A 52-year-old man with chronic kidney disease stage 4 (eGFR 28 mL/min/1.73m²) presents with serum potassium of 6.8 mEq/L on routine blood work. He is asymptomatic and ECG shows no acute changes. What is the most common cause of hyperkalemia in this patient?

Explanation

## Most Common Cause of Hyperkalemia in CKD **Key Point:** In patients with chronic kidney disease, reduced glomerular filtration rate (GFR) is the most common cause of hyperkalemia. The kidneys are responsible for excreting ~90% of dietary potassium; when GFR falls below 15 mL/min/1.73m², hyperkalemia becomes increasingly prevalent. **High-Yield:** The prevalence of hyperkalemia increases significantly as CKD progresses: - Stage 3 CKD: ~5–10% prevalence - Stage 4 CKD: ~10–15% prevalence - Stage 5 CKD (not on dialysis): ~20–50% prevalence **Clinical Pearl:** Even modest reductions in GFR (Stage 4: eGFR 15–29) can lead to hyperkalemia, especially if dietary intake is not restricted or if medications that block the renin–angiotensin–aldosterone system (ACE inhibitors, ARBs, potassium-sparing diuretics) are used. ### Why Other Options Are Less Common in This Context | Cause | Frequency in CKD | Notes | |-------|------------------|-------| | Decreased renal excretion | **Most common** | Inevitable as GFR declines | | Dietary excess | Common but secondary | Requires very high intake; usually controlled by counselling | | Transcellular shift (acidosis) | Less common | Occurs acutely; usually with metabolic acidosis | | Hemolysis (preanalytical) | Rare | Detected on repeat sampling; pseudohyperkalemia | **Mnemonic — ABCDE of Hyperkalemia Causes:** - **A**ddison's disease / ACE inhibitors / ARBs - **B**eta-blockers / Bleeding (hemolysis) - **C**hronic kidney disease / Catabolism - **D**iuretics (potassium-sparing) / Digoxin toxicity - **E**xcessive intake / Exercise-induced rhabdomyolysis In a patient with Stage 4 CKD, **C** (chronic kidney disease) dominates the differential.