Urinary Tract Infections Flashcards
1
Q
How is the urinary tract protected from infection?
A
A variety of defence mechanisms
2
Q
What is the most important defence mechanism in protection of the urinary tract?
A
Regular flushing during voiding
3
Q
What does flushing during voiding do?
A
Removes organisms from the distal urethra
4
Q
What happens between voiding?
A
Organisms may ascend the urethra
5
Q
What is the result of organisms ascending the urethra between voiding?
A
Infection is commoner in females, because the urethra is comparitavely short
6
Q
What are the host factors in the pathogenesis of urinary disease?
A
- Shorter urethra
- Obstruction
- Neurological
- Ureteric reflux
7
Q
What may a shorter urethra lead to?
A
More infections in females
8
Q
What may cause urethral obstructions?
A
- Enlarged prostate
- Pregnancy
- Stones
- Tumours
9
Q
What can neurological urinary disease cause?
A
- Incomplete emptying
- Residual urine
10
Q
What can ureteric reflux cause?
A
Ascending infection from bladder, especially in children
11
Q
What are the bacterial factors in the pathogenesis of urinary disease?
A
- Faecal flora
- Adhesion
- K Antigens
- Haemolysins
- Urease
12
Q
What are faecal flora?
A
Potential urinary pathogens that colonise the periurethral area
13
Q
What is required for bacterial adhesion?
A
Fimbriae and adhesins
14
Q
What do fimbriae and adhesins allow in urinary infections?
A
Attachment to the urethral and bladder epithelium
15
Q
What do K antigens do?
A
Allow some E. coli to resist host defences by producing polysaccharide capsule
16
Q
What do haemolysins do?
A
Damage membranes and cause renal damage
17
Q
What produces urease?
A
Some bacteria, e.g. proteus
18
Q
What does urease do?
A
Breaks down urea for energy
19
Q
How severe are most UTIs?
A
Most are mild
20
Q
What may renal infections lead to?
A
Long term renal damage
21
Q
What is the urinary tract a common source of?
A
Life threatening Gram -ve bacteraemia
22
Q
What is the most common UTI?
A
Cystitis
23
Q
Where does cystitis affect?
A
The lower tract
24
Q
What may an upper UTI result from?
A
Haematogenous or ascending routes of infection
25
What are the types of lower UTI?
* Bacterial cystitis
* Abacterial cystitis
* Prostatitis
26
What does bacterial cystitis cause?
Frequency and dysuria, often with pyuria and haematuria
27
What does abacterial cystitis cause?
The same as bacterial, but without significant bacteriruia
28
What does prostatitis cause?
* Fever
* Dysuria
* Increased frequency
* Perineal and low back pain
29
What are the types of upper UTIs?
* Acute pyelonephritis
* Chronic interstitial nephritis
30
What does acute pyelonephritis cause?
The symptoms of cystitis plus fever and loin pain
31
What does chronic interstitial nephritis cause?
Renal impairment following chronic inflammation
32
What can cause asymptomatic UTIs?
Covert bacteriuria
33
How can covert bacteria causing UTIs be detected?
Only in culture
34
When is covert bacteria causing UTIs important?
In children and pregnancy
35
What are the most common pathogens in the community?
Gram -ve rods, *particularly the enterobacteriaceae*
36
What % of bacteria in the community are gram -ve rods?
80%
37
What are enterobactericeae known as?
Coliforms
38
What type of coliform is particularly common in the community?
E. Coli
39
Who may develop a UTI due to coagulase-negative staphylococci?
* Young women
* Hospitalised patients
40
Give an example of a coagulase-negative staphylococci
*Staph. Saprophyticus*
41
Why are young women and hospitalised patients at a higher risk of developing a UTI due to coagulase negative staphylococci?
Due to increased risk factors, *e.g. catherisation*
42
Why does cathertisation increase the risk of UTIs?
Biofilms
43
Who do uncomplicated UTIs develop in?
