Chapter 11: Chronic Kidney Disease (CKD)

Definition and Staging

Chronic kidney disease is defined as abnormalities of kidney structure or function present for more than 3 months, with implications for health. The staging system combines GFR categories with albuminuria categories to provide a comprehensive risk assessment for progression and complications.

CKD Risk Stratification Matrix

The following table from KDIGO guidelines shows the risk of progression based on GFR category and albuminuria level, guiding monitoring frequency and treatment intensity:

GFR Category (mL/min/1.73m²)	Albuminuria Category (mg/g)
GFR Category (mL/min/1.73m²)	G1 (≥90)	Low Risk*	Moderate Risk	High Risk
G2 (60-89)	Low Risk*	Moderate Risk	High Risk
G3a (45-59)	Moderate Risk	High Risk	Very High Risk
G3b (30-44)	High Risk	Very High Risk	Very High Risk
G4 (15-29)	Very High Risk	Very High Risk	Very High Risk
G5 (<15)	Very High Risk	Very High Risk	Very High Risk

*Note: G1 and G2 categories require evidence of kidney damage (e.g., albuminuria, hematuria, structural abnormalities) for a CKD diagnosis.

Common Causes of CKD

Diabetes Mellitus (45% of cases): The leading cause in developed countries.
Hypertension (25% of cases): Both a cause and a consequence of CKD.
Glomerular Diseases (15% of cases): Including primary glomerulonephritis and lupus nephritis.
Polycystic Kidney Disease (5% of cases): The most common inherited cause.

Management Strategies to Slow Progression

The Pillars of CKD Management

Blood Pressure Control: Target <130/80 mmHg.
RAAS Inhibition: Use of ACE inhibitors or ARBs, especially with albuminuria.
SGLT2 Inhibition: Now a cornerstone therapy for many with CKD, with or without diabetes.
Glycemic Control: In diabetic patients, target HbA1c <7%.
Lifestyle Modifications: Including sodium restriction, healthy diet, and smoking cessation.

Complications of CKD

Anemia of CKD

Typically develops when eGFR falls below 30 mL/min/1.73m² due to decreased erythropoietin production. Before starting erythropoiesis-stimulating agents (ESAs), iron stores must be replete (Ferritin >100 ng/mL, TSAT >20%). The target hemoglobin is 10-11 g/dL.

Mineral and Bone Disorder (CKD-MBD)

A complex syndrome of disordered mineral metabolism (calcium, phosphorus, PTH, vitamin D) leading to bone disease (renal osteodystrophy) and vascular calcification. Management involves dietary phosphorus restriction, phosphate binders, and vitamin D analogs.

Metabolic Acidosis

Develops due to the kidneys' decreased ability to excrete the daily acid load. Chronic metabolic acidosis contributes to muscle wasting and bone disease. Treatment with oral sodium bicarbonate to maintain a serum bicarbonate level >22 mEq/L may slow CKD progression.

Preparation for Renal Replacement Therapy (RRT)

Patient education and preparation for RRT should begin when the eGFR approaches 30 mL/min/1.73m² (Stage G4). This allows adequate time for modality selection (hemodialysis, peritoneal dialysis, transplantation) and, crucially, for the creation and maturation of vascular access for hemodialysis, which can take several months.

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