title: Novel equation to determine the hepatic triglyceride concentration in humans by MRI: diagnosis and monitoring of NAFLD in obese patients before and after bariatric surgery.
abstract: BACKGROUND
  Non-alcoholic fatty liver disease (NAFLD) is caused by abnormal accumulation of lipids within liver cells. Its prevalence is increasing in developed countries in association with obesity, and it represents a risk factor for non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Since NAFLD is usually asymptomatic at diagnosis, new non-invasive approaches are needed to determine the hepatic lipid content in terms of diagnosis, treatment and control of disease progression. Here, we investigated the potential of magnetic resonance imaging (MRI) to quantitate and monitor the hepatic triglyceride concentration in humans.
  
  
  METHODS
  A prospective study of diagnostic accuracy was conducted among 129 consecutive adult patients (97 obesity and 32 non-obese) to compare multi-echo MRI fat fraction, grade of steatosis estimated by histopathology, and biochemical measurement of hepatic triglyceride concentration (that is, Folch value).
  
  
  RESULTS
  MRI fat fraction positively correlates with the grade of steatosis estimated on a 0 to 3 scale by histopathology. However, this correlation value was stronger when MRI fat fraction was linked to the Folch value, resulting in a novel equation to predict the hepatic triglyceride concentration (mg of triglycerides/g of liver tissue = 5.082 + (432.104 * multi-echo MRI fat fraction)). Validation of this formula in 31 additional patients (24 obese and 7 controls) resulted in robust correlation between the measured and estimated Folch values. Multivariate analysis showed that none of the variables investigated improves the Folch prediction capacity of the equation. Obese patients show increased steatosis compared to controls using MRI fat fraction and Folch value. Bariatric surgery improved MRI fat fraction values and the Folch value estimated in obese patients one year after surgery.
  
  
  CONCLUSIONS
  Multi-echo MRI is an accurate approach to determine the hepatic lipid concentration by using our novel equation, representing an economic non-invasive method to diagnose and monitor steatosis in humans.
authors.forename: Raúl
authors.initials: R
authors.lastname: Jiménez-Agüero
authors.forename: José I
authors.initials: JI
authors.lastname: Emparanza
authors.forename: Adolfo
authors.initials: A
authors.lastname: Beguiristain
authors.forename: Luis
authors.initials: L
authors.lastname: Bujanda
authors.forename: José M
authors.initials: JM
authors.lastname: Alustiza
authors.forename: Elisabeth
authors.initials: E
authors.lastname: García
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hijona
authors.forename: Lander
authors.initials: L
authors.lastname: Gallego
authors.forename: Javier
authors.initials: J
authors.lastname: Sánchez-González
authors.forename: María J
authors.initials: MJ
authors.lastname: Perugorria
authors.forename: José I
authors.initials: JI
authors.lastname: Asensio
authors.forename: Santiago
authors.initials: S
authors.lastname: Larburu
authors.forename: Maddi
authors.initials: M
authors.lastname: Garmendia
authors.forename: Mikel
authors.initials: M
authors.lastname: Larzabal
authors.forename: María P
authors.initials: MP
authors.lastname: Portillo
authors.forename: Leixuri
authors.initials: L
authors.lastname: Aguirre
authors.affiliation: Department of Liver and Gastrointestinal Diseases, Biodonostia Research Institute, Donostia University Hospital (HUD), University of the Basque Country (UPV/EHU), San Sebastian, Spain. jesus.banales@biodonostia.org.
authors.forename: Jesús M
authors.initials: JM
authors.lastname: Banales
mesh_terms: D050110:Bariatric Surgery; D003430:Cross-Sectional Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease / Q000473:pathology*; D009765:Obesity; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012720:Severity of Illness Index; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D014280:Triglycerides