7 - UTIs And Diuretics

Question 1

Who are UTIs most common in?

Answer 1

Women and the elderly.

Question 2

Why are UTIs more common in women?

Answer 2

They have a shorter urethra (infection is spread via faecal-perineal-urethral route).

Question 3

What are some of the causes of UTIs (that are not predetermined - i.e. for women)?

Answer 3

Obstruction - enlarged prostate, pregnancy, renal stones, tumours.

Neurological problems - incomplete emptying / residual urine (stagnation increases risk of infection).

Pelvicureteric reflex - ascending infection from bladder due to backflow of urine up the ureters (more common in children).

Question 4

What are some of the common sites and causes of UTIs?

Answer 4

Question 5

What are the major bacterial causes of UTIs?

Answer 5

Coliforms (E. Coli) - (potentially lead to sepsis?); Klebsiella spp., Proteus (produce urease). Enterococci (gram positive).

Question 6

What are some of the adaptations of bacteria that will help them to cause UTIs? (Hint: There are four).

Answer 6

Fimbriae - increases adherance to host epithelium. K antigen allows polysaccharide capsule production (helps avoid immune response). Urease (produced by proteus) breaks down urea forming a favourable environment for bacteria to grow in. Haemolysins damage host membranes and causes renal damage.

Question 7

How might UTIs manifest themselves?

Answer 7

Lower UTI - changes in frequency and dysuria.

Acute pyelonephritis (upper UTI)

Chronic nephritis

Asymptomatic bacteriuria (elderly women)

Septicaemia.

Question 8

When might asymptomatic bacteriuria be a problem in some women?

Answer 8

Pregnant - premature birth –> low birth weight May develop into pyelonephritis in women if it becomes symptomatic.

Question 9

What exactly is acute pyelonephritis?

Answer 9

Infection within the renal pelvis, which may or may not extend to the renal parenchyma. Usually caused by backflow of urine (females: pelviuteral reflux) into the ureters (although can be through haematogenous spread. Repeated bouts of acute pyelonephritis may progress to chronic pyelonephritis.

Question 10

How can we differ between lower UTIs and upper UTIs (acute pyelonephritis)?

Answer 10

Lower UTIs - dysuria, frequency, urgency - sometimes low grade fever. Upper UTIs (acute pyelonephritis) - fever, back/loin pain (often unilateral worse at the renal angle) - may have dysuria and frequency problems.

Question 11

What is the difference between uncomplicated and complicated UTIs?

Answer 11

Uncomplicated: in otherwise healthy women of child-bearing age (no need to culture urine). Complicated: pregnancy, recurrent infections, suspected pyelonephritis, male, paediatric, (must culture urine).

Question 12

What is MSU? What is it used for? How else may samples for this purpose be obtained?

Answer 12

Midstream urine (urinate a small volume; stop; start and collect - not necessary in children) - in order to send for urinalysis. Catheters can also be used (providing it is a fresh urine sample… or else stagnant… bacteria multiply… 20% false positive). Supra-pubic aspirations may be carried out (needle through abdominal, anterior wall).

Question 13

How must urine be transported to the lab?

Answer 13

Low temperatures (4 degrees) with boric acid (to stop bacteria multiplying).

Question 14

How is urine analysed?

Answer 14

Turbidity (visual inspection) Urine dipstick (nitrites, leukocyte esterase, haematuria, proteinuria).

Question 15

How sensitive and specific are nitrites (N) and leukocyte esterase (L)? N & Ls?

Answer 15

N: not very sensitive (16%) but very very specific (97%) L: very sensitive (89%) but moderately specific (78%) N & Ls: 89% sensitive; 97% specific. N.B. Sensitivity refers to: If it is present, how good is the test at detecting it; Specificity is: If the test finds something positive - how certain it is, definitely there.

Question 16

Who is dipstick testing useful in?

Answer 16

Children >3 years; Men with mild/non-specific symptoms; Elderly/institutionalised women.

Question 17

Who is dipstick testing not useful in?

Answer 17

Uncomplicated UTIs in women, men with typical/severe symptoms. Catheterised patients, older patients without features of infection (asymptomatic bacteriuria common).

Question 18

When would urine be cultured? What main advantage does it have over urine dipstic tests?

Answer 18

Investigations of males, children and other complicated UTIs - it gives more sensitive results.

Question 19

In adult women with symptomatic UTIs what can this be subdivided into?

Answer 19

Significant bacteriuria (50%) Urethral syndrome (50%)

Question 20

What falls under urethral syndrome?

Answer 20

Low-count bacteriuria, Fastidious organisms (organisms with complex nutritional requirements) Vaginal infection/inflammation, Urethritis (sexually-transmitted pathogens) Mechanical, physical and chemical causes.

Question 21

Is imaging of the urinary tract ever necessary with UTIs?

Answer 21

Yes. Indicated for all children. valuable in septic patients (identify renal involvement); males (newborns suspected of posterior urethral valve) females (suspected of vesicouteral reflux - backflow of urine from the bladder to the ureters).

Question 22

What is sterile pyuria? When might sterile pyuria be observed?

Answer 22

Sterile pyuria is the presence of elevated leukocytes in the urine despite appearing sterile using urine cultures. Antibiotics, Urethritis (chlamydia/gonococci), Vaginal infection/inflammation, (Urinary TB, Appendicitis - very rare causes)

Question 23

Asymptomatic bacteriuria is very common in elderly females. How do we manage these patients?

Answer 23

No urine dipstick - often have pyuria (raised leukocytes). No risk of increased morbidity. Action only necessary if suspected pregnancy or proceeding urology surgery (bacteria may invade).

Question 24

How do we treat UTIs?

Answer 24

Increase fluid intake and address underlying cause. 3 day course of antibiotics (trimethoprim - DHFR inhibitors - or nitrofurantoin - both inhibit DNA synthesis) for uncomplicated UTIs; 5 days for complicated UTIs (same, cephalexin also an option). If the patient is catheterised we only treat if systemically unwell.

Question 25

Why are antibiotics only given for 3 days to this with uncomplicated UTIs?

Answer 25

Reduces likelihood of bacteria developing antibiotic resistance.

Question 26

How do we treat pyelonephritis/septicaemia?

Answer 26

14 day course of antibiotics with systemic activity (and good gram negative coverage). Possibly IV initially. Co-amoxiclav and Ciprofloxacin are used.

Question 27

If someone has repeated episodes of UTIs, what can we do for them?

Answer 27

If there is no underlying cause and they have had >3 episodes in a year, we can give drug prophylaxis. This is done through a single nightly dose of trimethoprim/nitrofurantoin.