Investigating Urinary Tract Infections

In most cases the urinary tract infection (UTI) occurs in a child with a normal renal tract and does not cause any lasting damage. In one third of cases there may be an anatomical congenital abnormality which predisposes to UTI by causing stasis of urine in an obstructed or refluxing urinary system (vesicoureteric reflux). Recurrent urinary infections can cause renal parenchymal scarring which may lead to complications of hypertension and renal impairment. This can occasionally cause end-stage renal failure. For this reason there are recommendations regarding investigation of children with UTI:

Initial Management

• Child <3 months with signs of any sepsis: investigate with full septic screen including urine sample for microscopy, culture and sensitivities (MC&S) and treat with IV antibiotics
  
• Child 3 months to 3 years with signs of possible UTI: send urine sample MC&S and start antibiotics
  
• Child >3 years with possible UTI:
  
• Use urine dipstick analysis:
  
  
  
  • nitrite (+) = probable UTI, send urine MC&S and start antibiotic
    
  • leucocyte (+) but nitrite (–) = equivocal, send urine MC&S
  
  
• Do not start antibiotic unless good clinical evidence of UTI
  
• Both leucocyte (–) and nitrite (–) = negative, do not send for culture, do not start antibiotics.

Further Investigation

Further investigation for anatomical problems and scarring depends on the child’s age and whether there are clinical features of more severe, recurrent or atypical infection. The aim is to screen children at higher risk of VUR.

The level of further imaging depends on the child’s age and severity of symptoms. A young baby with UTI is at high risk of reflux and should have full imaging with USS DMSA and MCUG. An older child with mild symptoms in whom infection responds quickly to antibiotics may need no further imaging.

Renal Anomalies

Congenital renal anomalies are common (8/1000 live births). Less than 5% of these will have long-term renal impairment.

• Solitary kidney: A single kidney due to unilateral renal agenesis.
  
• Ectopic kidney: Abnormal migration during embryogenesis leads to a pelvic or horseshoe kidney.
  
• Multicystic dysplastic kidney: The kidney is non-functioning and usually involutes and disappears by school age.
  
• Autosomal dominant polycystic kidney disease (ADPKD): Occurs in 1 in 1000 children and adults. Small cysts are present throughout the kidney. The enlarged kidneys may cause haematuria, hypertension and renal failure later in adult life.
  
• Autosomal recessive polycystic kidney disease (ARPKD): This rare condition (1 in 20 000) is often diagnosed antenatally as the large, cystic kidneys do not produce adequate urine, leading to reduced amniotic fluid and secondary pulmonary hypoplasia. If the child survives the neonatal period they develop end-stage renal failure early in childhood.

Urological Abnormalities

Obstructive uropathy may be due to an obstruction at the level of the renal pelvis, the junction of the ureter with the bladder or at the bladder outlet. Obstructive uropathy can predispose to UTI and if severe can lead to renal impairment or failure.

• Pelviureteric obstruction is due to abnormal tissue or external compression at the point the renal pelvis joins the ureter. 75% improve without the need for surgical intervention.
  
• Posterior urethral valves occurs in 1 in 10 000 male infants. It is due to persistence of an embryological fold across the urethra, causing bladder hypertrophy, bilateral hydronephrosis and renal impairment.
  
• Hypospadias: The external urinary meatus opens on the ventral side of the penis. It may be mild, needing no treatment, or severe, requiring surgical repair. For this reason parents should be advised not to have the child circumcised, so that the foreskin tissue can be used in reconstructive surgery.
  
• Phimosis: The foreskin is non-retractile. This is normal in infancy and requires surgery only if there is an obstruction problem.
  
• Paraphimosis: The foreskin becomes trapped behind the glans causing pain and swelling. It is usually reducible without surgery.

Circumcision is most commonly performed for persistence of these problems, or for cultural or religious reasons.

Vesicoureteric Reflux

The retrograde flow of urine from the bladder into the ureters can cause hydronephrosis and predispose to UTI, pyelonephritis, hypertension or end-stage renal failure. VUR occurs because of an abnormally short and straight insertion of the ureters through the wall of the bladder, so that they are not properly occluded during bladder contraction. The severity of VUR is graded depending on extent of reflux and degree of dilatation of ureters, renal pelvis and calyces. VUR can be managed with conservative treatment (surveillance monitoring and antibiotics for infection). Around 50% resolve but surgery may be needed if there are breakthrough infections or deteriorating renal function.