Urinary Tract Function & Infection Flashcards
What is the definition of the lower urinary tract?
Lower urinary tract definition – bladder and urethra
In males this refers to the anterior urethra (penile urethra and bulbar urethra), posterior urethra (membranous and prostatic urethra) and the bladder itself
What is the definition of the upper urinary tract?
Upper urinary tract – bilateral ureters and bilateral renal collecting systems
What structures protect the lower urinary tract?
LUT is protected by fascial layers and some protection from bone (pubic rami anteriorly and posteriorly by the iliac wings)
How does the detrusor muscle in the bladder differ between males and females?
Thicker detrusor muscle in males – males need to work hard to overcome the resistance provided by the prostate gland
What are the roles of the urothelium, lamina propria and detrusor muscle in the wall of the bladder?
Different layers with different roles
Urothelium – barrier function and afferent signaling
Lamina propria – functional center that coordinates the signals from the urothelium and detrusor muscle – blood vessels, nerves and myofibroblasts pass through here
Detrusor muscle stroma – smooth muscle arranged in bundles, functional syncytium (cells fused), stroma – consists of collagen and elastin, innervation of muscle by the postganglionic parasympathetic system
Why do tight junctions between epithelial cells in the bladder play an important role?
Apical membrane with tight junctions – important for signaling for bladder filling/stretching – signals relayed onwards to allow for bladder voiding
What are the normal functions of the bladder?
Three main roles
- Compliant reservoir for urine
- Barrier function (GAG layer/tight junctions) - prevent leakage of urine (but not truly waterproof) – damage to the urothelium plays a role in disease
- Volitional voiding – muscular function to remove urine
How does the bladder pressure stay constant despite increases in volume?
Bladder pressure remains constant despite increase in volume
Bladder is highly compliant due to visco-elastic properties (elastin/collagen; detrusor relaxation
without change in tension)
How is the level of bladder filling detected?
Bladder filling stretch sensors detect increase in wall tension
Afferent neurons send signals to the dorsal horn of the sacral spinal cord, which relay signals to the higher centers and brainstem – real time data – allows for control of bladder
From a neurological perspective, how is urine voiding controlled?
Urine voiding is controlled by the spino-bulbar reflex
But it is modulated by the pontine micturition centre (Barrington’s nucleus) in the brain (pons) - allows for voiding to occur on socially acceptable times.
And further processing taking place in the Onuf’s Nucleus (sacral level - S2, S3 and S4)
When is normal and uncomfortable bladder fullness detected?
Bladder fullness is detected at 250ml and uncomfortable at 500ml
What coordinated action between the baldder and sphincters for voiding to take place?
During voiding – coordinated action of detrusor contraction and urethral sphincter relaxation – allows urine to enter the posterior urethra allowing voiding to occur
What is the positive feedback loop that helps drive micturition?
During voiding itself – positive feedback loop
Detrusor contracts – wall tension rises – afferent signals to PMC – processes these – strengthens contractions with efferent signals
What are the two nerves responsible for driving detrusor contraction and sphincter relaxation?
Pelvic nerves - detrusor
Pudendal nerves - sphincter relaxation.
Explain what this diagram is showing.
Normal neurophysiology
Bladder filing - Afferent signals from stretch receptors sent to the sacral spinal cord – sent up to the higher centers (pons and other areas) – sends efferent signals back down and if the bladder is sufficiently full this will lead to volitional voiding – leads to coordinated detrusor muscle contraction and sphincter relaxation via the pelvic nerves and the pudendal nerves
Overall reflex arc is under control of higher centers - mainly the PMC
Bladder is subject to facilitation (contraction of detrusor and relaxation of sphincter when the bladder is less than full) and inhibition (postponement of voiding) – external factors
What are some neurotransmitters/molecules involved in regulating bladder activity?
Numerous neurotransmitters involved
- Excitatory - Cholinergic + Role of nitric oxide in the relaxation of the bladder neck and external urethral sphincter
- Inhibitory – GABA and glycine
What happens to the neurological control of bladder function if we get a spinal cord injury?
Spinal bulbar reflex arc is modulated by higher centers – spinal cord injury results in loss of central inhibition – results in control of voiding by the spino-bulbar-arc (parasympathetic nerves and pudendal nerves)
How does damage to the suprapontine, spinal and sacral regions influence bladder function?
How a patient presents depends on the level where the injury has taken place
Suprapontine – storage symptoms – experience urgency and frequency to pass urine, they pass urine completely (no residual) but have detrusor overactivity
Spinal – both storage and voiding (poor intermittent urinary flow) + PVR (post-voiding residual urine) is raised – don’t empty to completion, detrusor overactivity and dyscoordination between detrusor muscle and the sphincters
Sacral – voiding symptoms, PVR is raised and urodynamics – hypocontractile or acontractile detrusor
On average, how frequently do people urinate and how much do they urinate (volume) when they do go?
Bladder responsible for STORAGE of urine
When the bladder contains c. 300mls (and it is socially convenient) VOIDING is initiated.
Normal voiding pattern - 300-400mls per void, 4-5 per day (less than 7) - depending on input
No urgency or incontinence.
What two ways do we use to collect data on someone’s bladder function?
Patients coming to clinic – void to frequently or at night
In this case we use a volume and frequency chart or a bladder diary to understand what’s happening in more detail
What is a frequency/volume chart?
