Urinary Tract Infection

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Diagnosis and reasoning

This 3 year and 6 month old girl has presented with fever, abdominal pain and dysuria, a triad of symptoms suggestive of a urinary tract infection (UTI). This diagnosis is supported by the urinalysis showing increased pus cells, and positive leukocyte esterase and nitrates. The fever is mild, she is non-toxic, and not dehydrated or hemodynamically unstable; nor is renal angle tenderness present, while a full blood count is also within normal parameters. Thus, there appears to be no immediate emergency. The first step in her management should be initiation of empirical antibiotic therapy; however, urine should be sent for culture and antibiotic sensitivity testing beforehand. Note that co-trimoxazole is a good first-line agent in this regard, due to minimal reported drug resistance; ciprofloxacin is best avoided in children, due to safety concerns. An analgesic such as acetaminophen should also be administered for symptomatic relief. The next step is to decide on whether imaging of the urinary tract is warranted. The American Academy of Pediatrics (AAP) states that renal and bladder ultrasonography is mandatory following the first episode of UTI in children under the age of 2 years; however, they have not provided guidance for older age groups. The National Institute for Health and Care Excellence (NICE) guidelines recommend imaging of children over 3 years of age only if there is no response to treatment within 48 hours. Thus, it is justifiable to wait for this time period, and then resort to imaging if there are no signs of recovery. Note in particular that voiding cystourethrography is only indicated if ultrasonography reveals abnormalities of the urinary tract. In general, children with simple UTIs do not require urological referral; this particular child certainly does not need immediate referral. However, if she demonstrates a poor response to treatment, this may be required later.


Urinary tract infections (UTI) are extremely common in pediatric practice; unlike adult UTIs, those in children are often due to underlying congenital abnormalities of urinary tract. Depending on anatomical site of infection, UTIs are subdivided into those of the upper and lower tract; the former includes pyelonephritis, ureteritis and infections of the collecting ducts, while the latter includes cystitis and urethritis. Early diagnosis and treatment of these patients is critical, given the potential for acute complications such as dehydration, pyelonephritis, urosepsis and meningitis, as well as long term complications such as renal insufficiency and renal scarring. The remainder of this monograph pertains to 'febrile' UTIs (i.e. those associated with fever); note that the management of UTIs not associated with fever is different, and depends on the degree and duration of bacteriuria. The evaluation and management of these patients should be based on standard guidelines; in this respect, the American Academy of Pediatrics (AAP) has published literature applicable to children below 2 years of age, while the National Institute for Health and Care Excellence (NICE) guidelines cover children of all ages. These guidelines were formulated due to the high rates of extraneous investigations, and high failure rates in diagnosing complications by primary care physicians. Confirmation of the presence of a UTI should be the first step in these patients. Urine cultures are still the gold standard in this regard, but are hampered by requiring at least 18 hours for detection of bacterial growth. In comparison, biochemical analysis of urine for leukocyte esterase (LE) and nitrates are of good sensitivity, while also being easy to perform, and providing results rapidly. Note that while microscopy of a centrifuged urine specimen has been the standard method of assessing pyuria, recent meta-analyses have failed to show an advantage over LE dipstick tests. The next step in the evaluation should be identification of associated complications, and any underlying congenital abnormalities of the urinary tract; the goal is to achieve this with as few investigations as possible, while minimizing their invasiveness. Both the AAP and NICE guidelines agree that children less than 2 years of age should undergo renal-bladder ultrasonography. The AAP does not provide specific guidance for older children; however, the NICE guidelines recommend that children over 3 years should only be investigated if they present with recurrent, complicated, or atypical disease, or if there is no response to empirical treatment within 48 hours. Note that the goal of ultrasonography is to guide the treatment by detecting if parenchymal damage is present; many of these patients have clinically insignificant vesicoureteric reflux (VUR), which does not need specific management. The above is important to appreciate because 47.5% of these patients demonstrate VUR, but less than 2.6% have high grade reflux (grade 3 and above). Voiding cystourethrography (VCUG) is indicated if ultrasonography reveals hydronephrosis, scarring, obstructive uropathy, masses, or findings suggestive of high grade VUR. Furthermore, children who respond to treatment but who demonstrate abnormal patterns of voiding later should undergo VCUG, as should patients with recurrent UTIs; this is necessary even if sonography is normal. Note that technetium 99m-labeled dimercaptosuccinic acid (DMSA) scanning has emerged as a new modality for identification of complicated upper urinary tract infections, but should be used judiciously. Considering treatment, the AAP recommends antibiotic therapy to be based on local sensitivity patterns where possible; good first-line choices include oral co-trimoxazole or co-amoxiclav, or a cephalosporin such as cefixime, cephalexin, cefprozil, or cefpodoxime. It is important to appreciate that there has been a recent increase in resistance to both amoxicillin, and fluoroquinolones such as ciprofloxacin (which are best avoided anyway, due to safety concerns in children). In children detected to have VUR, the decision as to whether antibiotic prophylaxis is indicated has traditionally been controversial. However, the ongoing randomized intervention for children with vesicoureteral reflux (RVUR) study has showed promising results in this regard, providing evidence that prophylaxis does help preventing recurrent infection. However, this did not appear to reduce the incidence of scarring, or further progression to renal insufficiency.

Take home messages

  1. Urinary tract infections (UTI) are common in childhood, and are often due to underlying congenital abnormalities of the urinary tract.
  2. Early diagnosis and timely management is critical in preventing complications of UTI.
  3. Ultrasonography and VCUG are not indicated in all children presenting with a first UTI.

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