Healthy women
44
Who do complicated UTIs develop in?
* Pregnancy
* Treatment failure
* Suspected pyelonophritis
* Complications
* Males
* Paediatrics
45
Does urine need to be cultured in uncomplicated UTIs?
No
46
Why is there no need to culture urine in uncomplicated UTIs?
Infection is indicated by nitrite/leukocyte esterase dipstick testing
47
How can samples be collected in complicated UTIs?
* Mid-stream specimen
* Catheter samples
* Supra-pubic aspiration
* Adhesive bags
48
Why is a mid-stream sample collected when investigating complicated UTIs?
As we do not want to culture the urethras normal flora, so allow for a small amount of urine to be passed to 'clear' it before collecting the sample
49
When may an adhesive bag be used to collect a urine sample
In small children, *who it is difficult to get samples in*
50
What is the false positive rate of collecting a urine sample by placing an adhesive bag over genitals?
20%
51
Where is a catheter sample taken from?
*Not from the bag,* but by using a needle up a special tube in the catheter
52
What happens in supra-pubic aspiration?
A sample of bladder urine is obtained by using a needle through the abdominal wall
53
How commonly is supra-pubic aspiration used?
Rarely
54
Under what conditions do urine samples need to be transported?
* Kept at 4oC
* Small amount of boric acid in the collection tube
55
What is the purpose of the conditions that urine samples are kept under once collected?
It stops bacterial division to keep the sample representative of the collection time
56
What investigations are undertaken on urine samples?
* Turbidity
* Dipstick testing
57
What is meant by investigating turbidity?
Look to see if the sample is cloudy
58
What is cloudy urine indicative of?
A UTI
59
What is being looked for during dipstick testing?
* Leukocyte esterase
* Nitrite
* Haematuria
* Proteinuria
60
What does leukocyte esterase in urine indicate?
Presence of WBCs
61
What does nitrite indicate in urine?
The presence of Nitrate reducing bacteria
62
Can haematuria and proteinuria be used to diagnose a UTI?
No, *because there are many causes of these symptoms*
63
When is microscopy used to investigate UTIs?
* Kidney disease
* Suspected endocarditis
* Children under 6
* Schistosomiasis
* Suprapubic aspirates
* When requested
64
What may indiciate kidney disease in UTIs?
* Lion pain
* Nephritis
* Hypertension
* Toxaemia
* Renal colic
* Haematuria
* Renal TB
* Casts
65
What distinguishes between bacteriuria/contamination in a urine culture?
A number of colony forming units \> 100,000per ml (105 cfu/ml)
66
What % predictive is a single urine specimen?
80%
67
When is a urine culture used?
To investigate complicated UTIs
68
Why is a urine culture preferential to a urine sample?
Increased sensitivity *(down to 102 cfu/ml)*
69
What can a urine culture be used to determine?
* Epidemiology of isolates
* Sensitivity
* Specimen quality
70
How can a urine culture be used to control specimen quality?
Can differentiate between properly collected and contaminated samples
71
How can a urine culture be used to differentiate between properly collected and contaminated samples?
Poorly collected samples may contain epithelial cells
72
How is a urine culture report interpreted?
* Clinical details
* Quality of specimen
* Delays in culture
* Microscopy *(if available)*
* Organism(s) located
73
What clinical details should be considered when interpreting a culture report?
* Symptoms
* Previous antibiotics
74
What is sterile pyuria?
Pus in urine
75
What happens in sterile pyuria?
A UTI is present, but unable to be cultured
76
Why may sterile pyuria occur?
* The patient may have aleady been treated with antibiotics
* Infected with bacteria that are difficult to isolate or culture
* Tuberculosis
* Appendicitis
77
Give an example of a bacteria that is difficult to isolate or culture?
Chlamydia
78
Why may appendicitis cause sterile pyuria?
The appendix is stuck on the bladder
79
Do all adult women who present with classic UTI symptoms have a UTI?
