Ans. c. Sodium bicarbonate requirement Renal Tubular Acidosis Feature Type I(Distal) Type II(Proximal) Type IV Normal anion gap Yes Yes Yes Minimum urine pH >5.5deg <5.5deg <5.5 A filtered bicarbonate excreted <10 >15 <10 Serum potassium Low Low Highdeg Fanconi's syndrome No Yesdeg No Stones/Nephrocalcinosis Yesdeg No No Daily acid excretion Low Normaldeg Low Urinary anion gap Positive Positive Positive Type 1 (Distal) A In distal A, the kidneys are unable to acidify the urine to pH Treatment Early initiation of alkali replacement at doses equivalent to 1-3 mmol/kg per day of bicarbonate in divided doses will usually correct the acidosis, hypokalemia, and hypocitraturia, maintaining growth and preventing bone disease in early-onset dA. Citrate is generally tolerated better than sodium bicarbonate and can be given as the potassium or sodium salt, depending on the severity of hypokalemia. In patients who present later with kidney stones. large fluid intake and sufficient alkali to restore normal acid-basebalance, correct the hypocitraturia and reduce hypercalciuria, thereby inhibiting the formation of new stones Treatment of Type 2 (Proximal) A It is difficult to restore normal acid-base balance in patients with proximal A despite large amounts of alkali. This is the case because they continue to waste bicarbonate (fractional excretion >15%) until the serum level falls below a threshold, usually about 15-17 mmol/L, at which time bicarbonate is completely reabsorbed distally and the urine is maximally acidified with pH <5.5. When the serum bicarbonate concentration is raised above the threshold with alkali therapy, bicarbonate wasting recurs and causes hypokalemia as potassium is secreted to maintain luminal electroneutrality. Thus, treatment of pA requires 5-15 mmol/kg per day of bicarbonate together with supplemental potassium