Emergency Doppler evaluation of the liver and kidneys

Comparison of Fenestra VC Contrast-enhanced computed tomography imaging with gadopentetate dimeglumine and ferucarbotran magnetic resonance imaging for the in vivo evaluation of murine liver damage after ischemia and reperfusion

OBJECTIVES

Comparison of intravenous Fenestra VC-enhanced computed tomography (CT) with gadopentetate dimeglumine and Ferucarbotran contrast-enhanced magnetic resonance imaging (MRI) for the in vivo imaging of hepatic ischemia/reperfusion injury (IRI) in a murine model.

MATERIAL AND METHODS

After induction of hepatic IRI by left liver lobe (LLL) ischemia (30, 45, and 75 minutes) and reperfusion (4 hours and 24 hours), a total of 130 mice were imaged either by Fenestra VC-enhanced 3-D CT or by dynamic, T1-weighed gadopentetate dimeglumine or static, T2*-weighed Ferucarbotran 2-D MRI (4.7 T).

RESULTS

Detection of liver tissue damage as a consequence of IRI was not possible by CT or MRI without the use of contrast media. (1) Mice subjected to liver IRI (45 minutes of ischemia) and injected with Fenestra VC showed a distinct liver enhancement of the viable liver tissue or a nonenhancement of the necrotic tissue. The Fenestra VC CT-unenhanced liver volume increased as a function of time of ischemia and reperfusion. The unenhanced liver volume also correlated positively with serum liver enzyme activities and damage scores from liver histology. (2) The signal intensities (SI) between normal liver tissue and livers subjected to 30 minutes of ischemia were not different on dynamic gadopentetate dimeglumine-enhanced magnetic resonance images. More severe IRI as induced by 45 or 75 minutes of ischemia was characterized by (a) early hyperenhancement of regions in the LLL with rapid increase of SI higher than that observed in the undamaged liver within the first few minutes and (b) delayed hyperenhancement in the later course after gadopentetate dimeglumine injection, respectively. (3) Ferucarbotran MRI detected signs of IRI after only 30 minutes of liver ischemia and hence detected IRI earlier than Fenestra VC or gadopentetate dimeglumine. With longer duration of ischemia, Ferucarbotran SI increased in the LLL, but viable and necrotic tissues were not clearly distinguishable.

CONCLUSIONS

MicroCT with Fenestra VC enhancement and MRI using either gadopentetate dimeglumine or Ferucarbotran enhancement of the liver revealed that all techniques allow in vivo determination of hepatic IRI as a function of the duration of ischemia and reperfusion of the liver. However, Fenestra VC-enhanced CT of the murine liver is superior to gadopentetate dimeglumine and Ferucarbotran for localization, quantification, and differentiation of viable from metabolically inactive/damaged liver tissue after hepatic ischemia/reperfusion but Fenestra VC is less sensitive than Ferucarbotran to detect the early onset of subtle consequences of hepatic IRI.

Imaging of the renal transplant: comparison of MRI with duplex sonography

Renal transplantation is an established treatment for patients with end-stage renal disease. Many causes of graft dysfunction are treatable, making prompt detection and diagnosis of complications essential. Sensitive, noninvasive imaging procedures, which do not use iodinated contrast media, are therefore highly desirable to evaluate graft function. Duplex sonography (US) has traditionally been the initial investigation of graft dysfunction. US offers many advantages, particularly during the postoperative period, when it can be performed portably regardless of renal function and can guide percutaneous procedures. However, US lacks specificity in assessing hydronephrosis, cannot differentiate parenchymal causes of dysfunction, and may have difficulty assessing transplant vessels. Recently comprehensive magnetic resonance imaging (MRI) protocols including MR urography, gadolinium-enhanced MR angiography, and MR renography have evolved as a "one-stop" diagnostic technique in the evaluation of the entire graft and peritransplant region. Multiplanar capabilities enable MRI to identify the site of urinary obstruction and assess renal vessels in their entirety. The evolving technique of MR renography may also differentiate parenchymal causes of dysfunction. By combining these three components into a single examination, further information may be obtained regarding the graft when compared with US and other conventional studies, with improved patient convenience, less morbidity, and a potential cost saving.