Urinary Tract Infections

The urinary tract includes the urethra, bladder, ureters and kidneys. Urinary tract infections are infections anywhere along this pathway.

Acute pyelonephritis is when the infection affects the tissue of the kidney. It can lead to scarring in the tissue and consequently a reduction in kidney function.

Cystitis means inflammation of the bladder, and can be the result of a bladder infection.



Fever may be the only symptom of a urinary tract infection, especially in young children. Always consider (and exclude) a urinary tract infection in a child with a temperature, unless there is a clear alternative source of infection.

Babies will present with very non-specific symptoms:

  • Fever
  • Lethargy
  • Irritability
  • Vomiting
  • Poor feeding
  • Urinary frequency

Signs and symptoms in older infants and children are more specific:

  • Fever
  • Abdominal pain, particularly suprapubic pain
  • Vomiting
  • Dysuria (painful urination)
  • Urinary frequency
  • Incontinence


Acute Pyelonephritis

The diagnosis of acute pyelonephritis is made if either there is:

  • A temperature greater than 38°C
  • Loin pain or tenderness

This is a very important point to note, as it affects the way you would investigate the child for recurrent infections.


Urine Dipstick

The ideal urine sample is a clean catch sample, avoiding contamination. This can be tricky in younger children and babies, particularly girls. This often involves the parent sat with the infant without a nappy and a urine pot held ready to catch the sample if it occurs. A clean catch sample is important to avoid contamination and unreliable microbiology results.

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 – leukocytes are white blood cells. There are normally a small number of leukocytes in the urine, however a significant rise can be the result of an infection or another cause of inflammation. A urine dipstick tests for leukocyte esterase, a product of leukocytes that give an indication about the number of leukocytes in the urine.

Nitrites are a better indication of infection than leukocytes. If both are present the patient should be treated as 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.

If nitrites or leukocytes are present, the urine should be sent to the microbiology lab. If neither are present the patient is unlikely to have a UTI.

Send a midstream urine (MSU) sample to the microbiology lab to be cultured and have sensitivity testing. 



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


Investigating Recurrent UTIs

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.


Last updated August 2019
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