Urinary Tract Infection (UTI) Flashcards by Andrew Hay

What is dysuria?

Pain on micturition

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How does a UTI present?

Dysuria
Frequency
Smelly urine

Very young: unwell, failure to thrive

Very old: incontinence, off their feet

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Why do the ureters enter the bladder at an angle?

Enter bottom of bladder at angle so that increasing pressure from bladder as it fills -> closes off ureter and stops reflux of urine

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What are the bacteriostatic properties of the normal urinary tract?

Free flow of urine through normal anatomy- assumes drinking enough fluids

Low pH, high osmolarity, and high ammonia (NH3) content of normal urine

Prostatic secretions are bacteriostatic

Anti-bacterial antibodies

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How much of the urinary tract is normally sterile?

All urinary tract except for terminal urethra

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How can you bypass the terminal urethra to take a clean sample of urine?

Suprapubic aspirate of urine

-Needle straight into bladder

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Why do we take a midstream sample (or suprapubic aspirate) for urine MC&S?

Urinated sample will always be contaminated by terminal urethral flora

Initial void will wash terminal urethra -> sample taken after will be more sterile avoiding false positives

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Explain how you carry out a mid stream sample

Patient voids and stops mid-stream, discarding urine, then collects next volume of urine = MSSU (midstream specimen of urine

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Can you ever get rid of all terminal urethral flora by a MSSU?

Urethral flora will be diminished by always present

Will always grow in culture so never a negative result

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What does MSSU stand for?

Mid Stream Specimen Urine

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How do you tell contamination from real infection in MSSU?

Microbiology for culture under set conditions

Bacteria multiply in log phase growth

10^5 per ml

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A MSSU culture result of 10^3 would indicate what?

10^3 and 10^4 need to be interperated clinically:

If symptomatic probably infection
If asymptomatic 50% infection

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In which populations is an MSSU difficult to collect?

Young children and elderly

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What are the problems with interpretation of urine culture?

Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers

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What micro-organisms cause UTI?

Bacteria mostly = gut flora, especially E. coli

Viral infection rare

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What is the route of infection in UTI?

Almost always ascending from terminal urethra

Infection in kidneys has usually spread up from bladder infection

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Which is more serious:

Upper UTI or Lower UTI?

Upper UTI more serious

What is urethritis?

INFECTION of urethra

Usually itis = inflammation but here almost always infection

What is cystitis?

Inflammation/infection of bladder

What is ureteritis?

Infection of the ureter

What is acute pyelonephritis?

Kidney infection/ inflammation

If recurrent/ prolongued infection -> chronic pyelonephritis

What are the predisposing factors for a UTI?

Stasis of urine
Pushing bacteria up urethra from below
generalised predisposition to infection

How can stasis of urine come about?

Obstruction, whether congenital (presents in childhood) or acquired (adults).
Loss of “feeling” of full bladder - spinal cord/ brain injury

How can pushing bacteria up urethra from below come about?

Sexual activity in females

Catheterisation (and other urological procedures)

What may cause a generalised predisposition to infection?

e.g. Diabetes

How does obstruction of the urethra effect the urinary tract?

Upper urethral and bladder dilatation If this continues -> bilateral hydroureter -> bilateral hydronephrosis -> chronic renal failure

What does unilateral hydroureter indicate as opposed to bilateral hydroureter?

Unilateral = obstruction above bladder Bilateral = obstruction below bladder

What are the consequences of obstruction?

Proximal dilatation Slowed urine flow -> cannot flush out bacteria -> infection Slowed urine flow -> sediments form -> calculous formation -> obstruction -> repeat cycle

What is the obstruction triad?

Infection -> calculi -> obstruction -> infection etc

What is obstruction in children usually caused by?

There are numerous renal tract abnormalities -Usually one of these Always investigate at first presentation and send to paediatric surgeons

What is the most important renal tract abnormality for obstruction in children?

Vesicoureteric reflux

What is vesicoureteric reflux?

Normally ureters insert into bladder at angle Decreased angulation in vesicoureteric reflux -> ureter isnt closed off by increasing bladder pressure -> reflux -> hydroureter -> hydronephritis

What are common causes of obstruction in adults?

Males - Benign Prostatic Hyperplasia (NOT a tumour) -> functional and anatomical obstruction Females - Uterine prolapse Both sexes - Tumours and calculi

What is the residual bladder volume?

Volume of fluid left in bladder after urination You want this to be as small as possible to prevent static urine

How does spinal cord/ brain injury predispose to UTI?

Decreased sensation -> no sense of when to micturate and do not know how to empty bladder completely -> leave urine in bladder -> high residual volume -> stasis of urine

How does female sexual activity tend to lead to UTI?

Move lower urethral flora up the tract (back wall of urethra is just in front of vagina)

Why are females more predisposed to UTI?

Short urethra Lack of prostatic bacteriostatic secretion Closeness of urethral orifice to rectum Sexual activity (helps if void after intercourse) Pregnancy - pressure on ureters and bladder

How does catheterisation predispose to UTI?

Any instrumentation of urinary tract tends to move lower urethral flora up the tract

How does diabetes predispose to UTI?

Glucose in urine Poor function of WBC

What are the acute complications of UTI?

Severe sepsis and septic shock

What are the chronic complications of UTI?

Chronic damage to kidneys if repeated infections (chronic pyelonephritis) -> hypertension, chronic renal failure Calculi -> obstruction -> hydronephrosis -> hypertension, chronic renal failure