Physiology of Micturition and Voiding Disorders

Physiology of Micturition

• The smooth muscle of the bladder wall (detrusor muscle) is composed of an interlacing network of fibers running in various directions.
• The male urethra consists of prostatic, membranous, and spongy parts, with a total length of about eight inches.
• The proximal urethral sphincter can maintain passive continence, but opens widely in association with a detrusor contraction.
• During normal filling, there is a gradual increase in urethral resistance, which helps to prevent urine loss as the bladder fills.
• The detrusor should remain inactive with no involuntary contractions during filling.
• When the bladder has filled to a specific volume, tension receptors in the bladder sense fullness, and a voluntary micturition reflex is initiated.

Neural Supply for the Lower Urinary Tract

• The autonomic nervous system innervates the smooth muscle detrusor and proximal sphincters.
• The somatic nervous system innervates the striated external sphincter and pelvic floor muscles.
• The sympathetic nervous system is responsible for filling, while the parasympathetic nervous system is responsible for emptying.

Reversible Causes of Urinary Incontinence

• Delirium
• Infection
• Atrophic vaginitis
• Pharmacological
• Psychological
• Endocrine
• Restricted mobility
• Stool impaction

Types of Urinary Incontinence

• Urge Incontinence: involuntary loss of urine associated with a strong desire to void (urgency), often associated with detrusor instability.
• Stress Incontinence: involuntary loss of urine during coughing, sneezing, laughing, or physical activity that increases intra-abdominal pressure.
• Mixed Incontinence: a combination of symptoms of urge and stress incontinence.
• Overflow Incontinence: involuntary loss of urine associated with overdistension of the bladder.

Management of Urinary Incontinence

• Kegel exercises
• Behavioral therapy
• Functional Magnetic Stimulation (FMS)
• Electrical Stimulation
• Biofeedback
• Acupuncture

Electrical Stimulation

• Surface stimulation: TENS, functional electrical stimulation, pudendal nerve stimulation, lower limb stimulation, functional magnetic stimulation, interferential stimulation, posterior tibial nerve stimulation.
• Neuro-modulation: intravesical electrical stimulation, direct bladder stimulation, implanted sacral root stimulation.

Enuresis (Bed-wetting)

• Defined as repeated voiding of urine into clothes or bed at least twice a week for at least 3 consecutive months in a child who is at least 5 years old.
• Two physical functions prevent bedwetting: anti-diuretic hormone (ADH) production and the ability to wake up when the bladder is full.
• Classification of enuresis: daytime symptoms, nocturnal symptoms, mono-symptomatic, poly-symptomatic, primary, secondary.

Causes of Bed-wetting

• Neurological-developmental delay
• Genetics
• Bladder problems
• Insufficient anti-diuretic hormone (ADH) production
• Psychological
• Infection/disease
• Sleep disorders
• Improper toilet training

PT Treatment of Enuresis

• Reassure the child and parents that the condition is self-limited and avoid punitive measures.
• Proper toilet training
• Behavioral treatment
• Alarm treatment
• Acupuncture
• Motivation and psychological support
• Fluid intake restriction after 6 or 7 pm
• Voiding at bedtime
• Avoiding extraneous caffeine and diuretic fluids after 4 pm
• Star chart for dry nights
• Waking children a few hours after they go to sleep to have them void often allows them to awaken dry.