UROLOGY - UTI

Question 1

What are common organisms causing UTI?

Answer 1

E.coli 70%
Klebsiella pneumoniae
Proteus mirabilis
Enterococcus faecalis
Staphylococcus saprophyticus.

Question 2

What are the possible mechanisms for UTI?

Answer 2

Mostly caused by bacteria from a patient’s own bowel flora and ascends up the urethra
Rarely the infection may arise from bloodstream, lymphatics or by direct extension e.g. vesicocolic fistula

Question 3

What virulence factors does E.coli have which makes it a common pathogen for UTI?

Answer 3

Fimbriae - attach organism to perineurm and urothelium
Flagella
Aerobactin (to acquire iron)
Haemolysin (to form pores)
K capsule - allows bacteria to avoid phagocytosis and inactivation by the complement

Question 4

What are the innate host defences to prevent UTI?

Answer 4

Neutrophils
Urine osmolality and low or high pH
Complement activation with mucosal IgA
Commensalism organisms
Urine flow
Uroepithelium having tamm-horsfall proteins which have antibacterial properties

Question 5

What are risk factors for UTI?

Answer 5

Increased bacterial inoculation - sexual activity, urinary incontinence, faecal incontinence, constipation
Increased binding of uropathogenic bacteria - spermicide use, decreased oestrogen e.g. menopause
Decreased urine flow - dehydration or obstruction
Increased bacterial growth - DM, immunosuppression, obstruction, stones, catheter, urinary tract malformation, pregnancy

Question 6

What are the most typical clinical features of a lower uti?

Answer 6

Frequency of micturition day and night
Dysuria
Suprapubic pain and tenderness
Haematuria
Smelly urine
Fever
Distended bladder or enlarged prostate
Confusion, fatigue, incontinence in elderly
Febrile, sick, fussy with FTT in children

Question 7

How are UTIs diagnosed?

Answer 7

Examination - vital signs, palpate for flank or suprapubic tenderness and for pelvic/abdominal masses, check for blockage if urinary catheter in situ
Urine dipstick if under 65 and not pregnant - nitrites, leukocytes, RBC
Urine culture
FBC, U&Es, CRP and blood culture if systemically unwell
Imaging e.g. USS, cystoscopy or renal ultrasound in children to check kidney malformation

Question 8

What is a relapse of UTI?

Answer 8

Recurrence of bacteriuria with the same organism within 7 days of completion of antibacterial treatment

Question 9

What is re-infection of UTI?

Answer 9

When bacteriuria is absent after treatment for at least 14 days followed by a recurrence of infection with same/different organism.
This is not failure to eradicate but re-invasion of a susceptible tract

Question 10

What’s the natural history of outcome for UTI?

Answer 10

In patients with normal urinary tract, outcomes are very good
In those with abnormal urinary tracts, recurrence is more common and outcomes are less good
Recurrent UTI can cause renal scarring
Dissemination of infection can cause septicaemia (urosepsis)
Can ascend to cause pyelonephritis

Question 11

Whats the difference between complicated and uncomplicated UTI?

Answer 11

Uncomplicated is normal renal tract structure and function
Complicated involves a structural or functional abnormality of the genitourinary tract e.g. stones, catheters, obstruction

Question 12

What are symptoms of pyelonephritis?

Answer 12

Fever, rigor, vomiting, loin pain, cystitis symptoms, septic shock

Question 13

What is reflux nephropathy?

Answer 13

Chronic pyelonephritis
A combination of vesicoureteric reflex and infections acquired in early childhood
An incompetent vesicoureteric valve so urine reflux up ureter and incomplete bladder emptying
Predisposes to infection and causes kidney damage (papillary damage, tubulointerstitial nephritis and cortical scarring)
Reflux ceases around puberty with growth of bladder base

Question 14

What does chronic reflux nephropathy predispose you to in later life?

Answer 14

Hypertension
ESKD

Question 15

How do you manage a single, isolated attack of UTI?

Answer 15

Antibiotics - trimethoprim-sulfamethoxazole or nitrofurantoin 5-7 days
High fluid intake >2L daily

Question 16

How should you treat a UTI in men if symptoms suggest prostatitis?

Answer 16

A longer course of 4 weeks of fluoroquinolone

Question 17

Whats the moa of nitrofurantoin?

Answer 17

converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein

Question 18

Whats the moa of trimethoprim-sulfamethoxazole?

Answer 18

Sulfamethoxazole inhibits the synthesis of dihydrofolic acid. Trimethoprim inhibits thymidine and DNA synthesis. These two agents act synergistically in inhibiting folic acid synthesis.

Question 19

How do antibiotic choices for UTI change in pregnancy?

Answer 19

Can’t give trimethoprim/sulfamethoxazole in first trimester pregnancy as they inhibit folic acid synthesis
Can’t give nitrofurantoin in 3rd trimester of pregnancy as it may cause haemolytic anaemia of the newborn

Question 20

How can you prevent UTIs?

Answer 20

Drink plenty of water
Wipe front to back
Wash before sex and urinate after
Don’t use irritating feminine products/bubble baths
Don’t use a diaphragm, spermicide
Cranberry juice - substance in cranberries, called proanthocyanidins, might help prevent UTI-causing bacteria from sticking to the walls of the bladder and other urinary tract linings
Voiding at 2-3 hour intervals
Voiding before bed
Avoid constipation

Question 21

Infection by which organism is most common for UTI caused by prolonged bladder catheterisation?

Answer 21

These infections are often caused by Escherichia coli and Proteus mirabilis and candida spp

Question 22

Why do urine dipsticks become unreliable over 65?

Answer 22

Up to half of older adults and most with a urinary catheter, urine will have bacteria present without an infection

Question 23

What will 50% of women with suspected UTI but negative culture have?

Answer 23

Urethral syndrome - irritated urethra (urinary frequency, dysuria and suprapubic discomfort)

Question 24

How do you treat pyelonephritis in non-r pregnant women and men over 16?

Answer 24

If oral…
Co-amoxiclav 3x day for 7 days
Or ciprofloxacin, levofloxacin

If sepsis concerned then give IV

Question 25

How do you treat pregnant women with pyelonephritis?

Answer 25

Cefalexin twice a day for 7 days
IV cefuroxime if needed

Question 26

What are the 2 most common cause of UTIs in sexually active young women?

Answer 26

E.coli

Staphylococcus saprophyticus

Question 27

Outline the pathology of UTI?

Answer 27

Contamination
Colonisation in urethra and bladder
Inflammatory response and neutrophil infiltration
Bacteria multiple and evade the immune system because of virulence factors
Biofilms form
Bacteria can ascend towards the kidneys and cause an upper UTI
It can then enter the circulation through renal vein and cause sepsis

Question 28

Why do catheters put you at such high risk for UTI?

Answer 28

Because you bypass all the host defences and enter straight into the bladder

Question 29

Why does pregnancy put you at such high risk for UTI?

Answer 29

Urine has more glucose and protein in it
Growing uterus puts added pressure on the bladder
High progesterone levels cause smooth muscle relaxation leading to dilation and urinary stasis

Question 30

What are the consequences of uti in pregnancy?

Answer 30

Untreated UTI will lead to pre-term premature rupture of membrane, maternal chorioamnionitis, intrauterine growth retardation and low birth weight baby