The goal of this observational study is to evaluate whether thigh muscle mass and muscle wasting are associated with mortality in patients who visit the emergency department. The main questions it aims to answer are:

• Is thigh muscle mass associated with mortality in patient who visit the emergency department?
• Does muscle wasting exist during staying in the emergency department?
• Is muscle wasting associated with mortality in patient who visit the emergency department? Participants will be evaluated for serial thigh muscle mass using point-of-care ultrasound at the emergency department.

Inclusion Criteria:

• patients who visit the emergency department of Korea University Ansan Hospital during study period
• patients with age within the limits
• patients who are willing to be participate the study with informed consent
• patients who undergo point-of-care ultrasound to evaluate thigh muscle mass

Exclusion Criteria:

• patients with age out of limits
• patients who have deformities on lower leg
• patients who is unable to maintain appropriate position to undergo point-of-care ultrasound
• patients who decline to participate the study
• patients who have 'do-not-resuscitate' order or are not willing to be resuscitated
• patients of whom point-of-care ultrasound on thigh muscle mass was not performed

Patients who visit the emergency department with informed consent and then who undergo point-of-care ultrasound to evaluate thigh muscle mass.