Frequency and volume chart – frequency and volume – gives us information on frequency, functional capacity and nocturia (when) – but no info on intake!
What is a bladder diary?
Bladder diary – monitors inputs (volume ingested, type of fluid and when) as well as outputs (frequency, functional capacity and voiding at night)
Can pick up on important information such as…
* Drinking at night – resulting in nocturnal diuresis
* Wet UI episodes – incontinence episodes
What are storage lower urinary tract symptoms?
STORAGE LUTS:
1. Urgency
2. Frequency
3. Nocturia
4. UI: urinary incontinence
What are voiding lower urinary tract symptoms?
VOIDING LUTS:
1. Hesitancy
2. Poor flow
3. Intermittency
4. Terminal dribbling
What might be causing storage LUTs (increased frequency, urgency and nocturia)?
Storage LUTS – frequency urgency and nocturia
Reflects…
1. Increased urinary production (excess urine output or fluid intake)
2. Decreased capacity - reduced compliance or functional capacity - results from irritation (bladder stones or tumour) or neurogenic bladder (MS - early emptying)
What is normal nocturnal frequency? What are reasons why it might increase?
Nocturia – nocturnal frequency - less than 2x night
Reasons - ageing bladder, BOO (bladder outflow obstruction), bladders with reduced compliance (expansion) and dietary habits
Why do we see increase nocturnal urination as we age?
Effect of ageing – renal concentrating ability decreases (e.g. less salts reabsorbed) which increases urine output
Patients with peripheral ankle oedema (cardiac/renal failure - more common with age) - we see increased renal blood flow at night when patients are laying flat in turn increasing urine production
Nocturia is important cause it can increase the risk of falls
What is the definition of nocturnal polyuria?
Nocturnal polyuria – production of more than one third of 24-hour urine output between midnight and 8am
Whats a uroflowmeter?
UroFlowMeter looks at…
Look at voiding volume
Maximal urinary flow rate
Voiding time
Bladder scan can be used to look for residual volume – over 200ml is significant
Explain the different parts of this normal urodynamics trace.
Normal looking urodynamics trace
Equipment - urethral catheter, intra-vesicle pressure transducer and pressure transducer in the rectum
Trace divided into the Filling and voiding phase
Intravesical pressure – abdominal = detrusor pressure
Filling phase – saline solution is introduced into the bladder at a constant rate (blue trace at the bottom)
* Detrusor pressure is low – while filling – indicates that the bladder has a compliant bladder
* When they cough (shown by abdominal increases in pressure) there is no urinary outflow (no stress urinary incontinence)
* No detrusor activity in the filling phase (no overactivity present)
- Voiding phase – remove urethral catheter + transducers remain + patient is asked to void
- Rise in intravesical and detrusor pressure – resulting in urinary outflow – normal function in this case
What does the following urodynamics trace show? What would the patient benefit from?
Patient with unstable bladder – detrusor overactivity with detrusor overactivity incontinence – benefit from anti-muscarinic therapy or botox therapy for the bladder.
Filling phase – see spontaneous detrusor pressure in the filling phase – evidence of overactivity
Coughing – rise in abdominal pressure – no urinary flow present – no stress incontinence
Voiding phase – rise in intravesical pressure – results in urinary flow – no evidence of obstruction of flow
What does the following urodynamics trace show?
Patient with stress urinary incontinence with a normal compliance bladder - coughing (abdominal pressure rises) coincides with urinary outflow – stress incontinence
What’s going on in the followign urodynamics trace?
Bladder outlet obstruction
* No unstable contractions during filling
* No leak whilst coughing during filling
* Very high pressure and low flow during voiding
What are the risk factors for an uncomplicated UTI?
Normal urinary tract with no immunocompromise - uncomplicated
Who gets complicated UTIs? What are the risk factors?
Complicated - Compromised Urinary tract or host defenses
Flow of urine outwards is important for preventing UTI – prevents stagnant urine
Risk factor for the development of sepsis
What organisms are most commonly responsible for UTIs?
Gram positive – thick cell wall – live on dry places of the body – Staph and strep
Gram negative – thin cell wall – live in more wet environments – E. Coli (UPEC) and pneuonmiae – main cause of UTIs
Where do the bacteria for UTIs commonly come from?
Periurethral contamination from gut/anus to the urethral opening – distance from anus and urethra is predictive for UTIs
Illustration - shows how infections can move up the bladder into the kidney and potentially into the blood stream
How can bacteria infect the bladder wall?
Infection of epithelial membrane using type 1 pili – grow and multiply and burst out – infecting more cells
Bacteria can go deeper down into deeper layers of the epithelium – lay dormant (immune system can find them and away from antibiotics) – potential theory for recurrent UTIs
To cause pyelonephritis bacteria must express pyelonephritis associated (P) pili
What are some virulence factors that bacteria have to help them with infection?
What host factors do we have to help prevent infection?
Host defenses
* Urine has a low pH and high urea – should be protective against infection
* Urine flow prevents infection
* Mucosa – protective layer
* Inhibitors against adherence
* Normal inflammatory defense
What should you be asking about when taking the clinical history?
Clinical history
* Where is dysuria?
* Menstrual history
* Sexual history
Long list of things that cause dysuria – make sure you exclude these other factors – especially for recurrent cystitis
What is some simple advise we can offer in cases where people suffer from recurrent UTIs?
