Table 1.
Summary of renal tubular acidosis classification, diagnostic characteristics, and treatment options
| Distal (type 1) RTA | Proximal (type 2) RTA | Hyperkalemic (type 4) RTA | |
|---|---|---|---|
| Primary defect | Decreased distal acid excretion or increased H+ membrane permeability | Decreased proximal reabsorption of HCO3– | Reduced excretion of acid and K+ in the collecting duct |
| Symptoms | Polydipsia, polyuria, muscle weakness, nephrolithiasis, nephrocalcinosis, growth retardation or failure to thrive, rickets | Muscle weakness or paralysis (if severely hypokalemic), growth retardation in early childhood | Often asymptomatic, occasional muscle weakness of cardiac arrhythmia |
| Urine pH | > 5.3 | < 5.5 | < 5.5 |
| Serum HCO3– | 10–20 mmol/L | 16–20 mmol/L | 16–22 mmol/L |
| Serum K+ | Low (< 3.5 mmol/L) | Low (< 3.5 mmol/L) | High (5.5–6.5 mmol/L) |
| Serum anion gap | Normal | Normal | Normal |
| Diagnostic tests | Positive urinary anion gap after NH4+ loading test |
Fractional excretion of HCO3– > 15% or urine pH > 7.5 after HCO3– loading test Glycosuria, hypophosphatemia, and hypouricemia indicates Fanconi syndrome |
Urinary K+ < 40 mmol/L or fractional K+ excretion < 20%, abnormal serum aldosterone, with near-normal renal function |
| Treatment | |||
| Diet and lifestyle modifications | Increased citrus fruit and fluid intake, restricted intake of Na+, oxalate, fructose, and animal protein, normal Ca2+ intake | Limit acid-based foods (animal source protein), increase alkali-based foods (fruits and vegetables) | Dietary K+ restriction, increase alkali-based foods, limit acid-based foods |
| Pharmacotherapy | NaHCO3 or KHCO3 (1–2 mmol/kg/day), KCl or K-citrate (in patients with severe hypokalemia) | Alkali therapy (usually K-citrate 10–15 mmol/kg/day), fluids, electrolytes, vitamin D, phosphate, hydrochlorothiazide | Low-dose fludrocortisone, loop diuretics (if fludrocortisone not tolerated), oral NaHCO3 if serum HCO3– < 22 mmol/L, K+ binders (patiromer or SZC) |
Ca2+ calcium ion, HCO3– bicarbonate, K+ potassium, KCl potassium chloride, Na+ sodium, NaHCO3 sodium bicarbonate, NH4+ ammonium, RTA renal tubular acidosis, SZC sodium zirconium cyclosilicate