Renal& UTIs Flashcards
What anatomical feature in females means UTIs are more common?
Shorter urethra
What are the host factors contributing to UTIs?
Shorter urethra
Obstruction - enlarged prostate, pregnancy, stones, tumour
Neurological problems - incomplete emptying, residual urine
Ureteric reflux - ascending infection from bladder esp in children
WHere are common sites of urinary tract obstruction?
PUJ: calculi Ureter: Calculi, Ca, retroperitoneal fibrosis Bladder: Neuropathic bladder VUJ: calculi Bladder neck: hypertrophy Prostate: BPH/Ca Urethra: stricture
What are the bacterial factors of UTIs?
Fimbrae allow attachment to host epithelium
K antigen permits production of polysaccharide capsule
Urease breaks down urea creatinga favourable environment for bacterial growth
Haemolysins damage host membranes and cause renal damage
What are the clinical syndromes of a UTI?
Frequency and dysuria (lower UTI) Acute pyelonephritis (upper UTI) Chronic nephritis Asymptomatic (pregnancy many problems for mother and baby) Septicaemia +/- shock
What are the signs and symptoms of a lower UTI?
Low grade fever
Dysuria
Frequency
Urgency
What are the signs and symptoms of an upper UTI (pyelonephritis)?
Fever
Loin pain
May have dysuria, frequency
When are investigations of UTI needed?
Healthy women - ‘uncomplicated UTI’ no need to culture urine - nitrite/leucocyte esterase dipstick testing
Culture urine in ‘complicated UTI’ ie pregnancy, treatment failure, suspected pyelonephritis, complications, male, paediatric
How might a specimen be collected to investigate a UTI further?
MSU - cleansing not required in women Clean catch in children - no antiseptic Collection bag (20% false positives) Catheter sample Supra-pubic aspiration
How is a specimen for UTI investigation transported?
4 degrees C +/- boric acid - disolves in the urine, stops the microorganisms multiplying -> accurate results
What can be tested in a urine sample?
-Turbidity (visual inspection) DIpstick testing can detect: -Leucocyte esterase -Nitrite -Haematuria -Proteinuria
What cells will be present in a urine sample of a patient with a UTI under the microscope?
Acute - WBC and RBC
Contaminated urine - squame (epithelial cells) NOT indication of UTI
Why is a nitrite test specific but not sensitive for UTI investigation?
Specific - if nitrites present in sample, definite positive test for UTI
Sensitive - Not all bacteria produce nitrites therefore not all UTIs will produce nitrite positive test
What might make a urine culture tray turn pink?
Lactose fermentors change pH
How many colonies distinguishes bacteriuria and when is this useful?
> 10^5 cfu/ml
Asympomatic females compared with femals with pyelonephritis
What is the role of a culture of urine?
Investigation of children, males and comlicate infections Increased sensitivity Epidemiology of isolates Susceptible data Control of specimen quality
What needs to be taken into account in interpretation of a culture report for a UTI?
Clinical details - symptoms/previous antibiotics Quality of specimen Delays in culture Microscopy (if available) Organism(s) isolated
What other problems may be the cause of urethral syndrome?
Low bacteriuria Fastidious organism Vaginal infection/inflammation STI - urethritis Mechanical, physical and chemical causes
When would imaging of the urinary tract be used?
All children
Males - posterior urethral valves
Females - vesico- ureteric reflux
What might sterile pyuria be indicative of?
Antibiotics Urethritis Vaginal infection/inflammation Chemical inflammation TB Appendicitis Fastidious organism?
What is the treatment of a UTI?
Increases fluid intake
Adress underlying disorders
3 day antibiotics if uncomlicated, 5 if complicated
CSU only if symptomatic - likely false positive as it is another medium for bacteria to colonise
What is the treatment of simple cystitis?
Uncomplicated infections can be treated with trimethoprim or nitrofurantoin.
3 day course as effective as 5/7 os use minimal to reduce resistance
What antibiotics are used for complicated UTIs?
Trimethoprim, nitrofurantoin or cephalexin
Amoxicillin not appropriate as 50% resistant
How is pyelonephritis/septicaemia treated?
14 day course
Agent with systemic activity
Possibly IV initially unless good PO absorption and patient well enough
Co-amoxiclav, ciprofloxacin, gentamicin (IV only - nephrotoxic)
Why is ciprofloxacin rarely used anymore?
Commonly results in C. diff
When would prophylaxis be given to a patient for UTI?
More than 3 episodes in 1 year
No treatable underlying cause
Trimethoprim or nitrofurantoin - single nightly dose
What are the problems of prophylaxis for recurrent UTIs?
Resistance builds
Expensive
What is diuresis?
Increased formation of urine by the kidney
What is a diuretic?
A substance that promotes a diuresis -> reduction in ECF volume. Increase fraction excretion of sodium by blocking reabsorption
When are diuretics used?
