Chronic kidney disease (CKD) that results in end-stage renal disease (ESRD) is a major international health problem. Many clinical markers such as urine protein or eGFR(evaluated glomerular filtration rate),can estimate the renal function, but not sensitive. As well-known, the crucial role of angiotensin II (AngII), the major effector of the renin-angiotensin system (RAS), in the development of renal fibrosis that results in ESRD is widely recognized.Abundant researches find that intrarenal RAS takes an important role on the progression of CKD. At present, no clinical marker is available to evaluate intrarenal AngII activity because it is difficult to measure it directly in patients. So find and establish a bio-marker of local renal RAS activation maybe a breakthrough in early detection and treatment of CKD. Angiotensinogen(AGT) is the only known substrate for renin and the level of AGT in humans is close to Km value for renin. Thus , changes in AGT levels can control the activity of the RAS, and its up-regulation may lead to activity of Ang levels. Then we hypothesis that the AGT is a early bio-marker of local renal RAS activation as well as CKD.

1. Screening: Select CKD(3-4) patients from outpatients, Urine routine examination and Renal B-mode ultrasonography and so on.
2. Confirm: Sign consent with the patients who meet the inclusion criteria, then these patients are included in the study.
3. Create patients records and complete related-inspections.
4. Clinical follow-up: Follow-up once every six months, and we will record every patient's disease progress every time. Each follow-up, the patient needs to leave 5 ml blood samples and 20 ml of urine samples, used for the following study.
5. Detection, Observation and Evaluation: Patients are divided into two groups according to AGT levels: higher than the normal group and the normal group. Observe the changes in eGFR of different group. Statistics judge whether AGT can be as a early warning indicators of renal function decline.

Inclusion Criteria:

• CKD, in the stage of 3 or 4, and kidney biopsy is preferred selection;
• Signed the informed consent;

Exclusion Criteria:

• Kidney cancer patients;
• Kidney transplantation;
• Hereditary kidney disease;
• Secondary renal disease(diabetic nephropathy and hypertensive nephropathy are excluded)

CKD（chronic kidney disease），in the stage of 3 or 4.