Urinary Tract Infection Flashcards
What
Lower urinary tract infections (UTIs) involve infection in the bladder, causing cystitis (inflammation of the bladder). They can spread up to the kidneys and cause pyelonephritis. Urinary tract infections are far more common in women, where the urethra is much shorter, making it easy for bacteria to get into the bladder.
The primary source of bacteria for urinary tract infections is from the faeces. Normal intestinal bacteria, such as E. coli, can easily make the short journey to the urethral opening from the anus. Sexual activity is a crucial method for spreading bacteria around the perineum. Incontinence or poor hygiene can also contribute to the development of UTIs.
Urinary catheters are a key source of infection, and catheter-associated urinary tract infections tend to be more significant and challenging to treat.
Present
Lower urinary tract infections present with:
Dysuria (pain, stinging or burning when passing urine)
Suprapubic pain or discomfort
Frequency
Urgency
Incontinence
Haematuria
Cloudy or foul smelling urine
Confusion is commonly the only symptom in older and frail patients
TOM TIP: It is important to distinguish between patients with a lower urinary tract infection and those with pyelonephritis. Pyelonephritis is generally a more serious condition with significant complications, including sepsis and kidney scarring. Suspect pyelonephritis in patients with:
Fever
Loin/back pain
Nausea/vomiting
Renal angle tenderness on examination
Diagnosis
Urine Dipstick
Nitrites – gram-negative bacteria (such as E. coli) break down nitrates, a normal waste product in urine, into nitrites. The presence of nitrites suggest bacteria in the urine.
Leukocytes are white blood cells. It is normal to have a small number of leukocytes in the urine, but a significant rise can result from an infection or other cause of inflammation. Leukocyte esterase is tested on a urine dipstick, which is a product of leukocytes and indicates the number of leukocytes in the urine.
Red blood cells in the urine indicate blood. Microscopic haematuria is where blood is identified on a urine dipstick but not seen when looking at the sample. Macroscopic haematuria is where blood is visible in the urine. Haematuria is a common sign of infection but can also be present with other causes, such as bladder cancer or nephritis.
Nitrites are a better indication of infection than leukocytes. The NICE clinical knowledge summaries (2020) suggest that the presence of nitrites or leukocytes plus red blood cells indicate that the patient is likely to have a UTI.
If both are present, the patient requires treatment for a UTI. If only nitrites are present, it is worth treating as a UTI. If only leukocytes are present, the patient should not be treated as a UTI unless there is clinical evidence they have one.
A midstream urine (MSU) sample sent for microscopy, culture and sensitivity testing will determine the infective organism and the antibiotics that will be effective in treatment. Not all patients with an uncomplicated UTI require an MSU. This is important in:
Pregnant patients
Patients with recurrent UTIs
Atypical symptoms
When symptoms do not improve with antibiotics
Causes
The most common cause of UTI is Escherichia coli. E. coli are gram-negative, anaerobic, rod-shaped bacteria that are part of the normal lower intestinal microbiome. It is found in faeces and can easily spread to the bladder.
Other causes:
Klebsiella pneumoniae (gram-negative anaerobic rod)
Enterococcus
Pseudomonas aeruginosa
Staphylococcus saprophyticus
Candida albicans (fungal)
Antibiotics
Follow local guidelines. An appropriate initial antibiotic in the community would be:
Trimethoprim (often associated with high rates of bacterial resistance)
Nitrofurantoin (avoided in patients with an eGFR <45)
Alternatives:
Pivmecillinam
Amoxicillin
Cefalexin
Duration of Antibiotics
3 days of antibiotics for simple lower urinary tract infections in women
5-10 days of antibiotics for immunosuppressed women, abnormal anatomy or impaired kidney function
7 days of antibiotics for men, pregnant women or catheter-related UTIs
It is worth noting that NICE recommend changing the catheter when someone is diagnosed with a catheter-related urinary tract infection.
Pregnancy
Urinary tract infections in pregnancy increase the risk of pyelonephritis, premature rupture of membranes and pre-term labour.
Management in Pregnancy
Urinary tract infection in pregnancy requires 7 days of antibiotics. All women should have an MSU for microscopy, culture and sensitivity testing.
