Some Features of Different Types of Renal Tubular Acidosis*

Incidence

Rare

Very rare

Common

Mechanism

Impaired hydrogen ion excretion

Impaired bicarbonate resorption

Decrease in aldosterone secretion or activity

Plasma bicarbonate (mEq/L or mmol/L)

Frequently <15, occasionally < 10

Usually 12–20

Usually > 17

Plasma potassium

Usually low but tends to normalize with alkalinization

Usually low and decreased further by alkalinization

High

Urine pH

> 5.5

> 7 if plasma bicarbonate is normal

< 5.5 if plasma bicarbonate is depleted (eg, < 15 mEq/L, or 15 mmol/L)

< 5.5