Paediatric Imaging

Infection, urinary tract

Presending symptoms in infancy include voimting, pyrexia, seizures and haematuria. In older children, fever and rigors, as well as frequent dysuria and nocturia can be presenting symptoms. The diagnosis is made by culture of the urine and is usually considered to be proven when there is a pure culture of a single bacterium in a concentration of 10,000 organisms per ml with pyuria.

Urinary tract infections are commoner in girls than boys. There is an increased incidence in siblings. Most urinary tract infections have no anatomical cause but they can be associated with structural renal abnormalities such as hydronephrosis and more commonly with vesicoureteric reflux.

No scheme of investigation is universally accepted. The aim of investigation is to identify structural causes which are surgically remediable and to document renal scarring. Associated structural anomalies are duplex kidneys, bladder diverticula and hydronephrosis. In all children ultrasound is the initial imaging study. Under 1 year, a micturating cystourethrography (MCUG) to exclude reflux is also indicated which should include views of the posterior urethra in boys to exclude urethral abnormalities. A DMSA scan to exclude renal scarring in the presence of reflux and isotope renography to exclude renal obstruction in the presence of hydronephrosis are indicated as appropriate. Intravenous urography plays a small part but can be useful in demonstrating duplex kidneys if these are not satisfactorily demonstrated by other means.

In children over the age of 5, where structural renal abnormalities are much less common, an ultrasound scan together with DMSA scintigraphy to exclude renal scarring would be considered adequate investigation for a first urinary tract infection.

The decision about how to image children with urinary tract infection from the age of one to five and recurrent urine infection over the age of five is a personal one with some opting for comprehensive investigation of urinary tract infection at all ages with others opting for a more conservative approach particularly in the absence of constitutional symptoms (fever, rigors, localised loin pain). Plain radiography of the abdomen to exclude renal calculi is considered valuable by some but is rarely contributory.

Urinary tract infections are treated with antibiotic therapy. Management is by antibiotic prophylaxis for those children with vesicouereteric reflux. This allows time for the resolution of reflux which occurs with increasing maturity in children with low grades of reflux by the age of four to five years. Continuing reflux or higher grades may require reimplantation of the ureter. Surgical management of congenital urinary tract abnormalities is undertaken as appropriate.

Investigation of the urinary tracts following infection (apart from ultrasound) should be postponed until the infection has been cleared as spurious results can be obtained in the presence of acute infection. Indirect cystography to assess the urinary tract and confirm resolution of reflux is an appropriate technique in the older child.

Rarer forms of urinary tract infection includes xanthogranulomatous pyelonephritis and pyonephrosis. Fungal infections including candidiasis, tuberculosis and schistosomiasis are other rare forms of infection. See fungus ball infection

DWP