Clinical Case Scenario
A 62-year-old diabetic and hypertensive male with chronic kidney disease (CKD) with eGFR) of 50 mL per minute per 1.73 m2 presents with generalized weakness and hyperkalemia. The lab investigations are given below: Lab values: pH: 7.31 HCO₃⁻: 17 mEq/L PaCO₂: 38 mmHg Na⁺: 138 mEq/L K⁺: 6.2 mEq/L Cl⁻: 108 mEq/L Urine pH: 5.0 Urine Na⁺: 25 mEq/L Plasma Aldosterone: Low
Wrong Answer: A) Type 1 (Distal) RTA
Wrong Answer: B) Type 2 (Proximal) RTA
Right Answer:Type 4 RTA → Hypoaldosteronism, Hyperkalemia, Non-Anion Gap Metabolic Acidosis (NAGMA). Urine pH <5.5 suggests intact distal acidification (unlike Type 1 RTA). CKD alone doesn’t explain hyperkalemia without severe GFR decline. Low aldosterone → ↓Na⁺ reabsorption → ↓H⁺ excretion → Acidosis & Hyperkalemia. Renal tubular acidosis (RTA) is a group of disorders affecting the renal tubules, leading to defective acid-base regulation and hyperchloremic normal anion gap metabolic acidosis (NAGMA), often with a normal or mildly reduced glomerular filtration rate (GFR). Type 1 (Distal RTA) is due to impaired H+ secretion in the distal tubule, causing persistent alkaline urine, hyperchloremic acidosis, hypokalemia, and renal stone formation, commonly seen in hereditary conditions, autoimmune diseases, or nephrotoxic exposures. Type 2 (Proximal RTA) results from defective bicarbonate reabsorption in the proximal tubule, leading to bicarbonate wasting, metabolic acidosis, and hypokalemia, often associated with Fanconi syndrome, vitamin D deficiency, or nephrotoxins. Type 4 RTA is characterized by hyperkalemia due to hypoaldosteronism or aldosterone resistance, impairing ammonium excretion and reducing urine buffering capacity, commonly seen in diabetic nephropathy, Addison’s disease, or medication effects. Diagnosis relies on blood and urine pH, bicarbonate levels, electrolyte disturbances, and response to acid or bicarbonate loading tests. Treatment involves correcting acidosis with bicarbonate or citrate, addressing electrolyte imbalances, and managing underlying causes. COMPARISON OF TYPES OF RENAL TUBULAR ACIDOSIS (RTA)
Wrong Answer: D) Lactic acidosis from CKD
