ESSENTIALS OF DIAGNOSIS
Abnormally elevated serum creatinine for more than 3 months
Calculated glomerular filtration rate (GFR) less than 60 mL/min/1.73 m2 for more than 3 months
Clinical manifestations of the uremic syndrome in patients with advanced kidney failure
The Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (CKD) has defined CKD as abnormalities of kidney structure or function, present for more than 3 months, with implications for health. Structural or functional abnormalities may manifest by markers of kidney damage and/or glomerular filtration rate (GFR) less than 60 mL/min/1.73 m2 of body surface area. Markers of kidney damage include albuminuria greater than or equal to 30 mg/24 h (or ≥30 mg/g by albumin/creatinine ratio), urine sediment abnormalities (ie, microscopic hematuria), electrolyte and other abnormalities due to tubular disorders (ie, renal tubular acidosis), abnormalities detected by histology (ie, chronic glomerulonephritis) or imaging studies (ie, polycystic kidneys), or history of kidney transplantation. GFR can be estimated from serum creatinine or cystatin C with a formula, preferably the chronic kidney disease-epidemiology collaboration (CKD-EPI) equation. Persistence of abnormalities for more than 3 months is important to distinguish between acute and chronic kidney disease, and has implications for health to exclude benign conditions (ie, a simple renal cyst is a structural abnormality of the kidney but with minimal health risks for the individual).
According to KDIGO, CKD can be classified based on the level of GFR (G1–G5), the degree of albuminuria (A1–A3), and the likely cause of CKD (Table 18–1). Whereas the definition of CKD stages G3–G5 is solely based on a level of GFR less than 60 mL/min/1.73 m2, CKD stages G1 and G2 require that the level of GFR greater than 60 mL/min/1.73 m2 be accompanied by a marker of kidney damage (typically, moderately, or severely increased albuminuria). As an example, a patient with an estimated GFR of 40 mL/min/1.73 m2, albuminuria of 380 mg/g by ACR, and likely diabetic nephropathy would be classified as G3b, A3, and diabetic nephropathy as the cause.
Table 18–1.Classification of chronic kidney disease and management recommendations.a ||Download (.pdf) Table 18–1. Classification of chronic kidney disease and management recommendations.a
|Stage ||Description (at increased risk) ||GFR (mL/min/1.73 m2) (>90 [CKD risk factors]) ||Management (screening CKD risk reduction) |
|1 ||Kidney damage with normal or ↑ GFR ||>90 ||Diagnosis and Rx CVD risk reduction |
|2 ||Mild ↓ GFR ||60–89 ||Estimating progression |
|3 ||Moderate ↓ GFR ||30–59 ||Evaluating and treating complications |
|4 ||Severe ↓ GFR ||15–29 ||Preparation for kidney replacement therapy |
|5 ||Kidney failure ||<15 or dialysis ||Replacement, if uremia is present |