Multidetector CT urography-When, Why, How?

Škugor J, MD, radiologist, Zorić-Burić V, MD, radiologist, Paić M, MD, urologist, Reljić D, MD, urologist

General Hospital Šibenik

CT urography (CTU) is a single examination that allows evaluation of potential urinary tract calculi, renal parenhymal masses and both benign and malignant urothelial masses with the highest sensitivity and specificity for detection of pathology.

Bowel gas, a frequent visual barrier in excretory urography (EU) interpretation is not an issue in CT urography. In addition, pathology with extrinsic mass effect on the collecting system, such as anomalous crossing renal vessels or aneurysms, can be confidently diagnosed. The 3D rendering (SSD, VRT, MIP) of the urinary tract permits visualization in multiple planes. Clinicians are presented with coronal images of the collecting system similar to the traditional EU.

Tumors of renal korteks and collecting system can be detected more easily on CTU then on EU. When a tumor is identified, staging is accomplished simuntaneusly, sparing the patient added studies, traditional EU would necessiate CT or MR to confirm cystic vrs solid lesion, evaluate local invasion and distant metastasis, vascular extension and lymph node involvement.

There are many different techniques, the one we mostly use is split-bolus tehnique with administration of fursemide, that combine nephrographic and excretory phase into a single phase with a significant reduction in the patient’s radiation dose when compared to the standard threephasic scanning protocol of examination.

The CTU has been proven as a „one stop shop“imaging modality that offers the complete analysis of the urinary tract in the course of only one examination but with a relatively high radiation dose when compared to the conventional EU and because of that this metode necessiate maintaining the reasonable indication range, using fewer scanning phases during examination and applying different imaging protocols suited for particular indications in order to lowering radiation risk and radiation doses to the patients.