Usefulness of chemical-shift MRI in discriminating increased liver echogenicity in glycogenosis

BACKGROUND: Glycogen storage diseases are inherited defects which cause accumulation of glycogen in the tissues. Hepatic steatosis is defined as accumulation of fat within hepatocytes. On sonography, liver shows increased echogenicity both in glycogen storage diseases and steatosis. Liver hyperechogenicity in glycogen storage diseases may depend on accumulation of glycogen and/or fat. Chemical-shift magnetic resonance imaging can discriminate tissues only containing water from those containing both fat and water. AIM: The primary aim of the present study was to evaluate the usefulness of liver chemical-shift magnetic resonance imaging for detecting liver steatosis in patients with metabolic impairment due to glycogen storage diseases. SUBJECTS: Twelve patients with type I (n=8) or type III (n=4) glycogen storage diseases were studied and compared to 12 obese-overweight subjects with known liver steatosis. As control group 12 lean normal voluntary subjects were recruited. METHODS: Liver was evaluated by sonography and chemical-shift magnetic resonance imaging to calculate hepatic fat fraction. RESULTS: A significant difference in echogenicity between patients with glycogen storage diseases and normal subjects was observed (p<0.05), while this difference was not present between overweight-obese and glycogen storage diseases patients. On the contrary, fat fraction was similar between glycogen storage diseases patients and normal subjects and different between glycogen storage diseases patients and overweight-obese (p<0.05). CONCLUSION: The present data suggest that chemical-shift magnetic resonance imaging may exclude fat deposition as a cause of liver hyperechogenicity in subjects with glycogen storage diseases