Overview #
- Definition: a lower urinary tract infection of the bladder (cystitis) or upper urinary tract infection of the kidneys (pyelonephritis)1
- Diagnosed based on symptoms and positive urine dipstick analysis or urine MCS
- Most common pathogen: E. Coli1
- Do NOT treat asymptomatic bacteriuria in non-pregnant women as it does not reduce mortality or morbidity
Triage #
Can be handed over if the patient is stable
Causes #
Uncomplicated UTIs2: [call-out box to classification definition]
- Escherichia coli (70 – 95%)
- Staphylococcus saprophyticus (5 – 10%)
Complicated UTIs2: [call-out box to classification definition]
- Escherichia coli (20-50%)
- Klebsiella
- Proteus
- Pseudomonas species
- Candida
Risk factors for women3: [call-out box]
- Poor hygiene practices
- Sexual intercourse
- Contraceptive diaphragms (especially with spermicides)
- Past history of childhood UTIs
- Prior antibiotic use
- Urinary incontinence
- Cystocoele and large postvoid residual volumes
- Atrophic vaginitis (post menopause)
Risk factors for men4: [call-out box]
- Benign prostatic hypertrophy
- Urinary tract stones
- Urological surgery, instrumentation, catheterisation
- Urethral strictures
Clinical Features #
History(3,4)
- Dysuria
- Increased frequency
- Nocturia
- Cloudy urine
- Malodourous urine
- Urgency
- Haematuria
- Risk factors as above
Examination
- Fevers, rigors (may not be present in older patients)
- Suprapubic pain/tenderness
- Flank pain or renal angle tenderness – more indicative of pyelonephritis [call out box with diagnostic criteria of pyelonephritis: fever, renal angle/flank pain/tenderness, systemic illness]
- Delirium (in older patients)
Diagnosis #
- Positive history/examination + positive urine investigation findings5
- Do NOT treat asymptomatic bacteriuria in non-pregnant women as it does not reduce mortality or morbidity
Investigations #
Initial investigations
Investigation | Significance |
Urine dipstick6 | NitritesLeukocytesRBCLikelihood of UTI++/–Likely++/-+Likely-+-Neutral (UTI as likely as other diagnosis)—Unlikely |
Urine MCS (MSU) | Useful to determine appropriate antibiotic therapy |
FBE | Elevated WCC suggests infection |
CRP | Elevated CRP represents inflammation (note delayed response) |
UEC/LFT | AKI secondary to infection/shockRenal and liver function will also influence antibiotic choice |
Further investigations
Investigation | Indication |
Post void residual | To investigate bladder function; Incomplete bladder emptying can predispose patients to UTIs |
Renal tract ultrasound | To investigate for urinary tract obstruction, kidney stones, hydronephrosis, renal scarring or other structural abnormalities that can predispose to UTIs |
CT-KUB | To investigate for urinary tract obstruction, kidney stones, hydronephrosis, renal scarring, pyelonephritis or other structural abnormalities that can predispose to UTIs |
Investigations to consider in children with recurrent UTIs7 [callout box]
- Renal ultrasound: looking for any anatomical abnormalities of the urinary tract: dilation of the renal pelvis or ureters, distention of thick-walled bladder, renal stones, ureterocele, bladder wall trabeculation, high post-void residual volume, enlarged rectal diameter; renal abscess
- Dimercaptosuccinic acid (DMSA) scan: looking for renal scarring post UTIs and diagnosing upper tract infections (pyelonephritis)
- Voiding cystourethrogram: looking for presence and degree of vesicoureteral reflux
Classification #
Uncomplicated UTI(8):
- Acute cystitis occurring in otherwise healthy patients without functional or anatomical urinary tract abnormalities
Complicated UTI:
- Patients with functional or anatomical urinary tract abnormalities that predisposes them to UTIs
- UTIs resulting in pyelonephritis and UTIs occurring in pregnancy
Management #
Approximately 20% of E. coli urine isolates from adults in the community are resistant to trimethoprim2
Sepsis and septic shock from UTI9
Gentamicin IV over 3 to 5 minutes;
- Septic shock or requiring intensive care support, without known or likely pre-existing kidney impairment: 7 mg/kg, for the first dose
- Septic shock or requiring intensive care support, with known or likely pre-existing kidney impairment: 4 to 5 mg/kg, for the first dose
- Septic shock and not requiring intensive care support: 4 to 5 mg/kg intravenously, for the first dose
PLUS
Amoxicillin 2 g IV, 6-hourly OR Ampicillin 2 g IV, 6-hourly
Pyelonephritis – Severe10
Severe: fever (38°C or higher), systemic features (eg tachycardia, nausea, vomiting), or sepsis or septic shock
Gentamicin IV [call-out box for gentamicin dosing guide]
PLUS
Amoxicillin 2 g IV, 6 hourly OR Ampicillin 2 g IV, 6 hourly
If gentamicin is contraindicated:
Ceftriaxone 1 g IV daily OR Cefotaxime 1 g IV 8 hourly
Use targeted therapy once urine MCS has resulted. If sensitivity results are not available by 72 hours and empirical intravenous therapy is still required, use ceftriaxone or cefotaxime regime as above.
