542 CHAPTER 15 Pediatric urology

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 (initial) infection, recurrent UTI due to persistence of the causative organism and reinfection, or an unresolved infection due to inadequate treatment.

Incidence

Up to age 1 year, the incidence in boys is higher than in girls (males 2.7%: females 0.7%). 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 hematogenous 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 (UPJ 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 from bacterial colonization of the glans and foreskin.

•Fecal colonization (contributes to perineal bacterial colonization)

Presentation

UTI patients present with fever, irritability, vomiting, diarrhea, poor feeding, suprapubic pain, dysuria, voiding difficulties, incontinence, and flank pain.

Investigation

Diagnosis is made on urinalysis and culture. In young children, a catheterized urine specimen or a suprapubic aspirate is most accurate (bag specimens are less reliable because of skin flora contamination).

In toilet-trained children, a mid-stream specimen can be collected.

URINARY TRACT INFECTION (UTI) 543

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 identifies bladder and kidney abnormalities.

•Voiding cystourethrogram (VCUG) 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 nitrofurantoin and trimethoprim-sulfamethoxide 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.

544 CHAPTER 15 Pediatric urology

Vesicoureteric reflux (VUR)

Definition

VUR results from abnormal retrograde flow of urine from the bladder into the upper urinary tract.

Epidemiology

Overall incidence in children is >10%, with younger children affected more than older children, girls more than boys (female–male ratio 5:1). VUR occurs more often in Caucasian than in Afro-Caribbean children.

Siblings of an affected child have a 40% risk of reflux, and routine screening of siblings is recommended.

Pathogenesis

The ureter passes obliquely through the bladder wall (1–2 cm), where it is supported by muscular attachments that prevent urine reflux during bladder filling and voiding. The normal ratio of intramural ureteric length to ureteric diameter is 5:1.

Reflux occurs when the intramural length of ureter is too short (ratio <5:1). The degree of reflux is graded I–V (see Fig. 7.1, p. 345). The appearance of the ureteric orifice changes with increasing severity of reflux, classically described as stadium, horseshoe, golf-hole, or patulous.

Classification

•Primary reflux (1%) results from a congenital abnormality of the ureterovesical junction.

•Secondary reflux results from urinary tract dysfunction associated with elevated intravesical pressures. Causes include posterior urethral valves (reflux seen in 50%), urethral stenosis, neuropathic bladder, and detrusor sphincter dyssynergia (DSD).

•VUR is also seen with duplex ureters. The Weigert–Meyer rule states that the lower-pole ureter enters the bladder proximally and laterally, resulting in a shorter intramural tunnel, which predisposes to reflux.

Complications

VUR associated with UTI can result in reflux nephropathy with hypertension and progressive renal failure.

Presentation

Patients have symptoms of UTI, fever, dysuria, suprapubic or abdominal pain, failure to thrive, vomiting, and diarrhea.

Investigation

•Urinalysis and culture to diagnose UTI

•Urinary tract ultrasound scan and VCUG to diagnose and grade reflux and establish reversible causes (Fig. 15.2)

•Urodynamic assessment if suspicious of voiding dysfunction

•DMSA scan to detect and monitor associated renal cortical scarring.