Conditions with ECF expansion and oedema
Acute pulmonary oedema
Hypertension
(Na and water reabsorption too high)
As well as blocking ENaC in the luminal membrane of the DCT and CD, what else do diuretics do here?
Reduce K+ secretion - disruption of electrochemical gradient
What diuretics are used?
- Direct action on cells to block Na+ transporters in the luminal membrane
- By antagonising action of aldosterone
- Thiazide diuretics
- K+ sparing
- Modification of filtrate content - osmotic diuretics
- Inhibition of carbonic anhydrase inhibitors (no longer used as diuretic)
What diuretics work on the DCT?
Thiazide diuretics
Metalozone
Indapimide
What type of diuretics are used on the late DCT and CD?
K+ sparing diuretics
Aldosterone antagonists
How do antagonising aldosterone diuretics work?
Inhibits aldosterone action on principle cells of late DCT and CD reducing Na reabsorption. Competitive inhibition
How do osmotic diuretics work?
Increase osmolarity of filtrate by reducing reabsorption out of tubule
How could carbonic anhydrase inhibitors be used as a diuretic?
Acts on PCT inhibiting carbonic anhydrase interferes with Na and HCO3- reabsorption -> can cause metabolic acidosis
Useful in treatment of glaucoma -> reduces formation of aqueous humor in eye by about 50%
Where do loop and thiazide diuretics enter the tubule?
PCT via organic anion pathway -> travel downstream to loop/DCT
Why are loop diuretics so potent?
25-30% of Na reabsorbed in loop
Segements beyond have limited capacity to reabsorb the resulting Na and H2O
When are loop diuretics used?
Heart failure Treat flui dretention and oedema in: - nephrotic syndrome - renal failure - cirrhosis of liver Impairs calcium absorption in the loop of henle - useful to treat hypercalcaemia
How do thiazide diuretics work?
Block Na-Cl transporter in DCT. Less potent than loop, less Na reabsorption in DCT
When are thiazide diuretics used?
Hypertension (vasodilation
What problems are associated with thiazide diuretics?
Hypokalaemia (also associated with K sparing diuretics)
esp if used with ACE inhibitors, K supplements or in patient with renal impairment
What is the best drug treatment of hypertension due to primary hyperaldosteronism (Conn’s syndrome)?
Aldosterone antagonists
Also used for ascites and oedema in cirrhosis and in addition to loop diuretics in heart failure
How does mannitol work as an osmotic diuretic?
Small inert molecule
Increase plasma osmolarity thus drawing out fluid from tissues and cells
Freely filtered at the glom. but not reabsorbed -> increases osmolarity of filtrate
Acts by altering the driving force for renal absorption (osmolarity)
Loss of water, Na and K
When is oedema common?
Congestive heart failure - increase in venous pressure. Drop in CO causes activation of RAAS
Nephrotic syndrome
Cirrhosis of liver
Kidney failure
How does nephrotic syndrome cause oedema?
Protein los in urine Low plasma albumin Low oncotic pressure -> oedema Reduced circulatory vol RAS activated Na and H2O retention Expansion of ECF and oedema
How does cirrhosis of the liver cause oedema?
Less albumin production in liver so low in plasma
Low oncotic pressure -> oedema
Reduced circulatory volume
RAS activated
Na and water retention -> expansion of ECF and worsening oedema
How does liver cirrhosis cause ascites?
Portal hypertension -> increased venous pressure in splanchnic circulation (high venous pressure + low oncotic pressure ->ascites)
Reduced circulatory volume activates RAS and Na and water retained causing expansion of ECF and worsening oedema
What alternative uses do diuretics have?
Hypercalcaemia treatment - loop diuretics
Mannitol used in cerebral oedema
Treat glaucoma with carbonic anhydrase inhibitors
Define micturation.
To want to pass urine
Define detrusor
To push down
What controls micturation?
The spinal cord
What are the functional divisions of the bladder?
Body - Temporary store of urine
Trigone - ureteric orifices and internal urethral orifice are at angles of a triangle
Neck - Connects bladder to the urethra
What are the 3 major muscles in the bladder?
Detrusor urinae
Internal urethral sphincter
External urethral sphincter (formed by pelvic floors)
Describe arrangement of the detrusor muscle.
Formed from a plexiform meshwork of smooth muscle fibres
Appear in random distribution in orientation in cross section but actually in 3 layers - inner longitudinal, middle circular, outer longitudinal
Strength
What type of neural supply supplies the detrusor urinae muscle?
Bilateral (left and right sides of the spinal cord)
Various anatomical components of the bladder are supplied by different divisions of the nervous system -> disorders can be varied and complex
Autonomic symp and para
Not voluntary control
What nervous supply is the external urethral sphincter?
Somatic. Voluntary control from cerebral cortex via the spinal cord
Why are neuronal disorders of the urinary bladder very complex?
Spinal lesions controlling the bladder disturbs the ordered co-operation between the somatic and autonomic divisions of the nervous system
Can be life threatening
What are the characteristics of the detrusor muscle?
