Chronic Kidney Disease (CKD)

Introduction to CKD for MCCQE1

Chronic Kidney Disease (CKD) is a progressive condition characterized by structural or functional abnormalities of the kidney. For the MCCQE1, understanding CKD is critical not only as a distinct entity but also due to its interplay with diabetes, hypertension, and cardiovascular health.

In the Canadian context, CKD is a major public health concern. According to the Kidney Foundation of Canada, 1 in 10 Canadians has kidney disease. Indigenous peoples in Canada are disproportionately affected, facing a 2 to 4 times higher risk of end-stage kidney disease (ESKD) compared to the general population—a key epidemiological fact for the exam.

Etiology and Risk Factors

Understanding the etiology is vital for the “Health Promotion and Illness Prevention” objective of the MCCQE1.

Risk Factors

• Modifiable: Hypertension, Diabetes, Smoking, Obesity, frequent NSAID use.
• Non-modifiable: Age (>60), Family history, Indigenous ancestry, South Asian or African/Caribbean background.

Pathophysiology and Staging

The KDIGO (Kidney Disease: Improving Global Outcomes) guidelines are the standard used in Canada. Staging is based on GFR and Albuminuria (CGA Staging).

GFR Categories (G Stages)

Albuminuria Categories (A Stages)

Clinical Presentation

CKD is often called a “silent disease.”

• Early Stages (G1-G3): Usually asymptomatic. Detected via screening (Serum Creatinine, Urinalysis).
• Advanced Stages (G4-G5): Symptoms of Uremia.

Uremic Symptoms (A-E-I-O-U)

• Acidosis (Metabolic)
• Electrolytes (Hyperkalemia)
• Intoxication (Mental status changes, uremic frost, pruritus)
• Overload (Fluid: edema, dyspnea)
• Uremia (Nausea, vomiting, anorexia, pericarditis, platelet dysfunction)

Diagnosis and Screening

Screening is targeted at high-risk populations (e.g., Diabetes, HTN, Indigenous peoples, family history).

Diagnostic Criteria

1. Markers of Kidney Damage (≥1 of the following):
   • Albuminuria (ACR ≥3 mg/mmol)
   • Urine sediment abnormalities (hematuria, casts)
   • Electrolyte abnormalities due to tubular disorders
   • Histological abnormalities (biopsy)
   • Structural abnormalities (imaging)
   • History of kidney transplantation
2. Decreased GFR:
   • GFR <60 mL/min/1.73 m²

These must persist for >3 months to diagnose CKD.

Management: A Canadian Approach

Management focuses on treating the underlying cause, slowing progression, and managing complications.

Management of Complications

Sick Day Management (SADMANS)

This is a high-yield concept for Canadian practice and the MCCQE1. Patients must be educated to hold certain medications during acute illness (dehydration, vomiting, diarrhea) to prevent Acute Kidney Injury (AKI).

Referral Criteria (When to consult Nephrology)

Based on Canadian guidelines, refer if:

1. Acute Kidney Injury or abrupt sustained fall in GFR.
2. GFR <30 mL/min/1.73 m² (Stage G4/G5).
3. Significant Albuminuria (ACR >60 mg/mmol or ACR >30 with hematuria).
4. Rapid Progression (GFR loss >5 mL/min/year).
5. Resistant Hypertension (≥3 drugs).
6. Red Casts or suspicion of Glomerulonephritis.

Key Points to Remember for MCCQE1

• Definition: CKD requires structural or functional damage for >3 months. One isolated low GFR is NOT CKD.
• Best Test: ACR (Albumin-to-Creatinine Ratio) is the preferred screening test for proteinuria, not dipstick.
• First Line Meds: ACEi/ARBs are renoprotective for proteinuric CKD but monitor for Hyperkalemia and Creatinine spikes.
• SGLT2 Inhibitors: Know that these are now standard of care for CKD + HF or CKD + T2DM.
• Contrast: Avoid gadolinium in GFR <30 (Risk of Nephrogenic Systemic Fibrosis).
• Indigenous Health: Be aware of the higher prevalence and the need for culturally safe care.

Sample Question

Clinical Scenario

A 68-year-old male presents to his family physician for a routine follow-up. He has a history of Type 2 Diabetes Mellitus (diagnosed 15 years ago) and Hypertension. His current medications include Metformin, Ramipril, and Amlodipine. He feels well and has no specific complaints. His blood pressure today is 134/82 mmHg.

Routine laboratory investigations reveal:

• Creatinine: 145 µmol/L (Baseline 1 year ago: 110 µmol/L)
• eGFR: 42 mL/min/1.73 m²
• Potassium: 4.8 mmol/L
• HbA1c: 7.2%
• Urine Albumin-to-Creatinine Ratio (ACR): 15 mg/mmol

A previous urinalysis 6 months ago showed trace protein but was otherwise normal.

Question

Which one of the following is the most appropriate next step in the management of this patient?

• A. Immediately refer to a nephrologist
• B. Discontinue Ramipril
• C. Repeat serum creatinine and urine ACR in 3 months
• D. Initiate renal replacement therapy education
• E. Order a renal ultrasound to rule out obstruction

Explanation

The correct answer is:

• E. Order a renal ultrasound to rule out obstruction

Detailed Explanation:

• A. Immediately refer to a nephrologist: While referral is necessary for advanced or rapidly progressive disease, Canadian guidelines generally suggest referral when eGFR is <30 mL/min/1.73 m², or if there is rapid progression or significant albuminuria (ACR >60). His GFR is 42 (Stage G3b), and while it has declined, ruling out reversible causes (like obstruction in an older male) is a primary care responsibility before referral.
• B. Discontinue Ramipril: This is incorrect. ACE inhibitors (Ramipril) are indicated for renoprotection in diabetic kidney disease with albuminuria. His potassium is normal (4.8), and there is no evidence of acute kidney injury requiring cessation.
• C. Repeat serum creatinine and urine ACR in 3 months: While confirming chronicity is part of the definition of CKD, this patient has had a significant change in baseline (Cr 110 $\rightarrow$ 145) over a year. Simply waiting 3 months without investigating the cause of the decline (e.g., obstruction, structural issues) is inappropriate “clinical inertia.”
• D. Initiate renal replacement therapy education: This is premature. Dialysis planning typically begins when GFR drops below 20-15 mL/min/1.73 m² (Stage G4/G5).
• E. Order a renal ultrasound: Correct. In an older male with a decline in GFR, it is essential to rule out post-renal causes such as obstructive uropathy (e.g., from Benign Prostatic Hyperplasia). This is a standard part of the workup for new or worsening renal dysfunction to identify reversible causes.

References

1. Kidney Disease: Improving Global Outcomes (KDIGO). CKD Evaluation and Management Guidelines.
2. Diabetes Canada Clinical Practice Guidelines Expert Committee. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada. Can J Diabetes. 2018.
3. Rabi DM, et al. Hypertension Canada’s 2020 Comprehensive Guidelines for the Prevention, Diagnosis, Risk Assessment, and Treatment of Hypertension in Adults and Children. Can J Cardiol. 2020.
4. Kidney Foundation of Canada. Facts and Stats. Available at kidney.ca.
5. Medical Council of Canada. MCCQE Part I Objectives: Renal.