Switch to oral ‘non-severe pyelonephritis’ therapy once the patient is clinically stable. The total duration of therapy (intravenous + oral) is 10 to 14 days, depending on clinical response.
Pyelonephritis – Non-severe10
Non-severe: no fever (38°C or higher), systemic features (eg tachycardia, nausea, vomiting), or sepsis or septic shock.
Empirical therapy:
Amoxycillin/clavulanic acid 875/125 mg orally, 12-hourly for 14 days
If clinical response is rapid, stop therapy after 10 days
Penicillin hypersensitivity:
Ciprofloxacin 500 mg orally, 12-hourly for 7 days
Modify empirical treatment to sensitive antibiotics when urine MCS result
Targeted therapy:
Amoxicillin 500 mg orally, 8 hourly
OR
Trimethoprim 300 mg orally, daily
OR
Cefalexin 500 mg orally, 6 hourly
OR
Trimethoprim / Sulfamethoxazole 160/800 mg orally, 12hourly
If clinical response is rapid, stop therapy after 10 days, otherwise continue for 14 days
If resistance to all of the above drugs is confirmed or the pathogen is Pseudomonas aeruginosa, use:
Ciprofloxacin 500 mg orally, 12 hourly for 7 days
Cystitis11
Empirical therapy:
Trimethoprim 300 mg orally, daily for 3 days OR Nitrofurantoin 100 mg orally, 6 hourly for 5 days
If trimethoprim and nitrofurantoin cannot be used, use:
Cefalexin 500 mg orally, 12 hourly for 5 days
For male patients, use the above empirical therapy for 7 days.
Targeted therapy:
Only use targeted therapy if urine MCS shows the pathogen is resistant to empirical therapy and symptoms are not improving.
Amoxicillin 500 mg orally, 8 hourly for 5 days
OR
Trimethoprim / Sulfamethoxazole 160/800 mg orally, 12 hourly for 3 days
Amoxycillin/clavulanic acid 500/125 mg orally, 12 hourly for 5 days
For male patients, use the above targeted therapy for 7 days.
If the pathogen is resistant to these drugs, refer to your infectious diseases team
Cystitis in Pregnancy12
- Asymptomatic bacteriuria screened for at the 12–16-week gestation antenatal visit
- Treated with antibiotics during pregnancy
- Untreated bacteriuria in pregnancy – associated with a 20 to 30% increased risk of developing pyelonephritis in later pregnancy
- Untreated bacteriuria also associated with preterm birth and low birth weight
If Streptococcus agalactiae (group B streptococcus [GBS]) is detected in urine at any stage of pregnancy, intrapartum prophylaxis for GBS is usually indicated
Empirical therapy:
Nitrofurantoin 100 mg orally, 6 hourly for 5 days OR Cefalexin 500 mg orally, 12 hourly for 5 days
If patient is in their second of third trimester, trimethoprim can be used safely
Trimethoprim 300 mg orally, daily for 3 days
Targeted therapy:
Amoxicillin 500 mg orally, 8 hourly for 5 days
OR
Amoxycillin/clavulanic acid 500/125 mg orally, 12 hourly for 5 days
For pregnant women with recurrent UTIs, consider prophylaxis:
Cefalexin 250 mg orally, at night for the remainder of the pregnancy
OR
Nitrofurantoin 50 mg orally, at night for the remainder of the pregnancy
Empirical antibiotic therapy for pyelonephritis during pregnancy remains the same as non-pregnant individuals.
