RENAL: Micturition and Incontinence Flashcards
What is the anatomy involved in micturition?
- Ureter
- Detrusor
- Urethral openings
- Trigone
- Urethra
(Prostate as well in males)
How does urine get from the kidneys to being excreted?
Processed tubular fluid dumpred by collecting system into renal pelvis, enters ureters:
- Renal pelvis - Collects urine from collecting ducts
- Ureters - Conduits that propel urine by peristaltic contractions toward the bladder
- Bladder - Muscular bag ‘holds’ urine and forces it out by contraction
- Urethra - Conduit for urine from bladder to outside
Describe micturition and identify its phases
Process of eliminating water and electrolytes from urinary system (urinating).
2 discrete phases:
- Storage/continence phase - Urine stored in bladder
- Voiding phase - Urine released through urethra
Phase require coordinated contraction/relaxation of bladder and urethral sphincters, controlled by sympathetic, parasympathetic and somatic nervous systems
Pons = where micturition centre controlled
Describe the storage phase of micturition
Storage:
- Requires relaxation of detrusor muscle of bladder, and simultaneous contraction of both internal urethral sphincters (IUS) and external urethral sphincters (EUS)
- Bladder and IUS under control of ANS. EUS under control of somatic nervous system. Means only EUS can be voluntarily opened or closed to control micturition, others contolled automatically
-
Sympathetic innervation:
- Signals sent to sympathetic nuclei in the spinal cord (nerve roots T10-L2) and finally to detrusor muscle and IUS. Impulses travel from spinal cord to bladder via hypogastric nerve (nerve roots T10-L2)
- At the bladder this stimulates the relaxation of the detrusor muscle in the bladder wall - via stimulation of B3- adrenoceptors in the fundus and the body of the bladder
- Contraction of IUS - via stimulation of alpha-1 adrenoceptors at neck of bladder
- Impulses travel to EUS via pudendal nerve (nerve roots S2-S4) to nicotinic (cholinergic) receptors on the striated muscle, resulting in contraction of EUS, prevents urine leaking out
- Coordinated relaxxation of detrusor muscle + contraction of urethral sphincters allows bladder to fill and store urine for many hours. As bladder fills, folds in bladder walls (rugae) flatten and walls distend, increasing capacity of bladder
Describe the voiding phase of micturition
Voiding of urine under parasympathetic control.
- Bladder afferent signals ascend through spinal cord, project to the pontine micturition centre and cerebrum. Upon voluntary decision to urinate, neurones of ponitine micturition entre fire to excite sacral preganglionic neurones
- Parasympathetic stimulation to pelvic nerve (S2-S4) causing release of Ach, works on M3 receptors on detrusor muscles, causes it to contract and increase intra-vesicular pressure. Pontine micturition centre also inhibits Onuf’s nucleus, with resultant reduction in sympathetic stimulation to IUS causing relaxation
- Conscious reduction in voluntary conduction of EUS from cerebral cortex allows for distension of urethra and passing of urine
Describe the reflex mechanism of micturition
- Bladder has smooth muscle called detrusor, when this contracts, bladder pressure increases
- Trigone on posterior wall has openings of the ureters (ureteric orifices)
- Bladder neck has muscle called IUS - Involuntary as long as urethral pressure is higher than the bladder pressure (continent is maintained)
- EUS is voluntary
- This reflex is an autonomic spinal cord reflex, under influence of higher centres (pons and supra pontine centres)
- Pontine micturition centre by default tries to trigger voiding reflex, cortex has an inhibitory influence on PMC until situation is appropriate for voluntary micturition, brain releases its inhibitory effect on the pons
- Contraction of abdominal muscles causes bladder pressure to rise, urine enters posterior urethra under pressure, stretch receptors get simulated followed by reflex resulting in contraction of detrusor, relaxation of internal sphincter and simulataneous relaxation of the external sphincter causing emptying
Pelvic - Pelvic nerves have sensory and parasympathetic fibres. Sensory fibres pick up stretch from stretch receptors as bladder fills. Parasympathetic nerves from sacral spinal cord (S2,3,4) act via Ach on M3, causes contraction of detrusor and relaxation of internal sphincter, parasympathetic system causes emptying of the bladder
Hypogastric - Sympathetic fibres fo via hypogastric plexus from L2 on spinal cord, act on B3 receptors on detrusor muscle. Relaxes detrusor muscle and effects on alpha 1 receptors of spinchter causes contraction. Sympathetic fibres are responsible for storage
Recall the transport of urine from the kidneys to the bladder
- Urine reaches bladder from calluses in kidney by ureter, urine streches the calyces and so produces peristalsis
- Ureter passes obliquely through detrusor muscle, during presistalsis the pressure in the ureter is high so keeps that portion open ensuring flow into the bladder
- When bladder fills, pressure on bladder rises, detrusor muscle compresses thar portion of ureter to stop backflow
Define incontinence
“Involuntary leaage of urine, may occur in patients with normal urinary tract as result of dementia or poor mobility, or transiently during an acute illness or hospitalisation, especially in older people”
Describe ICS defintions
- Increased Daytime Frequency - Complaint by patient who considers they void too often by day
- Nocturia - Individual has to wake at night one or more times to void
- Urgency - Sudden compelling desire to pass urine, which is difficult to defer
- UI - Complaint of involuntary leakage of urine
- SUI - Complaint of involuntary leakage on effort or exertion, or on sneezing or coughing
- UUI - Complaint of involuntary leakage accompanied by or immediately preceded by urgency
- MUI - Complaint of involuntary leakage associated with urgency and also with exertion, effort, sneezing or coughing
- OAB - Comprises of urgency with or without urgency incontinence, usually with frequency and nocturne inn the absence of pathology e.g. UTI
What conditions may cause bladder dysfunction?
