Summary BNF Chapter 7 - Genito-Urinary

URINARY INCONTINENCE

QUICK RECAP OF BLADDER PHYSIOLOGY:
- Urine produced by kidneys (collecting ducts) travels to bladder via ureters
- Size of bladder changes due to DETRUSOR MUSCLES:
o Muscles RELAX  bladder expands (holds more urine)
o Muscles CONTRACT  bladder becomes smaller (holds less urine)
- Men and women have the same sized bladder – but women store LESS URINE as
uterus prevents maximal enlargement of bladder

URETHRAL SPHINCTERS:
- As well as the detrusor muscles in the bladder,
muscular sphincters in the urethra also help
regulate urine control – TWO SPHINCTERS:
o Internal Sphincter: under
involuntary/ANS control
o External Sphincter: under
voluntary/skeletal muscle control (the
reason why you can stop peeing mid-stream)
- The external sphincter can be strengthened via KEGEL EXERCISES

URINARY INCONTINENCE (UI):
- Definition of UI: involuntary urination – can dramatically affect pts’ QoL
- There are different TYPES of UI:

1- Urge Incontinence: unexpected, sudden, intense urge to pee  slight leakage
- CAUSE: unexpected/involuntary contraction of detrusor muscle
2- Stress Incontinence: leakage only occurs when physical stress imposed on bladder
- CAUSE: physical abdominal stress (e.g. laughing, coughing, sneezing) is stronger
than the external urethral sphincter  forces out some urine
- PREGNANCY is another cause of stress incontinence
3- Overflow Incontinence: weak, intermittent urination due to difficulty passing urine
- CAUSE: anything which inhibits normal urine outflow (e.g. BPH, weak detrusor
muscles)  improper bladder emptying  bladder overflowing with urine 
incontinence

OLDER AGE is a RISK FACTOR for all types of incontinence




Important to establish type of
incontinence (i.e. the cause) – since
each type has its own TREATMENT

, TREATMENT OF URGE INCONTINENCE (i.e. ‘Overactive Bladder)

URINARY ANTIMUSCARINICS (1st Line) – Oxybutynin, Solifenacin, Darifenacin,
Trospium, Fesoterodine, Tolterodine
OVERVIEW:
- Work like all other antimuscarinics (e.g. in IBS, asthma/COPD, emesis)
- Have the SAME ADRs: dry mouth, constipation, blurred vision,
- ADR: Increased risk of UTI (as they promote urinary retention)
- CONTRAINDICATED in OVERFLOW incontinence/urinary RETENTION – AMs will
further weaken the detrusor muscles  even more urinary retention

Oxybutynin available as TRANSDERMAL PATCH – used where pts cannot tolerate oral form

When to NOT use AMs:
- Dementia/ Alzheimer’s (ACh is already low)
- Angle-closure/narrow-angle glaucoma (ACh helps promote AH drainage)
- Urinary retention/BPH (will make it worse)

MIRABEGRON – Betmiga (2nd Line)
MOA:
- Mirabegron is a ß3 selective AGONIST
- Stimulation of ß3 receptors on detrusor muscles has SAME EFFECT as AMs (bladder
relaxation)

SIDE EFFECTS:
- Same as AMs: dry mouth, blurred vision, urinary retention, UTI-risk
- Tachycardia & Hypertension: due to stimulation of sympathetic NS

BP needs monitoring BEFORE and DURING treatment w/ Mirabegron

TREATMENT OF STRESS INCONTINENCE – Kegel Exercises & Duloxetine

OVERVIEW:
- MOA: Duloxetine = SNRI – increases NA in CNS  stronger INTERNAL urethral
sphincter control  urine less likely to leak out when abdominal pressure applied
(does NOT affect voluntary urination)
- INDICATION: stress incontinence in WOMEN ONLY
- Same ADRs as other ADs: bleeding, weight gain, sexual dysfunction, hypertension
- AVOID ABRUPT WITHDRAWAL (esp if duration of use > 4 weeks) – abrupt
withdrawal  antidepressant discontinuation syndrome (ADS)

NICE GUIDANCE ON STRESS INCONTINENCE TREATMENT:
- 1st Line: Kegel Exercises (men & women)
- 2nd Line: Duloxetine (women only)