Urinary tract infection in pre-school children

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16.4 Urinary tract infection in pre-school children

1 Urinary tract infection is common and potentially serious.

2 Septicaemia may occur in babies.

3 Renal scarring is a serious and potentially preventable complication.

4 Urinary tract infection should be considered in all febrile infants and young children, as well as babies who are non-specifically unwell.

5 In young children, urinary tract infection cannot be diagnosed reliably or excluded on clinical grounds.

6 Dipstick urinalysis is an unreliable method of ruling out urinary tract infection in infants.

Introduction

Bacterial infection of the urinary tract (UTI) is common in the paediatric age group. Its significance is greatest in young children, particularly in the first year or two of life, where the high incidence of upper tract infection (pyelonephritis) and the presence of immature kidneys lead to significant potential for renal scarring (reflux nephropathy). It is unlikely that new scarring occurs after age 5 years.

Data from Sweden suggest that in the first 2 years of life, up to 3% of infants may suffer UTI. Between 1 and 10 years of age 3–8% of girls and < 1% of boys will have at least one urine infection. It is important to remember that recurrences are common. UTI is more frequent in boys than girls in the first months of life, partly because of a higher incidence of obstruction including pelviureteric junction obstruction, thereafter occurring significantly more often in girls (Fig. 16.4.1).

Fig. 16.4.1 Epidemiology of UTI in childhood. Cases recorded in Gothenburg 1960–1966.

Source: Winberg J, Andersen HJ, Bergström T, et al. Acta Paediatrica Scandinavia Supplement 1974;63(Suppl. 252):1?20.

UTI is caused by organisms normally resident in the gut. It is thus an ascending infection that may affect the bladder (cystitis) or upper renal tract (pyelonephritis), which may in turn result in scarring. Neonates are unusual as they may also develop UTI following haematogenous dissemination of organisms.

Renal involvement is associated with:

• young age (especially <1 year);

• symptoms > 5 days;

• systemic upset, fever, leucocytosis;

• presence of vesicoureteric reflux (VUR) or other anatomical abnormality.

Long-term complications of renal scarring include: pregnancy-associated problems; hypertension; and, rarely, chronic renal insufficiency (see prognosis section below).

History and examination

In infants and young children with UTI, the clinical history is frequently non-specific and may include irritability, jaundice (neonates), poor feeding or fever without apparent source. Symptoms and signs become more specific with increasing age (Table 16.4.1).

Don’t forget to obtain a family history of renal tract disease, in particular regarding UTIs, VUR (probably an autosomal dominant condition) and renal impairment.

Physical examination of young children with UTI is often unremarkable or non-specifically abnormal. Septicaemia, however, does occur with UTI in infancy and must be considered in babies up to around 6 months of age. Fever is the best clinical marker of pyelonephritis in infants with UTI, but is non-specific.

Diagnosis

A reliable urine sample is required to establish the diagnosis of UTI. In older children this is usually accomplished by obtaining a midstream sample. Difficulties arise in children too young to have been toilet trained, who are also the group at highest risk for pyelonephritis and renal scarring.

In infants and toddlers, urine bag samples are unreliable (very high false-positive rate) and should not be used. Clean catch samples are more reliable and are the preferred method for non-invasive urine collection. If samples are required urgently, bladder catheterisation is the most reliable method, though those familiar with the technique can consider suprapubic aspiration (SPA). The yield from SPA is markedly improved by using ultrasound to confirm a full bladder.

Samples should be sent to the laboratory for urinalysis, microscopy and culture. Findings supportive of the diagnosis of UTI include presence of leucocytes and organisms on microscopy and leucocyte esterase and nitrites on dipstick urinalysis. Organisms may be seen on Gram stain. In centres without 24-hour laboratory services, after-hours samples should be sent using a urine dip-slide.

Dipstick urinalysis may be helpful in making a provisional diagnosis of UTI. However, a negative result does not rule out UTI in infancy. One study showed that urinalysis was normal in 50% of infants <8 weeks with confirmed UTI. Another study suggested that dipstick urinalysis was a reliable method of ruling out UTI only after age 2 years.

The traditional definition of pyuria is >5 white blood cells (WBC) per high-power field (centrifuged urine). Another definition is >10 WBC mm^–3 (uncentrifuged urine).

The definition of significant bacteriuria is guided by the method by which the urine specimen was collected (Table 16.4.2), though on occasion genuine UTI may be present with lower colony counts than would usually be considered significant, especially in babies – interpret results in light of history and clinical findings.

Method of collection Colony forming unit count (CFU mL^–1) Clean catch > 10⁵ Catheter >5 × 10⁴ Suprapubic >0

Treatment

ED treatment recommendations for UTI vary. However, one approach is as follows.

Age <6 months

• Admit all for intravenous (IV)/intramuscular (IM) antibiotics (septicaemia occurs in this age group).

• Admit to medical ward (observation ward only if systemically well).

• If discharged from observation ward, arrange general practitioner (GP) or ED follow up at 24–48 hours.

• Ensure urine culture and sensitivity results are checked at 48–72 hours.

Age 6–12 months

• If systemically unwell, admit to observation ward or medical ward for IV/IM antibiotics.

• If not systemically unwell, consider single IM/IV dose of ceftriaxone or gentamicin, followed by oral antibiotics.

• Arrange GP or ED follow up at 24–48 hours.

• Ensure urine culture and sensitivity results are checked at 48–72 hours.

Age >12 months

• Treat on clinical merits, i.e. admit or allow home, parenteral or oral antibiotics.

• Overnight admission to observation ward for IV/IM antibiotics may be worth considering if unwell.

• Ensure urine culture and sensitivity results are checked at 48–72 hours.

Duration of treatment?

• Infants up to 12 months: treat for 10 days at full dose.