No
80
How are adult women who present with classic UTI symptoms treated?
As though they have one, until proved otherwise
81
What may cause classic UTI symptoms that is not a UTI?
* Significant bacteriuria
* Urethral syndrome
82
What may cause urethral syndrome?
* Low-count bacteriuria
* Fastidious organisms
* Vaginal infection/inflammation
* Sexually transmitted pathogens
* Mechanical, physical, and chemical causes
83
What may sexually transmitted pathogens cause?
Urethritis
84
What are the general principles of UTI treatment?
* Increase fluid intake
* Address underlying disorder
85
What is done when bacteria are present asymptomatically in UTIs?
Only treat once symptoms appear
86
How is an uncomplicated UTI treated?
3 day course of antibiotics
87
Why is an uncomplicated UTI treated with a 3 day course of antibiotics?
3 days reduces the selection pressure for resistance
88
How is a complicated UTI treated?
7 day course of antibiotics
89
What antibiotic is **not** appropriate for treatment of a complicated UTI?
Amoxicillin
90
Why is amoxicillin not appropriate in the treatment of a complicated UTI?
50% of isolates are resistant
91
How is pyelonephritis/septicaemia treated?
14 day course of antibiotics
92
What is used in the treatment of pyelonephritis/septicaemia?
A more potent agent with systemic activity
93
When is prophylaxis used in the treatment of UTIs?
When there are 3 or more episodes in one year with no treatable underlying condition
94
What is given in UTI prophylaxis?
Single, low, nightly dose of antibiotics
95
What is the purpose of the antibiotics given in UTI prophylaxis?
To prevent bacteria build up in static urine
96
What must be done in UTI prophylaxis?
All breakthrough infections documented
97
What do diuretics do?
Block the reabsorption of Na+ and therefore water by the kidney
98
What are the types of diuretics?
* Loop
* Thiazide
* K+ Sparing
* Aldosterone Antagonists
99
What kind of diuretic is most powerful?
Loop
100
What are loop diuretics capable of?
Causing the excretion of 10-25% of filtered Na+ ions
101
How do loop diuretics work?
By blocking the Na-2Cl Symporter in the apical membrane
102
Give two examples of loop diuretics
* Furosemide
* Bumetanide
103
Draw a diagram illustrating the function of loop diuretics
104
Where do thiazide diuretics act?
On the early DCT
105
What are thiazide diuretics capable of?
Inhibiting only 5% of Na+ reabsorption, *less potent than loop diuretics*
106
Where are thiazide diuretics ineffective?
In the treatment of renal failure
107
How do thiazide diuretics work?
By blocking the Na-Cl Symporter
108
Give an example of a thiazide diuretic
Bendroflumethiazide
109
Draw a diagram illustrating the action of thiazide diuretics
110
Where do K+ sparing diuretics and aldosterone antagonists act?
On the late DCT
111
What do K+ sparing diuretics and aldosterone antagonists act to do?
Reduce Na+ channel activity
112
What are K+ sparing diuretics and aldosterone antagonists capable of doing?
*Both mild diuretics,* inhibiting only 2% of Na+ reabsorption
113
What effect do K+ sparing diuretics and aldosterone antagonists have on K+?
They reduce the loss of K+
114
What is a potential problem with K+ sparing diuretics and aldosterone antagonists?
They can both produce life threatening hyperkalaemia
115
When may K+ sparing diuretics and aldosterone antagonist cause life threatening hyperkalaemia?
In renal failure
116
Give an example of a K+ sparing diuretic
Amiloride
117
Give an example of an aldosterone antagonist
Spironolactone
118
Draw a diagram illustrating the action of K+ sparing diuretics and aldosterone antagonists
119
What are the potential adverse effects of diuretic use and abuse?
* Effects on potassium
* Hypovolaemia
* Hyponatraemia
* Increase uric acid levels in the blood
* Metabolic effects
* Carbonic anhydrase inhibition
120
What kind of diaretics may cause hypokalaemia?
