Pathology of Urinary Tract Infection Flashcards
What is the common presentation of a UTI?
Dysuria
Frequency
Smelly urine
Approximately what proportion of the cardiac output do the kidneys receive?
25%
Do the ureters store urine?
No, they have a continuous trickle of urine
How is influx of urine from the ureters into the bladder stopped?
The ureters enter the bladder at an angle. When the bladder fills and expands this angle is shut off by compression by the bladder wall and urine ceases to enter
Describe the pH, osmolarity and ammonia content of normal urine
Low pH
High osmolarity
High ammonia content
What parts, if any, of the urinary tract are sterile?
The entire tract bar the terminal urethra, which is contaminated with perineal and rectal flora
How can a sample of urine be taken in a completely sterile manner?
Suprapubic aspirate
Describe the challenges of obtaining a non-contaminated sample of urine
Because the terminal urethra is contaminated, any urine sample passed by the patient will contain bacteria. Because the healthy bladder is completely sterile, this makes determining whether the bacteria in the sample is from the bladder or from the terminal urethra
What is an MSSU?
A mid-stream specimen of urine, designed to avoid the initial flush of bacteria into the same from the first void of urine, but it will always be present
How is it determined whether the flora cultured from a urine sample indicated a UTI or normal terminal urethral flora?
They are calculated in log, and a culture of 10^5 usually indicates infection
Below 10^3 usually rules out infection
What are some causes of UTI?
Mostly bacteria - gut flora, especially e.coli
Viral infection rare
Describe the rout taken by UTIs
Almost always ascending up the tract, the higher the infection the more serious
What is the name for inflammation of the urethra?
Urethritis
What is the name for inflammation of the bladder?
Cystitis
What is the name for inflammation of the kidney (acute)?
Acute pyelonephritis
What is the name for inflammation of the kidney (chronic)?
Chronic pyelonephritis
What is urethritis?
Inflammation of the urethra
What is the name for inflammation of the ureter?
Ureteritis
Give three predisposing factors for UTIs
Stasis of urine
Pushing bacteria up urethra from below
Generalised predisposition to infection
What may cause stasis of urine?
Obstruction
Loss of bladder sensation
What may cause UTI as a result of pushing bacteria up the urethra from below?
Sexual activity in females
Catheterisation (and other urological procedures)
Describe the effects of an obstruction at the level of the urethra
There begins a dilation of the upper urethra and bladder, which leads to bilateral hydroureter
this progresses to bilateral hydronephrosis and chronic renal failure
What is the effect of an obstruction at the level of the renal pelvis one on side only?
Unilateral hydroureter develops and progresses to unilateral hydronephrosis
What make up the triad of consequences of obstruction?
Infection
Calculi
Obstruction
What is the most important cause of obstruction in children?
Vesicoureteric reflux
What is vesoureteric reflux?
Where there is decreased angulation of the point of entry of the ureter into the bladder wall. This means that the compression of the filling bladder does not fully compress the ureter and urine is allowed to reflex up the ureter
What is the most common cause of obstruction in male adults?
Benign Prostatic Hyperplasia - functional and anatomical obstruction - not a tumour
What is the most common cause of obstruction applying only to women?
Uterine prolapse
How does loss of sensation of the bladder cause stasis of urine?
Decreased sensation in the bladder due to spinal cord or brain injury mens that the ability to know when to empty the bladder is impaired and stasis of urine results
What factors inherent in women predispose them to UTIs?
A short urethra
Lack of prostatic bacteriostatic secretion
Closeness of urethral orifice to rectum
Sexual activity
Pregnancy - pressure on ureters and bladder
Give two factors relating to diabetes which predispose to UTI
Glucose in the urine
Poor function of WBC
What are acute complications of UTIs?
Severe sepsis
Septic shock
What are chronic complications of UTIs?
Chronic damage to the kidneys if repeated infections (chronic polynephritis) which leads to hypertension and chronic renal failure
Calculi, leading to obstruction, hydronephrosis, hypertension and chronic renal failure