• Older children: generally treat for 5–10 days at full dose.

• Courses as short as 3 days may be used in older children with uncomplicated lower tract UTI.

Management after discharge from ED or observation wards

Most centres will have a referral, management and investigation protocol which should be followed. Many of these are based on the National Institute for Clinical Excellence Guidelines from the United Kingdom,¹ though significant variation exists from place to place. In the absence of local guidelines, the following approach is reasonable.

Arrange a ‘proof of cure’ urine culture after stopping antibiotic.

In pre-school children (both sexes), following the first documented UTI (or if previous UTI not investigated), start low-dose nocturnal prophylactic antibiotics. Co-trimoxazole (because of its long shelf life) and nitrofurantoin are reasonable choices. The dose is 1–2 mg kg^–1 at night for both drugs (expressed as the trimethoprim component in the case of co-trimoxazole). Trimethoprim suspension is unavailable commercially in Australia, but is a better choice than co-trimoxazole in countries where it is readily obtainable.

A practical note – after the full course of treatment, if any antibiotic is left over, continue this as a nocte dose until finished, and then change to a nocte dose of the chosen prophylactic antibiotic.

Arrange a renal tract ultrasound (although some would restrict this to children <3 years), and refer to medical out-patients, hospital UTI clinic or paediatric nephrology clinic (depending on local organisation) all those discharged home from ED/observation wards who have not previously been investigated.

It is generally not necessary to book other imaging studies as consultants will differ in the investigations that they prefer, e.g. micturating cystourethrogram (MCUG) and/or dimercaptosuccinic acid (DMSA) isotope scan, though this can be expedited by speaking to the consultant or unit to whom the child has been referred.

Prevention

The ‘basics’ of good fluid intake, regular and complete voiding, avoidance of constipation and proper (front to back) bottom wiping (in toilet-trained females) should be encouraged in order to reduce the likelihood of repeat infections. There is also some evidence of benefit from the regular use of cranberry juice (which acidifies urine and reduces bladder wall adhesiveness). Prophylactic antibiotics should be considered in cases of VUR in pre-school children, recurrent pyelonephritis, recurrent symptomatic UTI in older children and in pre-school children awaiting renal tract imaging.

Controversies and future directions

‘There is no subject in which there is so little uniformity of opinion and so much confusion.’ This statement made in 1916 is seemingly just as pertinent in the early 21st century, with many questions about paediatric UTI management still the subject of debate and controversy. On the specific subject of VUR, one author, considering ‘the effect of scientific evidence on clinical decision making in children with VUR during the past 40 years’ (since its description), suggests that ‘reported data have been overlooked in favour of unfounded speculation or clinical tradition’.⁵

1 NICE Guidelines. Urinary tract infection: diagnosis, treatment and long-term management of urinary tract infection in children. Available at http://www.nice.org.uk/CG054 [accessed 21.10.10]

2 Smellie J., Edwards D., Hunter N., et al. Vesico-ureteric reflux and renal scarring. Kid IntSuppl. 1975;4:65-72.

3 Malek R.S., Svensson J., Neves R.J., Torres V.E. Vesicoureteral reflux in the adult. III. Surgical correction: benefits. J Urol. 1983;130:882-886.

4 Noe H.N. The current status of screening for vesicoureteral reflux. Paediatr Nephrol. 1995;9:638-641.

5 Hewitt I.K., Zucchetta P., Rigon L., et al. Early treatment of acute pyelonephritis in children fails to reduce renal scarring: data from the Italian renal infection study trials. Pediatrics. 2008;122(3):486-490.

Further reading

Bachur R., Caputo G.L. Bacteraemia and meningitis among infants with urinary tract infection. Paediatr Emerg Care. 1995;11:280-284.

Crabtree E.G., Cabot H. Colon bacillus pyelonephritis: Its nature and possible prevention. Transactions of the Section of Genitourinary Diseases of the American Medical Association, vol 57. 1916:209-217.

Crain E.F., Gershel J.C. Urinary tract infections in febrile infants younger than 8 weeks. Paediatrics. 1990;86:363-367.

Doley A., Neligan M. Is a negative dipstick urinalysis good enough to exclude urinary tract infection in paediatric ED patients? Emerg Med. 2003;15:77-80.

Hodson E.M., Wheeler D.M., Vimalchandra D., et al. Interventions for primary vesicoureteric reflux. Cochrane Database Syst Rev. (3):2007. CD001532

Jakobsson B., Esbjorner E., Hansson S. Minimum incidence and diagnostic rate of first urinary tract infection. Paediatrics. 2000;106:620-621.

Kinney A.B., Blount M. Effect of cranberry juice on urinary pH. Nurs Res. 1979;28:287-290.

Montini G., Zucchetta P., Tomasi L., et al. Value of imaging studies after a first febrile urinary tract infection in young children: data from Italian renal infection study 1. Pediatrics. 2009;123(2):e239-e246. Epub 2009 Jan 12

Pollack C.V., Pollack E.S., Andrew M.E. Suprapubic bladder aspiration versus urethral catheterization in infants: Success, efficiency and complication rates. Ann Emerg Med. 1994;23:225-230.

Shihab Z.M. Urinary tract infection. In: Barakat A.Y., editor. Renal disease in children – clinical evaluation & diagnosis. New York: Springer-Verlag; 1990:157-170.

Sobota A.E. Inhibition of bacterial adherence by cranberry juice: Potential for treatment of urinary tract infections. J Urol. 1984;131:1013-1016.

Willis F.R., Geelhoed G.C. Urinary tract infection. In: Management guidelines – Emergency Department. Perth, Western Australia: Princess Margaret Hospital for Children; 2002.

Related

Textbook of Paediatric Emergency Medicine