chapter 35: disorders of bladder and lower urinary tract

urinary bladder

• hollow, muscular, distensible organ located in pelvic cavity, behind pubic symphysis

bladder wall consists of 3 main layers:

• mucosa and submucosa: inner lining made of transitional epithelium (urothelium)

• muscular layer: smooth muscle called detrusor

• serosa: outer covering

trigone is a triangular area on:

• internal floor of bladder, formed by:

  • two ureteric openings

  • one internal urethral opening

two main sphincters of urinary bladder:

• internal urethral sphincter: located at bladder neck, surrounding beginning of urethra

  • made of smooth muscle, continuous w/ detrusor muscle — involuntary

  • controlled by sympathetic nervous system

• external urethral sphincter: located around the urethra in deep perineal region

  • made of skeletal muscle - under voluntary control

  • innervated by pudendal nerve (S2-S4)

micturition

• process of urination is micturition

• stretch receptors in bladder walls send signal to spinal cord

• smooth muscle in bladder wall contracts

• internal sphincter (smooth muscle) pulled open

• external sphincter (skeletal muscle) btwn bladder and urethra relaxes

in micturition, centers in brainstem and cerebral cortex override:

• basic reflexes under parasympathetic ctrl

• pudendal nerve sends impulses to external urethral sphincter

• sphincter contracts voluntarily - prevents urine from escaping

bladder obstruction

• bladder and urethral blockages can result from sev factors:

  • facal impaction or severe constipation: hard stool accumulates in rectum and may press against bladder or urethra

  • bladder tumor or metastases: tumors in bladder or cancer that has spread from other organs may block normal flow of urine

  • congenital obstruction of external urethral meatus

  • BPH: enlargement of prostate gland compresses urethra, making urination difficult - common in older men

early stages of bladder obstruction

• urinary obstruction results in compensatory changes, for early:

• bladder hypertrophy: becomes less flexible, making it difficult to expand and fill w/ urine

• hypersensitivity to stretch - ??

• decreased ability to suppress urination

later stages of bladder obstruction

• bladder wall continues to thicken

• detrusor contraction becomes too short: incomplete emptying and retention → frequency → urgency

long term obstruction leads to structural changes in bladder:

• trabeculea: detrusor muscle becomes hypertrophied, forming

• cellulae: small pockets dev btwn thickened muscle bundles

• diverticula: non-muscular pouches dev outward through weak areas btwn muscle bundles

incontinence

inability to voluntarily control urination, resulting in involuntary leakage of urine

enuresis

• involuntary urination by child age older than 4 years

• often related to developmental delay, sleep pattern, psychosocial aspect

retention

• inability to empty bladder completely, causing urine to remain in bladder

• spinal cord injury at sacral lvl can block micturition reflex

• may follow anesthesia (general or spinal)

neurogenic bladder

• bladder dysfunction caused by dmg or disruption of CNS, ANS, or peripheral nerves responsible for controlling bladder function, resulting in loss of norm bladder ctrl

• neurogenic bladder commonly presents in 2 forms:

  • spastic - failure to store urine

  • flaccid - inability to empty urine

dyssnergia

• common, w/ both detrusor and external urethral sphincter contracting at same time

• normalyl detrusor muscle contracts while external urethral sphincter relaxes

spastic bladder

• results from dmg to spinal cord above T12 lvl or dmg to brain - stroke, tumors, MS

• higher brain centers cannot ctrl reflex

• bladder cannot relax to fill urine

• contracts involuntarily, causing involuntarily, causing frequent, interrupted, or incomplete urination

flaccid bladder

• results from dmg to spinal cord below T12 or dmg to peripheral nerves controlling bladder - peripheral neuropathies

  • micturition reflex is inhibited

  • bladder cannot contract to empty - retention and overlow incontinence

treatment goals for neurogenic bladder

• prevent bladder overdistention: follow an individualized urination (or catheterization) schedule

• prevent UTIs: ensure bladder empties properly to reduce urine retention and bacterial growth

• prevent potentially life-threatening renal dmg: prevent urine from backing up into kidneys, which can cause hydroneprhosis

• reduce undesirable social and psychological effects of disorder: reduce anxiety and social isolation associated w/ loss of bladder ctrl

3 common types of urinary incontinence:

• overactive bladder/urge incontinence

• stress incontinence

• overflow incontinence

overactive bladder/urge incontinence

• involuntary contraction of bladder during filling

• person feels sudden, strong urge to urinate followed by involuntary urine leakage

stress incontinence (common in women)

• increased intra-abdominal pressure (coughing, sneezing, lifting) forces urine through sphincter

• result of pelvic floor muscle dysfunction - weakening due to pregnancies, childbirth

overflow incontinence

• retention of urine may be accompanied by overflow incontinence

• intravesical pressure exceeds urethral pressure - involuntary loss of urine

types of urinary incontinence picture

• several non-urological conditions that increase risk of bladder probs in older adults, such as:

• “DIAPPERS”

  • dementia, infection, atrophic vaginitis, pharmaceuticals, psychological, endocrine, restricted mobility, stool impaction

bladder cancer

• most bladder tumors are malignant and commonly arise from transitional epithelium of bladder

• often develops as multiple tumors

• diagnosed by urine cytology and biopsy

• early signs: ???

• tumor is invasive through wall to adjacent structures

  • metastasizes to pelvic lymph nodes, liver, and bone

predisposing factors of bladder cancer

• working w/ chemicals in labs and industry

• cig smoking

• recurrent infections

• heavy intake of analgesics

picture of bladder cancer