Renal imaging

The renal tract is investigated mainly to identify the underlying cause in patients with abnormal renal function, renal colic or haematuria. Increasing use of ultrasound and computed tomography has limited the role of plain radiographs, but these are still used in the initial assessment of abdominal colic to evaluate potential renal or bowel abnormalities. Intravenous urography – radiological examination of the urinary tract performed following the intravenous injection of iodinated contrast – is the classical means by which to assess the kidneys and ureters. Ultrasound is often the first imaging modality used to interrogate and follow up renal abnormalities. Computed tomography (CT) can be useful to evaluate renal masses and determine the site of ureteric obstruction by calculi. Magnetic resonance imaging (MRI) is primarily used to assess the renal arteries in patients with suspected renal artery stenosis. CT and MRI can provide images of exceptional detail and resolution beyond the means of other modalities, and are thus often used to characterize and follow renal masses; in addition, images can be obtained in multiple planes. Radionuclide scans can be helpful in the evaluation of renal tract obstruction and provide a functional assessment of the renal tract.