11/14/24, 10\:38 AM Urinary Tract Infection (UTI)

Urinary Tract Infection (UTI)

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Key points ⚡
Succinct notes to superpower your revision
Urinary tract infection (UTI)\: in
commonly bacteria.
Incidence\: a
Cystitis\: lower UTI or bladder infection, often uncomplicated but can progress to upper or complicated UTI.
Pyelonephritis\: upper or complicated UTI, kidney infection usually due to bacterial ascent.
Recurrent bacterial cystitis\: two or more UTIs in six months or three or more in 12 months.
Microbiology\: common pathogens include uropathogenic E . c o l i , K l e b s i e l l a p n e u m o n i a e , and E n t e r o c o c c u s f a e c a l i s .
Risk factors\:
Females\: sexual activity, pregnancy, incontinence, post-menopause, cystocele, positive family history.
Males\: benign prostatic hypertrophy, urethral strictures.
Both sexes\: previous UTI, presence of a foreign body (e.g., catheter, stone), diabetes mellitus.
Children\: uncircumcision, vesicoureteral re
Symptoms\:
Lower UTIs\: dysuria, urgency, frequency, hesitancy, suprapubic pain, new-onset nocturia, urinary incontinence, haematuria.
Upper UTIs\:
Recurrent UTIs\: recurrent dysuria, urgency, frequency, suprapubic pain, cloudy urine, pelvic pain.
Neonates/Infants\: irritability, poor feeding, fever (>39°C).
Examination
Abdominal examination\: suprapubic tenderness, costovertebral tenderness (if kidney involvement).
Di
sexually transmitted infections, renal infarction.
Investigations\:
Bedside\: basic observations (vital signs), urinalysis (nitrites, leukocyte esterases, protein, haematuria), urine pregnancy test.
Laboratory\: urine microscopy, culture and sensitivity (MC&S).
Diagnosis\: based on clinical history and urinalysis, con
bacteriuria, pyuria).
Management\:
Conservative\: increased hydration, personal hygiene, vitamin C, D-mannose, cranberry products.
Medical\:
Lower UTI (cystitis)\: nitrofurantoin, trimethoprim (3-7 days); avoid trimethoprim in pregnancy.
Upper UTI (pyelonephritis)\: cefalexin, co-amoxiclav; IV antibiotics if severe.
Recurrent UTI\: prophylactic antibiotics (cephalexin, nitrofurantoin, trimethoprim), urinary antiseptic (methenamine
hippurate), vaginal oestrogen (post-menopausal patients).
Complications\: persistent lower urinary tract symptoms, staghorn calculi, pyelonephritis, emphysematous pyelonephritis
and cystitis, incontinence, renal abscess, prostatic abscess, chronic prostatitis, hypertension, renal failure.
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Introduction

A urinary tract infection (UTI) is an in
urethra) in response to pathogenic microorganisms, most commonly bacteria.
As one of the most common infections, UTIs a
young, sexually active women aged 18 to 24.
1

Aetiology

Cystitis, also referred to as a lower UTI, is a bladder infection. This is also categorised as an uncomplicated UTI, though it
can progress to an upper or complicated UTI.
Pyelonephritis, also referred to as upper or complicated UTI, is an infection of the kidney that often occurs via bacterial
ascent.
Recurrent bacterial cystitis is de

Microbiology

Urinary tract infections (UTIs) are caused by a wide range of pathogens, including Gram-negative and Gram-positive
bacteria, as well as fungi.
The causative organism may vary depending on whether the UTI is community-acquired or healthcare-acquired, and prior
exposure of the patient to antimicrobials.
2
The most common causative agent is uropathogenic E s c h e r i c h i a c o l i , followed by K l e b s i e l l a p n e u m o n i a e , and
E n t e r o c o c c u s f a e c a l i s .
3

Risk factors

Risk factors vary slightly depending on sex, which is an independent risk factor.
Females are 30 times more likely than males to develop a UTI due to the shorter urethra. As a result, there is a greater
probability of bacteria reaching the bladder before being expelled in urine, as the space between the opening of the
urethra and the bladder is shorter.
4
For females, risk factors to consider include\:
5
Sexual activity
Pregnancy
Incontinence
Post-menopause\: absence of oestrogen (consistent with vaginal atrophy, also known as genitourinary syndrome of
menopause)
Presence of a cystocele
Positive family history of UTIs
For males, risk factors to consider include\:
6
Benign prostatic hypertrophy
Urethral strictures
In both sexes, the following are risk factors\:
3,5,6
Previous history of UTI
Presence of a foreign body\: any indwelling catheter or foreign body (e.g. stone, suture, surgical material, or exposed
polypropylene mesh from pelvic surgery) signi
Diabetes mellitus
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In children, risk factors to consider are uncircumcision and vesicoureteral re
25% of children with
7

