40. Micturition Flashcards
What is the basic anatomy of the micturition system?
Where is the micturition centre?
Explain how the micturition reflex works.
2 inlets (ureters), store and pump (bladder), outflow (urethra), restrictor (spinchter)
Pons
Stretch receptors in bladder start triggering as bladder fills -> sensory feedback to brain micturition centre. When ready to urinate: somatic response to sphincter via S2-4 (pudendal nerve) and open sphincter, and reflex action via parasympathetic S2-4 squeezes detrusor muscles = urinate. Sphincter closes after emptying.
Explain the 2 phases of the bladder cycle.
What is normal bladder contraction caused by?
List 3 main categories of lower urinary tract symptoms.
1) Storage phase: detrusor relaxes, urethra and pelvic floor contract. Cells slide over each other = bladder expands, low pressure but slowly rises
2) Emptying phase: detrusor contracts, urethra and pelvic floor relax, micturition
Release of ACh from cholinergic nerves, stimulation of muscarinic receptors on detrusor SM
Storage (irritative) e.g. nocturia, urge incontinence, voiding (ostructive) e.g. hesitancy, poor flow, straining, incomplete emptying, overactive bladder syndrome (urgency +/- incontinence)
How would you diagnose a lower urinary tract problem?
What preliminary exam can you give someone with suspected prostate problems?
What investigations could you do for someone with urinary problems?
Medical and personal history, past medical history, physical examination (inc. rectal exam to check S2-4). How bad is it?
International Prostate Symptom Score - questionnaire. Mild 0-7, severe 20-35.
Urine dip, FBC/U+E/PSA, uroflometry and post void residual volume (flow rate decreases with age), urodynamics, ultrasound KUB, CT KUB, nuclear imaging
If the micturition system comprises an outlet, pump, constituents and control mechanism, what problems could befall each component?
What is BPH?
Outlet: bladder neck, prostate, strictrure, meatus, foreskin
Pump: bladder (OAB, sensory, failure), cardiac, medications
Control: neurology (stroke, spina bifida, cord injury, MS, tumour, parkinsons)
Constituents: UTI, cancer, inflammation, stones
Benign prostatic hyperplasia: benign nodulation or diffuse proliferation of musculofibrous and glandular layers of prostate. Inner transitional zone enlarges in contrast to peripheral layer expansion seen in prostate carcinoma. Obstructed urinary flow.
How is BPH managed conservatively (first)?
How is BPH managed medically?
What surgery is availble for lower urinary tract symptoms (LUTS)?
Lifestyle advice: fluid (type, amount)(use voiding diary), food, smoking (direct irritation), bladder drill (retrain to go every 3-4hrs), urethral milking, pads and convenes. CATHETERS = LAST RESORT!
Alpha blockers (stretch SM, allow more urine through e.g. tamsulosin, alfuzosin), 5-α reductase inhibitors (shrink prostate e.g. finasteride), PDE5 inhibitors, antimuscarinics (for OAB), combination
TURP (gold standard, electric loop carves out prostate chips), HoLEP/greenlight (laser operation - tissue removal), Urolift (staples to hold prostate away from urethra to keep it open).
What are the features of an ‘overactive bladder’?
Explain the 3 types of urinary incontinence?
What are the treatments for this?
Urinary urgency (+/- incontinence), urinary frequency, sometimes nocturia
Stress (leakage on effort/exertion), urge, mixed (most). Normally pelvic floor supports everything when e.g. cough, but with stress incontinence = this support is lost and urine can leak out. Urge = bladder overactive and can produce more pressure than sphincter can cope with
Always treat overactive component first. Conservative measures (fluid intake, caffiene and stimulants, pads), pelvic floor exercises, tablets, post. tibial/sacral nerve stim, botox, surgery
List some medications for OAB/urge incontinence.
What other treatments are there for urinary incontinance?
Anticholinergics (e.g.oxybutnin): block ACh in parasympathetic nerves = calms bladder (SE - block elsewhere too like salivary glands)
β3 adrenergics (e.g. mirabegron): β3 adrenoreceptors upegulated in OAB (SE = hypertension)
Botox A: fuses synaptic visicles with motor end plate, paralyses bladder
Pads, fluid intake, treat OAB, pelvic floor exercises, vaginal cones, mid urethral slings
Explain how lesions in different areas can affect the bladder or not (the neurogenic bladder).
Lesions above pontine micturition centre are ‘safe’ (CVA, parkinson’s, brain injury, MS)
Lesions below T12 are safe, as bladder and sphincter are flaccid and low pressure (trauma, tumours, spina bifida)
Lesions in between are unsafe - uncoordinated, and thus high pressures in the resting bladder result (RTA, tumours, MS)
