IMAGING

doi: 10.1590/S1677-55382010000400019

Kidney and urinary tract imaging: triple-bolus multidetector CT urography as a one-stop shop--protocol design, opacification, and image quality analysis
Kekelidze M, Dwarkasing RS, Dijkshoorn ML, Sikorska K, Verhagen PC, Krestin GP
Department of Radiology, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands
Radiology. 2010; 255: 508-16

• Purpose: To retrospectively evaluate renal, vascular, and urinary tract visualization following a single postcontrast multidetector computed tomographic (CT) urographic sequence performed with three limited-volume bolus injections.
  Materials and Methods: The institutional review board approved this retrospective study. Patient informed consent was waived. Triple-bolus multidetector CT urography was performed in 110 patients. Triple-bolus protocol consisted of 30 mL of contrast material at 2 mL/sec at 0 seconds, 50 mL at 1.5 mL/sec at 435 seconds, 65 mL at 3 mL/sec at 488 seconds, with total abdominal scanning time of 510 seconds. Two independent readers rated urinary tract opacification and qualitatively and quantitatively assessed renal parenchymal and vascular contrast enhancement. Upper urinary tract (UUT) distention was measured by one reader. Interobserver agreement was assessed by using kappa statistics.
  Results: Complete opacification of the intrarenal collecting system and proximal ureter was achieved in 91% (184 of 202) (kappa = 0.62) and 82% (166 of 202) (kappa = 0.94) of segments, respectively. The distal ureter was not opacified in 21% of the cases (kappa = 0.92), and the bladder was not opacified in 20% of the cases. Mean distention was higher for proximal (3.9 mm) than for distal (3.7 mm) segments. Image quality of renal parenchymal enhancement was excellent in 76% of cases. Arteries showed better contrast enhancement than veins (excellent rating in 89% vs 59% of the cases). Radiation dose calculated for triple-bolus acquisition was 9.8 mSv.
  Conclusion: Triple-bolus multidetector CT urography is a dose-efficient protocol acquiring corticomedullary-nephrographic-excretory and vascular enhancement phases in a single acquisition and provides sufficient opacification and distention of the UUT. Simultaneously, adequate image quality of renal parenchyma and vascular anatomy is achieved.

• Editorial Comment
  Multidetector computed tomography urography (MDCTU) has become the method of choice for investigation patients with hematuria. For the adequate characterization of parenchymal, urothelial or vascular abnormalities a three-phase MDCT urographic protocols is usually necessary. With this protocol, following an unenhanced phase a single-bolus contrast material injection is made and nephrographic, and excretory phases are obtained. Using this three-phase protocol the effective radiation dose to the patient range from 15-18 mSv. If visualization of the renal arteries and branches are necessary, an additional arterial phase is obtained, thus increasing the radiation dose to 18-20 mSV. For this reason radiologist should always perform a tailored MDCT-urography protocol adequate for each patient clinical indication. The authors’ presents a triple-bolus protocol designed to show all renal contrast-enhancement phases in a single acquisition. Good results were obtained with this technique, which allows the demonstration of the renal parenchyma, the renal arteries and veins and all portions of urinary tract. After an enhanced phase, a single postcontrast MDCT urographic sequence is performed with three limited-volume bolus injections. The first bolus of intravenous contrast material is for the opacification of the urinary tract, the second bolus is for the opacification of the venous system and the last bolus is performed for the opacification of the arterial system. We have found that this protocol is excellent for evaluation of potential renal donors, a characteristic group of healthy and young patients that are benefited with the use of a low-dose protocol (11-13 mSv).

Dr. Adilson Prando
Head, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com