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In vivo proton magnetic resonance spectroscopy for the evaluation of hepatic encephalopathy in dogs

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  • 1 Division of Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 2 Division of Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 3 MR Zentrum USZ, Institute for Biomedical Engineering, University and ETH (Swiss Federal Institute of Technology) Zurich, 8092 Zurich, Switzerland.
  • | 4 Division of Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 5 Division of Neurology, Clinic for Small Animal Surgery, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.
  • | 6 Division of Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, 8057 Zurich, Switzerland.

Abstract

Objective—To investigate clinical use of proton magnetic resonance spectroscopy (1H MRS) and to compare metabolic brain bioprofiles of dogs with and without hepatic encephalopathy.

Animals—6 dogs with hepatic encephalopathy and 12 control dogs.

Procedures—Conventional MRI and single-voxel 1H MRS were performed with a 3-T magnet. Images for routine MRI planes and sequences were obtained. Single-voxel 1H MRS was performed with a point-resolved sequence with a short echo time (35 milliseconds) and voxel of interest placement at the level of the basal ganglia. Metabolites of interest included the glutamine-glutamate complex (sum quantification of glutamate and glutamine), myoinositol, N-acetyl aspartate, total choline, and creatine. Data were analyzed with postprocessing fitting algorithm software, and metabolite concentration relative to water and ratios with creatine as the reference metabolite were calculated.

Results—Compared with control dogs, dogs with hepatic encephalopathy had specific changes, which included significantly higher concentration relative to water of the glutamine-glutamate complex and significantly lower concentration of myoinositol. Choline and N-acetyl aspartate concentrations were also slightly lower in dogs with hepatic encephalopathy than in control dogs. No differences in creatine concentration were detected between groups.

Conclusions and Clinical Relevance1H MRS aided in the diagnosis of hepatic encephalopathy in dogs, and findings supported the assumption that ammonia is a neurotoxin that manifests via glutamine-glutamate complex derangements. Use of 1H MRS may provide clinically relevant information in patients with subclinical hepatic encephalopathy, equivocal results of bile acids tests, and equivocal ammonia concentrations or may be helpful in monitoring efficacy of medical management.

Contributor Notes

This manuscript represents a portion of a thesis submitted by Dr. Carrera to the Graduate School for Cellular and Biomedical Sciences, Bern University, Bern, Switzerland, as a partial fulfillment of the requirements for a PhD degree.

The authors thank Dr. Ronald Kreis and Dr. Chris Boesch for technical assistance.

Address correspondence to Dr. Carrera (icarrera@vetclinics.uzh.ch).