Imaging of urinary tract infection in the adult

The diagnosis of urinary tract infection (UTI) in the adult is primarily based on typical patient symptomatology and urinary evaluation for the presence of bacteria and white blood cells. Uncomplicated UTI usually does not require radiological evaluation unless it is recurrent. Imaging should, in general, be reserved for those patients in whom conventional treatment has failed or those who have recurrent or unusually severe symptoms. Patients with conditions predisposing to infection, or complications thereof, such as diabetes mellitus or immunocompromised states, may also benefit from early imaging. If pyonephrosis is suspected, early imaging and possible urgent drainage is also warranted. Intravenous urogram and ultrasound have traditionally been used in the assessment of these patients, allowing detection of calculi, obstruction and incomplete bladder emptying. These imaging techniques, while useful, have limitations in the evaluation of renal inflammation and infection in the adult. Computerised tomography has now become accepted as a more sensitive modality for diagnosis and follow-up of complicated renal tract infection. Contrast-enhanced CT allows different phases of excretion to be studied and can define extent of disease and identify significant complications or obstruction. Nuclear medicine has a limited role in the evaluation of urinary tract infection in adults. Its main role is in the assessment of renal function, often prior to surgery. Magnetic resonance imaging has a limited but increasing role. It is particularly useful in those with iodinated contrast allergies, offering an ionising radiation free alternative in the diagnosis of both medical and surgical diseases of the kidney.