 Malnutrition is a major risk factor for morbidity and mortality of patients managed in intensive care unit. Early recognition and treatment of adult malnutrition are recommended in acute care settings especially for patients requiring mechanical ventilation. Biochemical indicators like serum concentrations of albumin and prealbumin transthyretin have a tradition of being used as markers of nutritional status but remains influenced by nonnutritional factors. A recent assessment of quadriceps muscle diameter with ultrasound method has gained interest for screening and follow-up of muscle weakness at the bedside in critically ill patients. The purpose of the study is to investigate the validity of ultrasound as measurement tool for assessing malnutrition acquired in intensive care unit. 