- Age
- Pregnancy / Parity
- Obesity / BMI
- Systemic Oestrogen in women > 55 yrs of age
- DM?
- MUI=UUI > SUI re: bother
- Risk factor for falls, fractures, nursing home admissions
Describe how bladder dysfunction can be managed, medically and non-medically
Non-medical:
- Caffeine reduction (reduces daytime freqeuncy but not UI)
- Modify fluid intake, improves OAB but not UI
- Obesity associated with UI and weight reduction improves UI
Medically:
- Antimuscarinics such as Oxybutynin/Tolterodine
- Second line additional antimuscarinic
- Second/third line - Mirabegron (B3 agonist)
Surgically:
- Botulinum toxin A injections
- Urethral bulking
- Colposuspension
- Male sling/AUS (artificial urinary sphincter)
Describe the actions of antimuscarinic medications
- Antagonism - Bind to M3 receptors, prevents binding of Ach, therefore prevents contraction of detrusor muscle.
- Antagonism of M2 receptors may prevent contraction of smooth muscle in the bladder
- Mirabegron works by activating the B3 adrenergic receptor in the bladder, resulting in its relaxation
What are some risk factors for UTIs?
- Pregnancy.
- Obesity.
- A personal or family history of urinary tract infections.
- Using spermicide and/or a diaphragm as birth control.
- Having frequent sexual encounters.
- Urinary incontinence.
- Sexually transmitted infections.
- Enlarged prostate.
What are the causes of kidney stones and what is the aetiology of them?
- Dehydration - due to low urine - higher calcium oxalate supersaturation in urine, high protein intake, high salt intake, obesity, male sex, some precipitant medications such as antacid (calcium containing)
- 80% calcium oxalate
- 20% calcium phosphate- risk factors include low urine volume, hypercalciuria, high urine pH, primary hyperparathyroidism and RTA (renal tubular acidosis)
- 10-20% uric acid stones due to urinary PH <5.5
- 1% Cystine stones inborn error of metabolism , cystinuria, autosomal recessive disorder that results in abnormal renal tubular reabsorption of amino acids
- 5-10% struvite stones- “infection stones”- comprised of magnesium, ammonium and phosphate. Frequently present as staghorn calculi and are associated with organisms such as proteus, pseudomonas and klebsiella.
What are symptoms of kidney stones?
- Acute severe flank pain
- Nausea + vomiting
- Urinary frequency/urgency
- Haematuria
- Testicular pain (loin to groin pain)
Stone location and pain innervation:
- Upper ureter and renal pelvis - Pain from upper ureteric stones radiates to flank and lumbar areas
- Middle ureter - Radiates anteriorly and caudally
- Distal ureter - Tends to radiate into groin or testicle/ labia majora in females because pain is referred from ilioinguinal or genitofemoral nerves
PMH (Past medical history)
- Previous stonesHypercalcaemia – hyperparathyroidism * Family history
- Differential diagnosis - AAA in elderly
OTHER differentials
Appendicitis, biliary colic, ischaemic bowel, sigmoid volvulus,
Ectopic pregnancy, diverticulitis, renal vein thrombosis, ovarian abscess, discitis,
How can kidney stones be diagnosed?
- Urine dipstick - Presence of blood
- Imaging - Non contrast CT, Ultrasound if pregnant - This is needed to confirm presence of stone
How can kidney stones be treated?
Depends on size, location and the patient
- Size - L + W, <5mm, >90% chance of passing but if >7mm, unlikely to pass
- Site of stone - Kidney/ ureter. Ureted divided into 3 by sacrum, if in upper portion, unlikely to pass
Treatment:
- Pain relief - NSAID - diclofenac 150mg PR (lasts approx 18 hrs) - Much more efective than morphine
Admit when:
- Incontrolled pain
- Solitary kidney
- Pyrexial - Patient would need antiobiotics and fluid resuscitation
- Bilateral ureteric stones (rare)
- Admit all patients with temperature
