Urology - Urinary Retention Flashcards
Urinary Retention: causes - obstructive
- Mechanical: BPH, urethral stricture, clots, stones, constipation
- Dynamic: increase of SM tone (alpha adrenergic), post op pain and drugs
Urinary Retention: causes - Neurological
-Interruption of sensory or motor innervation: pelvic surgery, MS, DM, spinal injury/compression
Urinary Retention: causes - Myogenic
-Over distension of bladder: post op anaesthesia or high alcohol intake
Outline the vasculature of the bladder
- Main vasculature from internal iliac vessels, via superior vesicular branch
- Males: supplemented by inferior vesicular
- Females: supplemented by vaginal arteries
- Both sexes: obturator and inferior gluteal arteries contribute small branches
- Venous drainage: vesicular venous plexus, which empty into internal iliac vein
Outline the lymphatics of the bladder
- Superolateral aspect: external iliac
- Neck and fungus: internal iliac, sacral and common Iliac
Outline the nervous supply of bladder
- Relaxation of detrusor muscle: sympathetic NS via hypogastric nerve (T12-L2) - promotes urine retention
- Contraction of detrusor: parasympathetic NS via pelvic nerve (S2-S4) - stimulates micturition
- Voluntary control of external urethral sphincter: somatic NS via pudendal nerve (S2-S4) - can cause voluntary constriction (storage) or relaxation (voiding)
Outline the bladder stretch reflex (when is it important in adults?)
- Primitive spinal reflex - overridden in potty training
- Bladder fills and stretches walls - detected by sensory nerves and transmitted to spinal cord
- Interneurones within spinal cord relay signal to parasympathetic efferent (pelvic nerve)
- Pelvic nerve acts to contract detrusor and stimulate voiding
- Must be considered in spinal injuries (descending inhibition can’t reach bladder) and neurodegenerative diseases (brain can’t generate inhibition)
Spinal cord injuries and bladder: above T12
- Afferent signals from bladder wall can’t reach brain t/f pt has no awareness of bladder filling
- Also no descending control over EUS t/f constantly relaxed
- this is functioning spinal reflex - parasympathetic NS initiates detrusor contraction in response to bladder wall stretch t/f bladder empties as it fills
Spinal cord injuries and bladder: below T12
- lesion at this level will damage parasympathetic outflow of bladder - detrusor is paralysed and can’t contract
- spinal reflex doesn’t function
- bladder fills uncontrollably and leads to overflow incontinence
Acute Urinary Retention: clinical features
- Suprapubic tenderness
- palpable bladder (dull to percussion)
- Large prostate on PR (check anal tone and sacral sensation)
- should drain <1L on catheterisation
What medications can cause acute urinary retention?
- Anticholinergics, benzodiazepines, TCAs and Antihistamines: act to inhibit the parasympathetic drive on detrusor muscle
- Opioids: Mu receptor agonism lead to increased sphincter tone and urinary bladder via sympathetic overstimulation (results in increased bladder outlet resistance)
Acute Urinary Retention: Ix
- Bloods: FBC, U&E, PSA (prior to PR)
- Urine: dip, MC + S
- Imaging: Us bladder (volume and hydronephrosis) + Pelvic XR
Acute Urinary Retention: Mx - conservative
- Analgesia
- privacy
- walking
- running water/hot bath
Acute Urinary Retention: Mx - non conservative
- Catheterise: TWOC after 24-72 hours
- TURP: if failed TWOC, impaired renal function or can be elective
Chronic Urinary retention: High pressure
- High detrusor pressure at end of micturition
- typically caused by bladder outflow obstruction
- causes bilateral hydronephrosis and decreases renal function
