Kidney Physiology, Micturition and LUTS Flashcards
What are the functions of the kidney?
1 - Water and Hormone homeostasis (H+, Na+, K+, PO4-, others)
2 - Filters the blood - removal of toxins and waste and retains proteins (Albumin & creatinine) and macros from excretion
3 - Endocrine Function
4- Urea Production
What are the endocrine functions of the kidney?
Renin - regulates blood pressure and water levels
Kallikrein - coagulation
EPO - RBC Production
Calcitriol - Final activation of vit d3
What are the associated LUTS - lower urinary tract symptoms?
STORAGE Issues
~ FUNI - ‘need to pee’ / spinal lesion
Frequency
Urgency
Nocturia
Incontinence
VOIDING Issues
SHID - outflow obstruction
Occurs
Poor Stream
Hesitancy
Incomplete emptying
Dribbling
What is Micturition ?
Micturition is the process of eliminating water and electrolytes from the urinary system
URINATING
Has two phases: Storage (continence) and Voiding
Describe the neural network behind micturition?
Bladder detrusor muscle and Internal urethra sphincter IUS are autonomously controlled:
Storage is controlled by SNS activation via hypogastric nerve (T10-L2)
Voiding is controlled by PNS activation via pelvic (S2-S4)
External urethra Sphincter EUS is somatically (voluntary) control via pudendal nerve originating at ONUF’S nucleus (S2-S4)
Afferent sensory nerves run via pelvic nerve
Describe the neural pathway involved in storage
Filling stage:
Pontine continence centre (left side pons)->sympathetic nuclei in spinal cord (T10-L2) ->VIA HYPOGASTRIC NERVE impulse sent to the bladder =
o via alpha1 R – contraction of IUS
o via alpha3 R – Relaxation of detrusor wall
Voluntary control of EUS
Cortex -> Impulse travel to the EUS via pudendal nerve (S2-S4) to nicotinic (cholinergic) receptors = contraction of EUS
What is “receptive relaxation” / stress relaxation?
Coordinated effect controlled by Pontine micturition centre
As the bladder fills -> folded bladder walls (rugae) distend and flatten
= Maintains constant pressure in the bladder
Describe the neural pathway involved in voiding
Micturition reflex
When ~400ml present in bladder -> afferent signal impulse via pelvic nerve to sacral micturition centre and then up to PMC triggering PNS reflex response:
PNS: PMC->SMC->Pelvic Nerve-> Nictonic M3-Detrusor muscle = Contraction
PMC also inhibits Onuf’s nucleus= less SNS
= Less bladder wall relaxation and less sphincter contraction
Somatic response: CONSCIOUS REDUCUCTION in voluntary contraction of EUS = relaxation of EUS allowing urine passing
What happens if you shouldnt pee?
If inappropriate to void – Guarding reflex:
* Sympathetic (hypogastric) nerve stimulation results in detrusor relaxation
* Pudendal nerve stimulation results in contraction of the external urethral sphincter
* inhibiting involuntary bladder emptying
What can cause voiding issues?
Usually Obstruction to urine flow caused by:
BPH
Nerve dysfunction
Infection
Drugs - Anti-cholinergic, Opioids
Tx - Urinary Catehrisation
What can cause storage/continence issues?
Spinal cord lesion above T12 (Reflex bladder)
What are the different types of continence issues?
- Stress incontinence – urine leakage when pressure is exerted on the bladder.
(Pregnancy, laughing, sneezing, ~High Abdo pa) - Urge incontinence – urine leakage as soon as the urge to urinate arise. (~UTI, caffeine, alcohol)
- Overflow incontinence – urine leakage due to the bladder being overfilled. (Bladder stone / Chronic urinary retention)
- Neurological incontinence – urine leakage caused by nerve lesions PCC lesion, Above T12 lesion or neurological conditions, such as multiple sclerosis or spinal cord compression
How to treat incontinence
Treatment
* Anticholinergics – block PNS activated contractions of bladder wall OXYBUTYNIN
* B3 adrenoreceptors agonist – stimulates bladder wall relaxation MIRABEGRON -