Targeted therapy:
Amoxicillin 500 mg orally, 8 hourly
OR
Cefalexin 500 mg orally, 6 hourly
OR
Amoxycillin/clavulanic acid 875/125 mg orally, 12 hourly
OR
Trimethoprim 300 mg orally, daily
The total duration of therapy (IV + oral) is 10-14 days, depending on clinical response
- Urine MCS re-testing recommended to confirm infection resolution
- If bacteriuria is persistent, prophylactic antibiotics should be considered
References #
- Brusch JL, Bavaro MF, Tessier JM. Medscape. Urinary Tract Infection (UTI) and Cystitis (Bladder Infection) in Females. 2020 [updated 2020 Jan 2; cited 2021 Oct 25]. Available from: https://emedicine.medscape.com/article/233101-overview
- eTG complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2019. Antibiotic choice for urinary tract infection in adults; [updated 2019 April; cited 2021 Oct 25]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=uti-adults-antibiotic-choice&guidelineName=Antibiotic#toc_d1e47
- Lewington A, Lee UJ. BMJ Best Practice. Urinary Tract Infections in Women [Internet]. BMJ Publishing Group Limited; 2021 [updated 2021 Jun 23; cited 2021 Oct 25]. Available from: https://bestpractice.bmj.com.acs.hcn.com.au/topics/en-gb/3000120/epidemiology#riskFactors
- Benton TJ. BMJ Best Practice. Urinary Tract Infections in Men [Internet]. BMJ Publishing Group Limited; 2020 [updated 2020 Dec 22; cited 2021 Oct 25]. Available from: https://bestpractice.bmj.com.acs.hcn.com.au/topics/en-gb/76/history-exam#riskFactors
- Chung A. Bacterial cystitis in Women. Australian Family Physician. 2010 May 2;39(5):295-298.
- McNulty C. Diagnosis of urinary tract infections: quick reference tool for primary care. [Internet]. London: Public Health England; 2020 Mat [updated 2020 October; cited 2021 Oct 25]. Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/927195/UTI_diagnostic_flowchart_NICE-October_2020-FINAL.pdf
- Santos JD, Goilav B, Kaskel F, Jackson MA, VanDerVoode R. BMJ Best Practice. Urinary Tract Infections in Children [Internet]. BMJ Publishing Group Limited; 2021 [updated 2021 Oct 8; cited 2021 Oct 25]. Available from: https://bestpractice.bmj.com.acs.hcn.com.au/topics/en-gb/789/investigations
- Hooton TM, Gupta K. Acute Simple Cystitis in Women. In: Calderwood SB, Bloom A, editors.; UpToDate. [Internet]. UpToDate Inc; 2021. [updated 2021. Mar 15; cited 2021 Oct 25]. Available from: https://www.uptodate.com/contents/acute-simple-cystitis-in-women
- eTG complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2019. Sepsis and septic shock from a urinary tract source in adults; [updated 2019 April]; cited 2021 Oct 25]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=sepsis-urinary-tract-source-adults#toc_d1e47
- eTG complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2019. Acute pyelonephritis in adults; [updated 2019 April; cited 2021 Oct 25]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=acute-pyelonephritis-adults#toc_d1e100
- eTG complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2019. Acute cystitis in adults; [updated 2019 April; cited 2021 Oct 25]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=acute-cystitis-adults#toc_d1e143
- eTG complete [Internet]. Melbourne (Vic): Therapeutic Guidelines Ltd; 2019. Urinary tract infection and bacteriuria in pregnancy; [updated 2019 April; cited 2021 Oct 25]. Available from: https://tgldcdp.tg.org.au.acs.hcn.com.au/viewTopic?topicfile=urinary-tract-infection-pregnancy#toc_d1e47
Contributors
Reviewing Consultant/Senior Registrar
Dr Aashima Juneja
Dr Alice Liu