Study of Urinary Angiotensinogen as a Marker to Warn the Deterioration of Renal Function in CKD Patients Early.

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.