Imaging in diagnosis, treatment, and follow-up of stone patients.

Imaging has an essential role in the diagnosis, management, and follow-up of patients with stone disease. A variety of imaging modalities are available to the practicing urologist, including conventional radiography (KUB), intravenous urography (IVU), ultrasound (US), magnetic resonance urography, and computed tomography (CT) scans, each with its advantages and limitations. Traditionally, IVU was considered the gold standard for diagnosing renal calculi, but this modality has largely been replaced by unenhanced spiral CT scans at most centers. Renal US is recommended as the initial imaging modality for suspected renal colic in pregnant women and children, but recent literature suggests that a low-dose CT scan may be safe in pregnancy. Intraoperative imaging by fluoroscopy or US plays a large part in assisting the urologist with the surgical intervention chosen for the individual stone patient. Posttreatment imaging of stone patients is recommended to ensure complete fragmentation and stone clearance. Plain radiography is suggested for the follow-up of radiopaque stones, with ultrasound and limited IVU reserved for the follow-up of radiolucent stones to minimize cumulative radiation exposure from repeated CT scans. Patients with asymptomatic calyceal stones who prefer an observational approach should have a yearly KUB to monitor progression of stone burden. Current research has been aimed toward the development of a micro-CT scan and coherent-scatter analysis to determine stone composition in vivo. This may have a significant impact on the future clinical management of renal calculi by facilitating selection of the most appropriate surgical intervention based on stone composition at the time of presentation.