Loop and thiazide
121
Why may loop and thiazide diuretics cause hyperkalaemia?
Because they reduce the loss of potassium in urine
122
Is hypo or hyperkalaemia life threatening?
Either can be
123
What is the result of diuretics reducing ECF volume?
They cause the activation of RAAS
124
What is the effect of diuretics causing the activation of RAAS?
It will cause aldosterone secretion, increasing Na+ absorption and K+ secretion, helping contribute to hypokalaemia
125
Draw a diagram illustrating the potential adverse effects of diuretics
126
What is hypovolaemia?
Decreased ECF volume
127
What is hypovolaemia due to?
Excessive loss of Na+ and water
128
What should be monitered in the case of hypovolaemia?
* Weight
* Signs of dehydration
* BP
129
How can BP be monitered in hypovolaemia?
Look for postural hypertension
130
What can increased uric acid levels in the blood do?
Precipitate attack of Gout
131
What are the potential metabolic effects of diuretics?
* Glucose intolerance
* Increased LDL levels
132
What diuretics inhibit carbonic anhydrase?
Those that act in the PCT by inhibiting the enzyme carbonic anhydrase
133
What is the effect of carbonic anhydrase inhibition?
It interferes with Na+ and HCO3- reabsorption
134
Why are carbonic anhydrase inhibitors no longer used as a diuretic?
As HCO3- loss leads to metabolic acidosis
135
What are diuretics used to treat?
* Conditions with ECF expansion and oedema
* Acute pulmonary oedema
* Hypertension
136
What conditions have ECF expansion and oedema?
* Congestive heart failure
* Nephrotic syndrome
* Kidney failure
* Ascites and oedema due to cirrhosis of the liver
* Hypercalcaemia
* Cerebral oedema
* Glaucoma
137
What diuretic is used to treat kidney failure?
Loop
138
What diuretic is used to treat ascites and odema due to cirrhosis or the liver?
Spironolactone
139
What is used to treat acute pulmonary oedema?
IV Furosemide
140
What causes acute pulmonary oedema?
Left heart failure
141
How is is hypertension treated?
Thiazide diuretics or spironolactone
142
When is spironolactone used to treat hypertension?
In primary hyperaldosteronism *(Conn's syndrome)*
143
What diuretics are used to treat hypercalcaemia?
Loop
144
Why are loop diuretics used to treat hypercalcaemia?
They promote calcium excretion by the Loop of Henle
145
What diuretics are used in the treatment of cerebral oedema?
Osmotic diuretics
146
Give an example of an osmotic diuretic
Mannitol
147
What diuretic is used in the treatment of glaucoma?
Acetazolamide
148
What kind of diuretic is acetazolamide?
Carbonic anhydrase
149
What substances have diuretic action?
* Alcohol
* Coffee
* Other drugs
150
How does alcohol have a diuretic action?
It inhibits ADH release
151
How does coffee have a diuretic action?
It increases GFR and decreases tubular Na+ reabsorption
152
What drugs have a secondary diuretic action?
* Lithium
* Demeclocycline
153
How do lithium and democlocycline have a diuretic action?
They inhibit ADH action on collecting ducts
154
What is the symptom of diseases causing diuresis?
Polyuria
155
What is polyuria?
More than 2.5L urine/day
156
What diseases cause diuresis?
* Diabetes mellitus
* Diabetes insipidus (cranial)
* Diabetes insipidus (nephrogenic)
* Psychogenic polydipsia
157
How does diabetes mellitus cause diuresis?
Glucose in filtrate leads to osmotic diuresis
158
How does cranial diabetes insipidus cause diuresis?
Decreased ADH release from posterior pituitary leads to diuresis
159
How does nephrogenic diabetes insipidus cause diuresis?
Poor response of collecting ducts to ADH leading to diuresis
160
What is psychogenic polydipsia?
Increased intake of fluid