Classified as smooth muscle A mass of contracting muscle Has no peristaltic activity Lined with transitional epithelium Epithelium of bladder is non-secretory Same form and size in both sex Found in the true pelvis
What are the general functions of the urinary bladder?
Temporary storage of urine
Expulsion of urine
What is the continence phase?
Storage of urine
What results from neuronal apparatus damage?
Failure to store urine resulting in reduced bladder capacity, hence very frequent passing of urine - incontinence
What is the micturation phase?
Voiding function of the urinary bladder
Damage to neurones that promote micturation will lead to failure to pass urine voluntarily resulting in urine retention. Urine is then only passed by an overflowing bladder
Describe the coordination of neural control required to pass urine.
Bladder and external urethral sphincter must coordinate. Bladder relaxes, sphincter contracts. Bladder contracts, sphincter relaxes
Disturbances in this synchrony leads to detrusor-Sphincter dussenergia
What are continence circuits?
Neural apparatus prescribing for urinary storage
What is the capacity of the bladder?
approx 550ml (300-700 sometimes up to 1L)
What is monitored in the bladder?
Urine ionic composition, temp, volume by sensory neurones in submucosa
How is continence controlled?
Sympathetic
Cerebral cortex -> Pontine continence or storage centre (L-region) -> Sympathetic nuclei in cord -> Detrusor muscle and sphincter motorneurones in sacral cord
What receptors bring about relaxation of the detrusor muscle?
Beta 3 in the funds and body of bladder
What receptors increase the urethral sphincter pressure?
Alpha adreno in neck
What branch of the nervous system activates closure of the external urethral sphincter?
Somatic
What are the root values of the sympathetic nervous system?
Thoraco-lumbar - T10/12 - L2
Derived from lumbar splanchnics
T10-12 terminate in the inferior mesenteric ganglion
L1 and 2 terminate on neurones of the hypogastric plexus or presacral nerves
Where does the somatec nervous system originate from?
Onlufs nucleus of the ventral horn of the cord
S2-4
What are the folds in the bladder known as?
Rugae
What are the mechanical events during continence and storage?
Internal urethral sphincter tightens/closes - somatic
Rugae flatten - capacity increases - sympathetic
Intravesical pressure hardly changes - sympathetic
What results from bilateral lesions in the PSC?
Inability to store urine Reudction in capacity Excessive detrusor muscle activity Relaxation of urethra Premature voiding Leaky bladder
Where do afferent nerves originate in the urinary tract?
Bladder wall Thought to be stretch receptors but unknown Travel principally with para Some limited routing with sympathetic Pain sensation well localised
What are the signals the bladder needs to be void?
Paina and sensation from irritation of bladder
Temperature sensation
What mediates voiding of the bladder?
Independent neural apparatus
What is the flow rate of urine?
20-25 ml/s in men 24s
25-30 ml/s in women 22s
What is the threshold for feelings suggestive of a full bladder?
approx 400ml
What is the neural apparatus prescribing voiding of the bladder known as?
Voiding circuits. Controlled by micturition centres of the spinal cord. Mediated exclusively by parasympathetic neurones of the sacral division of the spinal cord
What do voiding circuits do?
Stong contraction of detrusor mucle
Increase in intravesical pressure
Relaxation of the internal urethral spincter
Voluntary relaxation of the external urethral sphincter
Expulsion of urine
Where do voiding circuits arise from?
Cerebral cortex -> The pons -> sacral levels of parasympathetc outflow -> detrusor muscle contracts -> external sphincter relaxes
What roots are involved in the mechanism of urinary voiding?
Cerebral cortex - somatic S2-4 (ventral horn) relaxes/opens ex urethral spincter
Parasympathetic division of ANS - S2-4 (lateral horns) increase detrusor activity
Why do sensation and voiding of the bladder not need to be under conscious control?
No sensory representation of the bladder in the sensory cotex
No motor representation of the bladder in the motor cortex
Nerve supply to the bladder is all by the ANS
What nerve supplies the external urethral sphincter?
Perineal branch of the pudenal nerve S2-4
Constricts urethra for maintenance of continence
Relaxation promotes voiding
What wil lower motor neurone lesion of S2,3,4 cause?
Reduced periana lsensation. Lax anal tone. Low detrusor pressure
Large residual urine +/- overflow incontinence
What do upper motor neurone lesions of S2,3,4 cause?
Dilated ureters
Thickened detrusor
High pressure detrusor contractions
Poor coordination with sphincters - DETRUSOR SPHINCTER DYSSYNERGIA
WHat are the symptoms of LUTS?
Frequency, urgency, nocturia, incontinence
Slow stream, splitting or straying, intermittency
Hesitancy, Straining, Terminal dribble
Post-micturition dribble, feeling of incomplete emptying
How is urinary incontinence defined?
The complaint of any involuntary leakage of urine
Name some types of UI.
Stress UI - on effort or exertion or on coughing or sneezing
Urge UI accompanied by or immediately proceeded by urgency
Mixed UI - both
Overflow incontinence