Clinical features

History

Typical symptoms of lower and uncomplicated UTIs (cystitis) include\:
8
Dysuria\: feeling of pain, discomfort or burning sensation while urinating
Urgency\: an unstoppable urge to urinate due to sudden involuntary contraction of the bladder muscles
Frequency\: urinating too often and at frequent intervals
Hesitancy\: inability to start the urine stream
Suprapubic pain
New-onset nocturia\: waking during the night to urinate
New-onset urinary incontinence\: loss of bladder control
Haematuria\: blood in the urine
Irritability, poor feeding, and fever (>39°C) are non-speci
Symptoms more indicative of upper and complicated UTIs (pyelonephritis) include\:
Flank pain
Fever and chills
Nausea and vomiting
Typical symptoms of recurrent UTIs (cystitis) include\:
Recurrent dysuria, urgency and frequency
Suprapubic pain
Cloudy urine
Pelvic pain
Other important areas to cover in the history include\:
Hydration and diet history
Prior history of UTIs
Sexual history (e.g. assess for risk of sexually transmitted infections)
Medication history (e.g. recent antibiotic history, immunosuppressive drugs)
For more information, see the Geeky Medics guide to urological history taking.

Clinical examination

In the context of a suspected UTI, a thorough abdominal examination is required.
Typical clinical
Suprapubic tenderness
Costovertebral tenderness, if kidney involvement (pyelonephritis)

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Di
1
Pyelonephritis
Renal stone
Vaginitis
Pelvic in
Acute prostatitis (men)
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Sexually transmitted infections
Renal infarction

Investigations

Bedside investigations

Relevant bedside investigations include\:
Basic observations (vital signs)\: to assess for systemic features (e.g. fever/tachycardia) which may suggest
pyelonephritis
Urinalysis\: to assess for the presence of nitrites, leukocyte esterases, protein, and haematuria.
Urine pregnancy test (hCG urine dipstick)\: to rule pregnancy in or out. This investigation is relevant, as UTIs are
common in pregnant women, and pregnancy will in

Laboratory investigations

Relevant laboratory investigations include\:
Urine microscopy, culture and sensitivity (MC&S)\: enables visualisation and quanti
blood cells, and bacteria or yeast if present. If bacteria are present, culture and sensitivity testing allows for guidance on
antibiotic sensitivity.
Always send MC&S in cases of complicated or recurrent UTI.

Diagnosis

The diagnosis of a UTI is made from the clinical history (symptoms) and urinalysis and can be further con
culture (with quanti
The following urinalysis\:
Nitrites\: strongly suggestive of bacteriuria, as nitrates are broken down into nitrites only in the presence of bacteria.
Leukocyte esterases\: an enzyme leukocytes produce in response to bacteria in the urine.
On MC&S, the following
Bacteriuria\: the presence of bacteria in urine. Historically, ≥ 10 5
bacterial colonies/mL of urine were needed to diagnose
a UTI. However, a UTI can be diagnosed if the symptoms are present with as low as 10 2
bacterial colonies/mL. If there is
bacteriuria without symptoms, this is termed asymptomatic bacteriuria. It is more common in older patients, and
asymptomatic bacteriuria is only treated in pregnant women, before urological operations or if there are associated
symptoms.
Pyuria\: the presence of WBCs in the urine. Sterile pyuria (WBCs in the urine, without infection) can indicate a range of
diagnoses, including renal malignancy, pelvic malignancy and genitourinary tuberculosis.

Management

Conservative management

Most UTIs will spontaneously resolve in about 20% of females, especially with increased hydration.
Lifestyle changes which may be bene
front to back for females), using vitamin C as a urinary acidi

