Pathology of Urinary Tract Infections Flashcards
How do UTIs present?
Dysuria
Altered frequency of urination
Smelly urine
In very young- unwell and failure to thrive
In very old- incontinence and off their feet
How does the bladder stop an influx of urine in health?
The ureter enters the bladder at an angle, and as the bladder fills it closes off the ureter
What parts of the urinary tract are sterile?
The whole tract apart from the terminal urethra
Why is a urinated specimen not sterile?
It is always contaminated by the terminal urethra flora
When should urine specimens for culture be taken and why?
After the initial urination as the initial urine is heavily contaminated, patient should stop midstream, discard urine and collect the next volume. This is known as a mid-stream specimen of urine (MSSU).
How do you tell contamination of urine samples from urinary infection?
An MSSU culture with 10^5 per ml is usually infection, 10^3-10^4 probable infection if symptomatic or 50% chance of infection if asymptomatic, <10^3 usually no infection.
What are the problems with urine culutres?
MSSU difficult to obtain in children and elderly
Some bacterial species not normally present in terminal urethra may be pathogenic at low colony numbers
What is the usual route of infection in UTIs?
Almost always ascending, infection in kidneys has usually spread from bladder etc
What inflammatory responses are triggered in each part of the urinary tract?
Urethra- urethritis
Bladder- cystitis
Ureter- ureteritis
Kidnet- acute pylonephritis (chronic pylonephritis if prolonged/recurrent infection)
What are the predisposing factors for a UTI?
Stasis of urine (obstruction, spinal cord/brain injury causing loss of full feeling in bladder)
Pushing bacteria up urethra from below (sexual activity in females, catheterisation)
Generalised predisposition to infection
What are the possible acute complications of UTIs?
Severe sepsis and septic shock
What are the possible chronic complications of UTIs?
Chronic damage to kidneys if repeat infections can cause hypertension or chronic renal failure
Calculi can cause obstruction and hydronephrosis, which can also cause hypertension and chronic renal failure
What are the consequences of obstruction of the urinary tract?
Proximal dilatation
Slowed urine flow means that they can’t flush bacteria out so can cause infection
Slowed urine flow causes sediment formation, which can lead to calculus (stone) formation and can cause further obstruction
What are the most common causes of obstructions causing UTIs in adults?
Males- Benign prostatic hyperplasia
Females- Uterine prolapse
Also tumours and calculi
What factors predispose females to UTIs?
Short urethra No prostatic bacteriostatic secretion Closeness of urethral orifice to rectum Sexual activity Pregnancy (pressure on ureters and bladder)
