---
title: Chronic Kidney Disease Staging
description: A comprehensive clinical reference on the staging and management of chronic kidney disease.
keywords: [chronic kidney disease, CKD, glomerular filtration rate, albuminuria, KDIGO]
category: clinical
---

## Definition and Epidemiology

Chronic kidney disease (CKD) is defined as abnormalities of kidney structure or function, present for more than 3 months, with implications for health [1]. CKD is classified into 5 stages based on the level of glomerular filtration rate (GFR) and presence of kidney damage, as per the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines [1]. 

The prevalence of CKD in the general adult population is estimated to be 11-13% globally [2]. Diabetes and hypertension are the leading causes, accounting for up to 70% of all CKD cases [3]. Other etiologies include glomerulonephritis, polycystic kidney disease, and obstructive uropathy. Advancing age, obesity, and cardiovascular disease are also major risk factors for CKD.

## Staging of CKD

CKD is staged according to the level of GFR and presence of kidney damage, as shown in Table 1 [1]:

Table 1. CKD Stages

| Stage | GFR (mL/min/1.73m²) | Description |
| ----- | ------------------- | ----------- |
| G1    | ≥ 90                | Normal or high GFR, with other evidence of kidney damage |
| G2    | 60-89               | Mildly decreased GFR, with other evidence of kidney damage |
| G3a   | 45-59               | Mildly to moderately decreased GFR |
| G3b   | 30-44               | Moderately to severely decreased GFR |
| G4    | 15-29               | Severely decreased GFR |
| G5    | < 15                | Kidney failure |

Kidney damage is defined by the presence of albuminuria, abnormalities in urine sediment, electrolyte and other abnormalities due to tubular disorders, or structural abnormalities detected by imaging [1]. The severity of albuminuria is classified as:
- A1: Albumin-to-creatinine ratio (ACR) < 30 mg/g
- A2: ACR 30-300 mg/g 
- A3: ACR > 300 mg/g

## Diagnosis and Evaluation

The initial evaluation of CKD includes assessment of GFR, albuminuria, and identification of the underlying etiology. GFR is estimated using serum creatinine-based equations, such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula [4]. Albuminuria is measured by the urine ACR.

Additional testing may include:
- Urinalysis to assess for hematuria, pyuria, or casts
- Imaging studies (ultrasound, CT, MRI) to evaluate kidney size, structure, and obstruction
- Serologic tests for autoimmune or metabolic disorders
- Kidney biopsy in select cases to determine the underlying cause

## Management and Treatment

The goals of CKD management are to slow disease progression, manage complications, and reduce the risk of cardiovascular events. The specific treatment approach is guided by the CKD stage, underlying etiology, and presence of comorbidities.

### Lifestyle Modifications
All patients with CKD should be advised on the following lifestyle changes:
- Dietary modifications to limit protein, sodium, potassium, and phosphorus intake
- Weight loss for overweight/obese patients
- Smoking cessation
- Regular physical activity

### Pharmacologic Therapy
Several drug classes are used in the management of CKD:
- Renin-angiotensin-aldosterone system (RAAS) inhibitors (e.g., ACE inhibitors, ARBs) to reduce proteinuria and slow disease progression
- Diuretics (e.g., loop diuretics, thiazides) to manage fluid overload and hypertension
- Phosphate binders (e.g., calcium acetate, sevelamer) to control hyperphosphatemia
- Vitamin D analogues (e.g., calcitriol) to manage secondary hyperparathyroidism
- Erythropoiesis-stimulating agents (e.g., epoetin alfa) to treat anemia

Dosing of medications may need to be adjusted based on the stage of CKD to avoid adverse effects.

### Monitoring and Referral
Patients with CKD require regular monitoring of kidney function, electrolytes, anemia, and mineral/bone disorders. Referral to a nephrologist is recommended for:
- GFR < 30 mL/min/1.73m² (CKD stages 4-5)
- Rapid decline in GFR (> 4 mL/min/1.73m² per year)
- Uncontrolled hypertension or proteinuria
- Electrolyte abnormalities
- Preparation for kidney replacement therapy

## Cardiovascular Risk Management

Patients with CKD have an increased risk of cardiovascular disease, which is the leading cause of morbidity and mortality in this population. Comprehensive cardiovascular risk management is crucial and includes:
- Strict blood pressure control (target < 130/80 mmHg)
- Lipid management with statins
- Antiplatelet therapy (aspirin) for those with established cardiovascular disease
- Glycemic control in patients with diabetes
- Lifestyle modifications (diet, exercise, smoking cessation)

## Progression to Kidney Failure and Renal Replacement Therapy

Patients with CKD stage 5 (GFR < 15 mL/min/1.73m²) are considered to have kidney failure and require renal replacement therapy, which includes dialysis (hemodialysis or peritoneal dialysis) or kidney transplantation. Timely referral to a nephrologist is essential to prepare patients for this transition and ensure optimal outcomes.

## Conclusion

Chronic kidney disease is a common and progressive condition that requires a multifaceted approach to management. Accurate staging based on GFR and albuminuria, along with identification and treatment of the underlying cause, are key to slowing disease progression and reducing the risk of complications. Close monitoring and timely referral to a nephrologist are essential for patients with advanced CKD.

## References

1. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. 2013;3(1):1-150.
2. Hill NR, Fatoba ST, Oke JL, et al. Global Prevalence of Chronic Kidney Disease - A Systematic Review and Meta-Analysis. PLoS One. 2016;11(7):e0158765.
3. Coresh J, Selvin E, Stevens LA, et al. Prevalence of chronic kidney disease in the United States. JAMA. 2007;298(17):2038-2047.
4. Levey AS, Stevens LA, Schmid CH, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604-612.