The antibiotic options are:
Nitrofurantoin (avoid in the third trimester)
Amoxicillin (only after sensitivities are known)
Cefalexin
Nitrofurantoin needs to be avoided in the third trimester as there is a risk of neonatal haemolysis (destruction of the neonatal red blood cells).
Trimethoprim needs to be avoided in the first trimester as it works as a folate antagonist. Folate is essential in early pregnancy for the normal development of the fetus. Trimethoprim in early pregnancy can cause congenital malformations, particularly neural tube defects (e.g., spina bifida). It is not known to be harmful later in pregnancy but is generally avoided unless necessary.
Urinary tract infections in pregnant women increase the risk of
preterm delivery
Pyelonephritis symptoms
Fever (more prominent than in lower urinary tract infections)
Loin, suprapubic or back pain (this may be bilateral or unilateral)
Looking and feeling generally unwell
Vomiting
Loss of appetite
Haematuria
Renal angle tenderness on examination
Manage UTI in Pregnancy
Urinary tract infection in pregnancy requires 7 days of antibiotics.
The antibiotic options are:
Nitrofurantoin (avoid in the third trimester)
Amoxicillin (only after sensitivities are known)
Cefalexin
Nitrofurantoin needs to be avoided in the third trimester as there is a risk of neonatal haemolysis (destruction of the neonatal red blood cells).
Trimethoprim needs to be avoided in the first trimester as it is works as a folate antagonist. Folate is important in early pregnancy for the normal development of the fetus. Trimethoprim in early pregnancy can cause congenital malformations, particularly neural tube defects (i.e. spina bifida). It is not known to be harmful later in pregnancy, but is generally avoided unless necessary.
Manage UTI in Paediatrics
All children under 3 months with a fever should start immediate IV antibiotics (e.g. ceftriaxone) and have a full septic screen, including blood cultures, bloods and lactate. A lumbar puncture should also be considered.
Oral antibiotics can be considered in children over 3 months if they are otherwise well. Children with features of sepsis or pyelonephritis will require inpatient treatment with IV antibiotics. Always follow local guidelines. Typical antibiotic choices in urinary tract infections in children are:
Trimethoprim
Nitrofurantoin
Cefalexin
Amoxicillin
Investigate Recurrent UTI in Paeds
Recurrent UTIs should be investigated for an underlying cause and renal damage. This is a summary of the NICE guidelines on urinary tract infections in under 16s. Please read the full guidelines before treating patients.
Ultrasound Scans
All children under 6 months with their first UTI should have an abdominal ultrasound within 6 weeks, or during the illness if there are recurrent UTIs or atypical bacteria
Children with recurrent UTIs should have an abdominal ultrasound within 6 weeks
Children with atypical UTIs should have an abdominal ultrasound during the illness
DMSA (Dimercaptosuccinic Acid) Scan
DMSA scans should be used 4 – 6 months after the illness to assess for damage from recurrent or atypical UTIs. This involves injecting a radioactive material (DMSA) and using a gamma camera to assess how well the material is taken up by the kidneys. Where there are patches of kidney that have not taken up the material, this indicates scarring that may be the result of previous infection.
Vesico-Ureteric Reflux (VUR)
Vesico-ureteric reflux (VUR) is where urine has a tendency to flow from the bladder back into the ureters. This predisposes patients to developing upper urinary tract infections and subsequent renal scarring. This is diagnosed using a micturating cystourethrogram (MCUG).
Management of vesico-ureteric reflux depends on the severity:
Avoid constipation
Avoid an excessively full bladder
Prophylactic antibiotics
Surgical input from paediatric urology
Micturating Cystourethrogram (MCUG)
Micturating cystourethrogram (MCUG) should be used to investigate atypical or recurrent UTIs in children under 6 months. It is also used where there is a family history of vesico-ureteric reflux, dilatation of the ureter on ultrasound or poor urinary flow. A MCUG is used to diagnose VUR.
It involves catheterising the child, injecting contrast into the bladder and taking a series of xray films to determine whether the contrast is refluxing into the ureters. Children are usually given prophylactic antibiotics for 3 days around the time of the investigation.
Pyelonephritis Management
NICE recommend the following first line antibiotics for 7-10 days when treating pyelonephritis in the community:
Cefalexin
Co-amoxiclav
Trimethoprim
Ciprofloxacin
