type II renal tubular acidosis

Type II renal tubular acidosis is caused by impaired proximal renal tubular reabsorption of sodium bicarbonate, resulting in decreased blood levels of this salt and presenting with hyperchloremic acidosis. Because proximal tubular reabsorption of sodium bicarbonate is reduced, more sodium bicarbonate reaches the distal renal tubules. If it exceeds the absorption threshold of the latter, urinary sodium bicarbonate increases and urine pH rises; if blood sodium bicarbonate decreases to a certain level and the renal tubules can completely absorb the sodium bicarbonate in the glomerular filtrate, the urine may become acidic again and urine pH may decrease. In addition, proximal tubular reabsorption of glucose, phosphate, uric acid, and amino acids may also decrease, manifesting as Fanconi syndrome.