Medical management

Lower UTI (cystitis)
Simple analgesia (paracetamol and ibuprofen) can be used for pain relief.
Three- or seven-day regimens of nitrofurantoin and trimethoprim are the recommended oral antibiotics as
therapy for lower/uncomplicated UTI in men, non-pregnant women, and children.
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NICE guidelines recommend checking any previous urine cultures, susceptibility results and antibiotic prescribing before
choosing an antibiotic.
In pregnant women, trimethoprim is contraindicated.
In individuals with an eGFR ≥ 45 ml/minute, nitrofurantoin is preferred, as it is renally excreted.
9
Upper UTI (pyelonephritis)
Simple analgesia (paracetamol and ibuprofen) with or without a weak opioid (e.g. codeine) can be used for pain relief.
Cefalexin and co-amoxiclav are the recommended oral antibiotics as
in men, non-pregnant women, and children.
NICE guidelines recommend checking any previous urine cultures, susceptibility results and antibiotic prescribing before
choosing an antibiotic.
If oral antibiotics are not tolerated or the patient is severely unwell, intravenous antibiotics should be used.
In pregnant women, cefalexin is the
10
UTIs in children
Babies under three months with a suspected UTI should be urgently referred to paediatrics for intravenous
antibiotics.
Children and babies may require imaging to assess for structural abnormalities (e.g. vesicoureteric re
renal scarring. Imaging options include ultrasound, micturating cystourethrography (MCUG) and dimercaptosuccinic
acid (DMSA) scanning.
The imaging modality depends on the child's age and the clinical presentation. Further details can be found in the
NICE guidelines.

Recurrent UTI

with recurrent UTIs.
Prophylactic oral antibiotics (cephalexin, nitrofurantoin and trimethoprim) are
These are to be taken daily or postcoitally, usually for 6 to 12 months, though this can be extended. A urinary antiseptic
can be added, such as methenamine hippurate.
In post-menopausal patients, vaginal oestrogen should also be considered.
11,12

Complications

If urinary tract infections continue untreated, complications which may occur include\:
3
Persistent lower urinary tract symptoms
Staghorn urinary calculi
Pyelonephritis
Emphysematous pyelonephritis and cystitis
Incontinence
Renal abscess
Prostatic abscess
Chronic prostatitis
Hypertension
Renal failure
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References

Stamm WE, Norrby SR. U r i n a r y t r a c t i n f e c t i o n s \: d i s e a s e p a n o r a m a a n d c h a l l e n g e s . Published in 2001. Available from\: [LINK].
Li R, Leslie SW. C y s t i t i s . StatPearls. Published 2022. Available from\: [LINK].
Bono MJ, Leslie SW, Reygaert WC. U r i n a r y T r a c t I n f e c t i o n . StatPearls. Published in 2022. Available from\: [LINK].
Foxman B. E p i d e m i o l o g y o f u r i n a r y t r a c t i n f e c t i o n s \: i n c i d e n c e , m o r b i d i t y , a n d e c o n o m i c c o s t s . Published in 2002. Available
from\: [LINK].
BMJ Best Practice. U r i n a r y t r a c t i n f e c t i o n s i n w o m e n . Published in 2021. Available from\: [LINK].
BMJ Best Practice. U r i n a r y t r a c t i n f e c t i o n s i n m e n . Published in 2021. Available from\: [LINK].
BMJ Best Practice. U r i n a r y t r a c t i n f e c t i o n s i n c h i l d r e n . Published in 2021. Available from\: [LINK].
Kaur R, Kaur R. S y m p t o m s , r i s k f a c t o r s , d i a g n o s i s a n d t r e a t m e n t o f u r i n a r y t r a c t i n f e c t i o n s . 2021. Available from\: [LINK].
Postgrad Med J. Published in
NICE. U r i n a r y t r a c t i n f e c t i o n ( l o w e r ) \: a n t i m i c r o b i a l p r e s c r i b i n g. Published in 2018. Available from\: [LINK].
NICE. P y e l o n e p h r i t i s ( a c u t e ) \: a n t i m i c r o b i a l p r e s c r i b i n g . Published in 2018. Available from\: [LINK].
NICE. U r i n a r y t r a c t i n f e c t i o n ( r e c u r r e n t ) \: a n t i m i c r o b i a l p r e s c r i b i n g. Published in 2018. Available from\: [LINK].
Anger J, Lee U, Ackerman AL, et al. R e c u r r e n t U n c o m p l i c a t e d U r i n a r y T r a c t I n f e c t i o n s i n W o m e n \: A U A / C U A / S U F U
G u i d e l i n e . Published in 2019. Available from\: [LINK].

Reviewer

Mr Derek Hennessy
Consultant Urologist
Mercy University Hospital, Cork, Ireland

Related notes

Acute Kidney Injury (AKI)
Chronic Kidney Disease (CKD)
Glomerular Disease (Glomerulonephropathies)
Haemodialysis
Henoch-Schönlein Purpura (IgA Vasculitis)

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Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
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