Renal Tubular Acidosis, Stones, and Nephrocalcinosis

Renal tubular acidosis, particularly the distal form, is commonly associated with renal stones, which are usually made of calcium phosphate, because of the raised urine pH. Despite our greater understanding of the underlying mechanisms of urinary acidification and our ability to detect a clinically significant defect in renal acid excretion, our treatment options remain limited and are aimed mainly at reducing the effect of acidosis on growth and bone mineralization, rather than at decreasing stone recurrence rates or the often associated (and characteristic) nephrocalcinosis. It is a diagnosis that should be considered in all patients with renal stones, especially those with a family history or with associated autoimmune disease, or a low urinary citrate, and a calcium phosphate stone. Many patients are not obviously acidotic (so-called incomplete distal renal tubular acidosis), which is why a screening urinary acidification test is valuable. These aspects of investigating and managing patients with renal stones due to renal tubular acidosis, as well as its underlying mechanisms, are considered in more detail in this chapter.