Chronic kidney disease is a common global public health issue and its prevalence increased year by year. Early diagnosis and intervention can prevent further complications and comorbidities of long-term dialysis, cardiovascular events and mortality as well as improve the patients' life quality. To differentiate acute from chronic kidney disease was crucial especially in the setting of crowded and high-risk emergency department. To diagnose acute or chronic kidney disease, physicians usually use blood sample test combined with image studies such as conventional sonography, CT and MRI. However, there was lots of limited factors. The patients may have no previous visit records, poor renal function to receive contrast medium, or critical clinical condition to undergo time-wasting exam. Although the conventional renal sonography is accessible and inexpensive, the judgement is subjective and provide little clinical information. Recent researches of shear wave elastography in evaluating renal parenchymal stiffness showed some correlation with nephropathy. In our study, aiming to facilitating clinical implication, the investigators will use swear-wave elastography combined with conventional renal sonography to benefit patients in diagnosis of acute or chronic kidney disease.

This is a case-control study. The investigators obtained data from participants who were older than 20 years old and received renal sonography examination in the emergency department of National Taiwan University Hospital. The investigators examined the participants' kidneys by recording the kidney size, cortical thickness, possible lesions and elasticity by shear-wave elastography. These data combined with the participants' medical history and renal function revealed by blood examination will be analyzed. This study was designed to determine the correlation between renal cortical elasticity and chronic kidney disease.

Inclusion Criteria:

• The patients older than 20 years old who needed to receive renal sonography in emergency department of National Taiwan University Hospital.

Exclusion Criteria:

• The patients who didn't obtain agreement.
• The patients who can't cooperate or follow the directions

Approximately 400 patients with normal kidney function and 400 patients with abnormal kidney function