Silvia Cisneros Carpio MD, Abstract Co-Author: Nothing to Disclose

Eneritz Larrazabal MD, Presenter: Nothing to Disclose

Inigo Lecumberri MD, Abstract Co-Author: Nothing to Disclose

Jose Luis Del Cura MD, Abstract Co-Author: Nothing to Disclose

Berta Ruiz MD, Abstract Co-Author: Nothing to Disclose

Laura Alvarez De Eulate MD, Abstract Co-Author: Nothing to Disclose

Igone Corta MD, Abstract Co-Author: Nothing to Disclose

Gonzalo Lecumberri, Abstract Co-Author: Nothing to Disclose

To evaluate whether or not there exists a relation between the size of the nephrolithiasis and the lack of its detection in the VNC images obtained from the CT urography studies conducted in a dual-energy CT.

Retrospective study in which 24 consecutive patients who underwent CT urography were reviewed. All the studies were obtained using a dual-energy multidetector CT. A CT urography was conducted on all the patients with two series (non-contrast and a mixed nephrographic and pyelographic phase) with the double injection technique, which is the standard protocol we carry out in our service. The true non-contrast (TNC) images (which were used as the reference study) were analysed by a radiologist who calculated the nephrolithiasis and measured the maximum diameter of the stones in the cross-sectional plane. Subsequently, the same radiologist reviewed the virtual non-contrast (VNC) images and calculated and measured the nephrolithiasis. The nephrolithiasis identified in the VNC images were correlated with those seen in the TNC series.  

Of the 24 patients, only 8 had any nephrolithiasis, with a total of 58 stones, of which 36 (62%) were not detected in the VNC, 13 (22%) were detected but the size had decreased, 8 (14%) had increased and 1 (2%) had not varied in size. Up to 2.5 mm, all the stones disappeared in the VNC. Between 2.5 and 4.7 mm, the majority disappeared or decreased in size. There was a very low frequency of a stone > 5 mm was not detected in the VNC.  

Many of the nephrolithiasis are not detected in the VNC images and this fact occurred principally with stone under 2.5 mm.

If we do not conduct the TNC series in order to decrease the radiation to the patients and we analyze the VNC images, the small-sized renal calculi may be underdetected.

Cisneros Carpio, S, Larrazabal, E, Lecumberri, I, Del Cura, J, Ruiz, B, Alvarez De Eulate, L, Corta, I, Lecumberri, G, Detectability of Nephrolithiasis on Virtual Nonenhanced Images at Dual-Energy CT Urography.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11006119.html