Urinary Tract Infections Flashcards
What is the presentation of UTI?
Dysuria (pain on micturition)
Frequency
Smelly urine
Very young - failure to thrive
Very old - incontinnce, off their feet
What percentage of cardiac output is renal blood flow?
20 - 25%
How does urine change with oral intake of fluids?
Resorption of fluid is diminished if increase fluid intake therefore increased urine output
How do ureters function?
They have continuous trickle of urine - they do not store urine
How do the ureters interact with the bladder wall?
Ureters enter the bladder at an angle
Increasing pressure from the bladder as it fills closes off the ureter and stops the reflux of urine
What is the content of normal urine?
•Low pH, high osmolality, and high ammonia (NH3) content of normal urine
What is a useful property of prostatic secretions?
They are bacteriostatic
What portions of the normal renal tract are sterile?
All except the terminal urethra
Suprapubic aspirate of urine is sterile
What part of the stream do we use for urine specimen?
Mid stream
Initial voiding will flush out many terminal urethral floral bacteria
Mid stream specimen - urethral flora is diminished but always present - will always grow on culture - never a negative result
•MSSU – how to tell contamination from real infection?
Send to microbiology for culture under set conditions - bacterial multiply in log phase growth
105 is usually an infection - unless contamination (chances of which are less than 1 in 100)
Contamination more likely if they are asymptomatic
What values are associated with infection ‘sometimes’?
103 or 104
Probably an infection if there is symptoms
50% chance if there is no symptoms
When is there usually no infection?
When the culture shows less than 103
What is a problem associated with MSSU culture interpretation?
•Some bacterial species are not normally present in terminal urethra/rectal flora and may be pathogenic at low colony numbers
What are the micro-organisms that cause UTI?
- Bacteria mostly = gut flora, especially E.coli
- Viral infection rare
What is the route of infection in UTI?
Almost always ascending
If kidneys are infected this is usually because infection in the kidneys has usually spread up from the bladder infection
Upper UTI’s are more serious
What is the neame given to inflammation of the urethra, bladder ureter and the kidney?
- Urethra – urethritis
- Bladder – cystitis
- Ureter – ureteritis
- Kidney – acute pyelonephritis / chronic pyelonephritis
What are the predisposing factors to UTI?
Stasis of urine
Pushing bacteria up the urethra from below
Generalised predisposition
What are the causes of stasis of urine?
Obstruction
Loss of feeling of a full bladder - spinal cord / brain injury
What are the causes of pushing bacteria up from the urethra below?
Sexual activity
Catheterisation (and other urological procedures)
What is a generalised predisposition to infection?
Diabetes
Why does stasis of urine cause UTI?
•Bacteria that do get higher up do not get flushed out
What happens when there is obstruction at the level of the urethra?
Upper urethral and bladder dilation
Bilateral hydroureter
Bilateral hydronephrosis - chronic renal failure
What happens when there is obstruction of the renal pelvis on one side only?
Causes unilateral hydroureter and unilateral hydronephrosis
What are consequences of obstruction?
Proximal dilateion
Slowed urine flow - cannot flush out bacterial - infection
Slowed urine flow - sediments form - calculous (stone) formation - obstruction
Calculous - more dilation, increased calculous formation, more infections
What is a common cause of obstruction in children?
Vesicoureteric reflux - decreased angulation at angle into the bladder
What are common causes of obstruction in adults?
•Men – Benign Prostatic Hyperplasia (not a tumour) of prostate – functional and anatomical obstruction
Women - uterine prolapse
Both sexes - tumours and calculi
How does spinal cord/brain injury predispose to UTI?
•Decreased sensation therefore no sense of when to micturate and do not know to empty bladder completely - leave urine in bladder (high residual volume) - stasis of urine
How does sexual activity in females predispose to UTI?
Tends to move lower urethral flora up the tract (back wall of urethra is just in front of the vagina)
What are the predisposing factors that increase chances of getting a UTI in female sexual activity?
- 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
What is the effect of catheterisation on the urethral flora?
•Any instrumentation of urinary tract tends to move lower urethral flora up the tract
What parts of diabetes cause you to be more predisposed to infection?
Glucose in urine
Poor function of WBC
Summary of when people get UTI’s
What is an acute complication of UTI?
Severe sepsis and septic shock
What are chronic complications of UTI?
- Chronic damage to kidneys if repeated infections (chronic pyelonephritis) therefore hypertension, chronic renal failure
- Calculi - obstruction- Hydronephrosis - hypertension, chronic renal failure
