will flow directly, it's extra urethral incontinence

5. Mixed Incontinence

  • More than one type of incontinence in the same patient (e.g., stress + urge).
    Incontinence (at filling phase)-definition: inability to hold urine

Detrusor Overactivity (DOA)

  • Abnormal detrusor contraction during the filling phase.
    We do rule out the infection with urine analysis and culture, Because it gives false reading and complications.
    Before Analysis urine, we need to use catheters

Urodynamic Studies

  • Used to assess bladder function.

  • Involve the use of catheters to measure pressures.

Pressures Affecting the Bladder

  • Intravesical pressure: Measured directly.

  • Rectal pressure (Abdominal pressure): Measured directly.

  • Detrusor pressure: Calculated indirectly.

Formula

DetrusorPressure=IntravesicalPressure−AbdominalPressureDetrusor Pressure = Intravesical Pressure - Abdominal Pressure

Abdominal pressure = rectal pressure = intra-abdominal pressure

Cystometry

  • Filling phase has 4 curves.

  1. Abdominal pressure

  2. Intravesical pressure

  3. Detrusor pressure

  4. Volume instilled

*Voiding phases has 5 curves:

  1. Abdominal pressure

  2. Intravesical pressure

  3. Detrusor pressure

  4. Urine volume

  5. Urine flow rate (bell curve)

Normal Values

*Filling rate: Capacity/10Capacity/10 ml per minute

  • Adult Urodynamic Capacity: 450-500 ml.
    *Filling rate calculated based on (equation: age + 2) * 30
    Urine flow rate:
    *In male: 15−2015-20 ml/second
    *In female: 20−2520-25 ml/second, short urethra weak of

Interpretation

  • Detrusor pressure during filling should be zero; if not, it indicates contraction and potential incontinence.

  • Filling faster than physiological rate: false positive.

  • Filling slower than physiological rate: false negative.

Detrusor Overactivity (DOA) Explained

  • Used to observe the urodynamic of involuntary detrusor contractions during the filling phase.

  • Symptoms: Urgency, nocturia, frequency, and urge incontinence.

  • Fluid must be at room temperature.

Reading Results

*Curves:

  1. Abdominal pressure (red) from catheter in vagina or abdomen (rectal).

  2. Intravesical pressure (blue) from catheter in bladder lumen.

  3. Detrusor pressure (pink): pp inside bladder muscle (used to see the defect).

  4. Volume filled up (green).

  • If contraction occurs (peak), it indicates involuntary leaking of urine (incontinence) = detrusor overactivity.

Retention

  • Two differential diagnoses: Obstruction or not.

  • If voiding flow is zero, consider obstruction.

Voiding phase
Q max: maximum flow rate: rate is low
*Obstruction-> Q max low but detrusor pressure is veryy high to overcome obstruction
*Weak contractions during voiding/ neuronal problem -> Q max is low

Retention DDX

  • Sphincters dyssynergia Neurogenic bladder.

*DM ( Neuropathy) Another ddx :
Stroke pts affecting urination centers in brain
Disc prolapse.
Contractil or hypocontractil, Bladder obstruction, Neurogenic
To have voiding :

  • contraction of detrusor muscle & open pathway.

Management of Hypocontractile Bladder

  • Acetylcholinesterase inhibitors (e.g., neostigmine & physostigmine) to increase acetylcholine levels.
    *cholinergic or Botox:
    Muscarinic receptors mainly M2 M3 in the bladder:
    Agonist-> contraction
    *Anti cholinergic : overactive DOA:
    Augmentation cystoplasty
    Need long term Foley's catheter
    Intermittent self catheterization is an option to the one way catheter

Augmentation Cystoplasty

  • Take part of the bowel and attach it to the bladder to increase capacity.

Compliance

*Formula: Change in volume / change in pressure

  • Supposed to be constant.

  • If it increases, it indicates low compliance.

Low Compliance

*Females with recurrent UTI.
*CA pts taking chemotherapy or radiotherapy.

  • Bladder surgeries (fibrosis).

Stress Incontinence Diagnosis

*To diagnose, ask the patient to cough to see if urine leaks with normal detrusor pressure.
*If there is a contraction during filling, the cause is DOA, if normal, check the intra-abdominal pressure
*Treat the prolapse or increase sphincter tightness with a bulking agent.
Pelvic floor muscle

Overflow Incontinence

*The bladder volume and pressure are higher than sphincter pressure = leaks urine due to chronic obstruction + loss of sensation.
*Mainly in male.
*Treatment is by relief of obstruction.
Diabetic or Spinal cord injury