URINARY TRACT INFECTION

Urinary tract infection (UTI)
Definitions :
UTI is a bacterial infection of the urine (>105 colony-forming units/ml of urine), which may involve the bladder (cystitis) or kidney (pyelonephritis).

Classification
Children may be asymptomatic or symptomatic. It may be the first (intial) infection, or recurrent UTI due to persistence of the causative organism and re-infection, or an unresolved infection due to inadequate treatment.

Incidence
Up to age 1, the incidence in boys is higher than girls (males 2.7%:females 0.7%), but thereafter, the incidence in girls becomes greater (school age: males 1%:females 1 - 3%).

Pathology
Common bacterial pathogens are Escherichia coli (E. coli), Enterococcus, Pseudomonas, Klebsiella, Proteus, and Staphylococcus epidermis. Bacteria enter via the urethra to cause cystitis, and ascending infection causes pyelonephritis. Alternatively, there can be haematogenous spread from other systemic infections.

Risk factors
- Age. Neonates and infants have increased bacterial colonization of the periurethral area and an immature immune system.
- Vesicoureteric reflux (VUR)
- Genitourinary abnormalities (pelviureteric or vesicoureteric obstruction; ureterocele; posterior urethral valves).
- Voiding dysfunction (abnormal bladder activity, compliance, or emptying).
- Gender (female > male after 1 year old).
- Foreskin. Uncircumcised boys have a 10-fold higher risk of UTI in the first year due to bacterial colonization of the glans and foreskin.
- Faecal colonization (contributes to perineal bacterial colonization).

Presentation
Fever, irritability, vomiting, diarrhoea, poor feeding, suprapubic pain, dysuria, voiding difficulties, incontinence, flank pain.

Investigation
Diagnosis is made on urine analysis and culture. In young children, a catheterized urine specimen or a suprapubic aspirate is most accurate (bag specimens are less reliable due to skin flora contamination). In toilet trained children, a mid-stream specimen can be collected.

Imaging
UTI in children <5 years; febrile UTI; infection in non-sexually active boys; and girls (>5 years) with two or more episodes of cystitis require renal tract imaging.
- Ultrasound scan identifies bladder and kidney abnormalities.
- Micturating cystourethrogram (MCUG) demonstrates urethral and bladder anomalies, VUR, and ureteroceles.
- DMSA (dimercaptosuccinic acid) renogram can demonstrate and monitor renal scarring.

Management
Empirical treatment should be started if infection is suspected. Children <3 months old with severe infection or pyelonephritis should receive broad-spectrum intravenous antibiotics (gentamicin and ampicillin) until antibiotic sensitivities are available. Older children, and infants tolerating feeds can be given oral antibiotics (cephalosporins, or nitrofuratoin and trimethoprim-sulphamethoxide after 2 months old).

Complications
Neonates and young children have an increased risk of associated renal involvement and subsequent renal scarring, which can result in hypertension and renal failure.