Kidney damage is defined as pathological abnormalities or markers of damage, including abnormalities in blood or urine tests or imaging studies. Stage 2: Mild reduction in GFR (60–89 mL/min/1.73 m2) with kidney damage. Kidney damage is defined as pathological abnormalities or markers of damage, including abnormalities in blood or urine tests or imaging studies. Stage 3: Moderate reduction in GFR (30–59 mL/min/1.73 m2):. British guidelines distinguish between stage 3A (GFR 45–59) and stage 3B (GFR 30–44) for purposes of screening and referral. Stage 4: Severe reduction in GFR (15–29 mL/min/1.73 m2) Preparation for kidney replacement therapy. Stage 5: Established kidney failure (GFR <15 mL/min/1.73 m2), permanent kidney replacement therapy, or end-stage kidney disease.The term "non-dialysis-dependent chronic kidney disease" (NDD-CKD) is a designation used to encompass the status of those persons with an established CKD who do not yet require the life-supporting treatments for kidney failure known as kidney replacement therapy (RRT, including maintenance dialysis or kidney transplantation). The condition of individuals with CKD, who require either of the two types of kidney replacement therapy (dialysis or transplant), is referred to as the end-stage kidney disease (ESKD). Hence, the start of the ESKD is practically the irreversible conclusion of the NDD-CKD. Even though the NDD-CKD status refers to the status of persons with earlier stages of CKD (stages 1 to 4), people with advanced stage of CKD (stage 5), who have not yet started kidney replacement therapy, are also referred to as NDD-CKD.
Most agree that nephrology referral is required by Stage 4 CKD (when eGFR/1.73m2 is less than 30 mL/min; or decreasing by more than 3 mL/min/year).It may also be useful at an earlier stage (e.g. CKD3) when urine albumin-to-creatinine ratio is more than 30 mg/mmol, when blood pressure is difficult to control, or when hematuria or other findings suggest either a primarily glomerular disorder or secondary disease amenable to specific treatment. Other benefits of early nephrology referral include proper education regarding options for kidney replacement therapy as well as pre-emptive transplantation, and timely workup and placement of an arteriovenous fistula in those people with chronic kidney disease opting for future hemodialysis. Renal replacement therapy
At stage 5 CKD, kidney replacement therapy is usually required, in the form of either dialysis or a kidney transplant. In CKD numerous uremic toxins accumulate in the blood. Even when ESKD (largely synonymous with CKD5) is treated with dialysis, the toxin levels do not go back to normal as dialysis is not that efficient. Similarly, after a kidney transplant, the levels may not go back to normal as the transplanted kidney may not work 100%. If it does, the creatinine level is often normal. The toxins show various cytotoxic activities in the serum and have different molecular weights, and some of them are bound to other proteins, primarily to albumin. Uremic toxins are classified into three groups as small water-soluble solutes, middle molecular-weight solutes, and protein-bound solutes.