Body composition in liver cirrhosis

Abstract

Patients with liver injury resulting in cirrhosis exhibit marked derangements in body composition. This is not surprising given the central role played by the liver in substrate metabolism. Progressive loss of muscle mass accompanies worsening liver disease and in end-stage disease patients typically appear wasted in the extremities with a distended abdomen due to ascites and peripheral edema. The ascites and edema in cirrhotic patients masks the profound weight loss that would otherwise occur. For this reason, malnutrition in these patients is often underdiagnosed and the widely used 2-compartment model which partitions the body into a fat compartment and a fat-free compartment is inadequate for characterizing the important features of their body composition. Measurements of body protein stores using neutron activation analysis in a large group of cirrhotics of diverse etiology highlighted the extent of malnutrition in these patients. Significant malnutrition was evident even in patients with well compensated cirrhosis and malnutrition worsened with the severity of liver disease. Protein depletion was more severe in males compared to females irrespective of disease severity. Measurement of cellular mass of the body based on assessment of total body potassium confirmed the marked depletion of muscle mass in cirrhotic patients. Fat mass depletion was shown to increase with severity of disease and to be more marked in females than males. Total body water, expressed as a fraction of the fat-free mass, was significantly elevated, with 45% of Child's A and 80% of Child's C patients falling outside the normal reference range. Overhydration of the fat-free mass was often present in patients with no clinical evidence of fluid retention. Cirrhosis was associated with loss of bone mineral and reduced bone mineral density. There is some evidence suggesting that malnutrition may underlie the pathophysiology of bone loss in these patients. Body composition assessment which provides detailed information on body compartments that is not confounded by fluid retention is essential to understanding the extent of compositional derangement that occurs in the cirrhotic patient.