Renal Tubular Acidosis

	Type 1 Distal	Type 2 Proximal	Type 4
Defect	Reduced $\mathrm{H}{}^{+}$ excretion in distal tubule	Impaired $\mathrm{HCO}{}_3{}^{-}$ reabsorption in proximal tubule	Impaired cation exchange in distal tubule
Hyperchloraemic NAGMA	Yes	Yes	Yes
Minimum urine pH	>5.5	<5.5 (but usually >5.5 before acidosis becomes established)	<5.5
Plasma $\mathrm{HCO}{}_3{}^{-}$	<15	>15	>15
Plasma $\mathrm{K}{}^{+}$	low-normal	low-normal	high
Renal stones	yes	no	no