Objective To explore the possibility of quantitatively evaluating muscle volume loss and fatty infiltration in viral cirrhotic patients by conventional upper abdominal magnetic resonance(MR)four-phase images.Methods The skeletal muscles of lower back,including psoas major,quadratus lumborum,erector spinae and multifidus muscle,were measured at the third lumbar vertebra(L3)plane on MR images of young adult volunteers and viral cirrhotic patients.And then,the modified skeletal muscle index(mSMI)and modified fat fraction(mFF)were calculated.The muscle volume loss and fatty infiltration in viral cirrhotic patients were judged by mSMI and mFF,respectively,with the data of the young adult volunteers used as refer-ence.The number difference between the patients with muscle volume loss and with fatty infiltration was compared by Chi-square test.Binary Logistic regression analysis was used to assess whether gender,age,the course of chronic viral hepatitis were factors on mSMI or mFF.Results Totally,sixty volunteers and 182 viral cirrhotic patients were enrolled.Among cirrhotic patients,16(8.8%)got muscle loss assessed by mSMI,while 76(41.8%)got fatty infiltration assessed by mFF,with statistical significance(x2=52.4,P<0.01).Binary Logistic regression analysis showed that age(P<0.01),gender(P<0.01),the course of viral hepatitis cirrhosis(P=0.01)were factors for mSMI.And age(P<0.01)and the course of viral hepatitis cirrhosis(P<0.05)were factors for mFF,while gender(P>0.05)was not factor for mFF.Conclusion Conventional upper abdominal MRI may be used to detect muscle loss in patients with liver cirrhosis.mFF is more sensitive to detect muscle changes than mSMI.mFF is affected by age and the course of viral hepatitis cirrhosis,while mSMI is affected by age,gender and the course of viral hepatitis cirrhosis.