4. Chronic kidney disease: drug therapy

Question 1

What is the definition of CKD?

Answer 1

Impaired renal function for >3months based on abnormal structure or function (GFR < 60ml/min)

Question 2

What is the classification of CKD?

Answer 2

• CKD is classified into 5 stages based on the GFR and presence of renal damage (proteinuria, hematuria, sediment, abnormal anatomy or evidence of a systemic disease)
• Symptoms usually only occure by stage 4 (GFR < 30ml/min)
• End-stage renal disease (ESRD) is defined as GFR < 15ml/min or need of renal replacement therapy (RRT)

Question 3

What are the causes of CKD? Rare causes? Inherited diseases?

Answer 3

• Diabetes mellitus
• Glomerulonephritis
  
  • Commonly IgA nephropathy
  • Systemic disorders (SLE, vasculites)
• HTN or renovascular disease
• Pyelonephritis and reflux nephropathy
• Unknown (at the time of patient arrival biopsyis no longer diagnostic)

Rare causes:

• Obstructive uropathy: commonly causes AKI (often reversible)
• Chronic interstitial nephritis (myeloma, amyloidosis)
• Following previous AKI

Inherited diseases:

• Adult PKD (most common inherited cause)
• Alport’s syndrome and Fabry’s diseases are rare

Question 4

What is the management of CKD?

Answer 4

Refer early to a nephrologist if any of the criteria:

• Stage 4-5 CKD
• Moderate proteinuria (ACR > 70mg/mmol) unless due to DM and already appropriately treated
• Proteinuria + hematuria
• Rapidly falling eGFR (>5ml/min within a year or >10ml/min within 5 years)
• Poorly controlled BP despite ≥ 4 antihypertensive drugs at therapeutic doses
• Known or suspected rare genetic causes of CKD
• Suspect renal artery stenosis

Question 5

What is the aim of management of CKD?

Answer 5

Limiting the progression of the disease, minimizing the risk for complications and handling these complications when they arise.

Question 6

How can we identify and treat the reversible causes?

Answer 6

• Relieve obstruction
• Stop nephrotoxicity drugs
• Deal with hypercalcemia
• Deal with cardiovascular risks (stop smoking, healthy weight)
• Tight glucose control in DM

Question 7

How do we limit the progression/complications of CKD?

Answer 7

Blood pressure:

• Even a small BP drop may save significant renal function
• The target BP is < 140/90 (<130/90 if significant proteinuria)
• In diabetic kidney disease, it is recommended to treat with ACEI or ARB even if the BP is normal

Diabetes mellitus:

• Maintain HbA_1C <7%, fasting glucose < 6 mM and post-prandial glucose <7.5 mM

Renal bone disease:

• CKD patients are at risk of developing osteodystophy
  
  • PTH level is monitored and treated if raised as well as phosphate elevation (rises in CKD and causes PTH to increase further and precipitate in vessels)
    
    • Achievable through diet and phosphate-binders that decrease GI absorption
    • Vitamin D analogues and Ca²⁺ supplements can delay bone disease and hyperparathyroidism

Cardiovascular disease:

• In stages 1-2, there is a higher risk of CV death that reaching ESRD
  
  • Statins and low-dose aspirin are used to manage the risk

Diet:

• All patients should be reviewed by a dietetician for advice on healthy, moderate protein diet, K⁺ restriction (if hyperkalemic) and avoid high phosphate foods (milk, eggs, cheese)

Question 8

How do we control symptoms?

Answer 8

Anemia:

• Blood count should be performed routinely
• Iron/B12/folate should be supplemented if necessary
  
  • If still anemia –> recombinant human EPO

Acidosis:

• NaHCO3 supplements for patients with low serum bicarbonate
  
  • This only improves symptoms but may slow progression
  • Caution in patients with HTN as sodium load can increase BP

Edema:

• High doses of loop diuretics may be needed (furosemide, metolazone)
• Restriction of fluid and sodium intake

Restless leg syndrome:

• Low ferritin may worsen symptoms
• Clonazepam and gabapentin may help
• Quinine sulfate can help with cramps

Question 9

What is the last possible treatment for ESRD?

Answer 9

Renal replacement therapy