Overview
Definition
A defect in aldosterone responsiveness or secretion, leading to impaired distal potassium and hydrogen excretion, characterized by hyperkalemic metabolic acidosis.
Epidemiology
The most common type of RTA. Strongly associated with diabetic nephropathy.
Etiology & Risk Factors
- Hypoaldosteronism or aldosterone resistance
- Associated with diabetic nephropathy (hyporeninemic hypoaldosteronism), NSAIDs, ACE inhibitors, potassium-sparing diuretics
Clinical Symptoms
- Often asymptomatic except for laboratory anomalies
- Cardiac arrhythmias (due to hyperkalemia)
- Muscle weakness
Clinical Approach
Diagnosis
- Normal anion gap metabolic acidosis
- HYPERKALEMIA (distinguishes from Type 1 & 2)
- Urine pH < 5.5 during acidosis
Management
- Low-potassium diet and loop diuretics (Furosemide)
- Fludrocortisone (mineralocorticoid replacement, if aldosterone deficient)
- Oral bicarbonate if needed
Complications
- Severe hyperkalemia / Cardiac arrest
- Arrhythmias