(CRF) Irreversible, progressive impaired kidney function. The early stage, when the kidneys no longer function properly but do not yet require dialysis, is known as Chronic Renal Insufficiency (CRI). CRI can be difficult to diagnose, as symptoms are not usually apparent until kidney disease has progressed significantly. Common symptoms include a frequent need to urinate and swelling, as well as possible anemia, fatigue, weakness, headaches and loss of appetite. As the disease progresses, other symptoms such as nausea, vomiting, bad breath and itchy skin may develop as toxic metabolites, normally filtered out of the blood by the kidneys, build up to harmful levels. Over time (up to 10 or 20 years), CRF generally progresses from CRI to End-Stage Renal Disease (ESRD, also known as Kidney Failure). Patients with ESRD no longer have kidney function adequate to sustain life and require dialysis or kidney transplantation. Without proper treatment, ESRD is fatal.