Short-Term Comparison of Magnetic Resonance Imaging and Spectroscopy in Persistent Canine Hepatic Encephalopathy Before and After Treatment

Objective: To compare magnetic resonance imaging (MRI) and spectroscopy (MRS) findings in dogs affected by persistent hepatic encephalopathy (HE) before and after treatment and assess any correlation between plasma ammonia levels and metabolite concentrations.
Methods: In dogs with persistent HE, plasma ammonia measurement, brain MRI and single voxel MRS were performed before and 4 months after treatment. The concentrations of N-acetyl aspartate, (NAA) glutamate-glutamine complex (Glx), creatine (Cr), choline (Cho) and myo-inositol (mI) as well as the MRI findings were
compared and the correlation with plasma ammonia concentration was evaluated. Statistical analysis included Shapiro Wilk test, Student t-test and linear-fit regression.
Results: Twenty dogs were enrolled. Initial MRI and MRS showed alterations in 18/20 and 20/20 dogs respectively. The MRI findings were normalized in dogs aged less than 3 years. Comparing post-treatment metabolite concentrations with the control group, no statistically significant differences were evident for dogs aged less than 3 years, whereas dogs aged more than 5 years showed a persistent but not significant reduction in NAA and mI, with a statistically significant increase in Glx. In dogs younger than 3 years, but not in dogs older than 5 years, a positive correlation was detected between plasma ammonia levels and Glx (r=0.80, p=0.041) and a negative correlation between ammonia level and NAA (r=-0.96, p=0.03) and between NAA and Glx (r=-0.87, p=0.037). No correlation was observed for Cr, Cho and mI.
Conclusion: In young dogs MRI and MRS findings of persistent HE can normalize after effective treatment whereas abnormalities are still detected in older dogs. MRI and MRS could therefore be useful in the short-term treatment response evaluation of persistent canine HE.