Figure 113

Nephrocalcinosis represents calcification of the renal parenchyma. It is primarily medullary in most cases except in dystrophic calcification associated with inflammatory, toxic, or ischemic disease. Nephro-calcinosis can be seen in association with chronic or severe hypercal-cemia or in a variety of hypercalciuric states. The spectrum of causes of nephrocalcinosis is described by Wrong [3]. The numbers represent the percentage of the total of 375 patients. It is likely that the case mix is affected to some extent by Wrong's interests in, eg, renal tubular acidosis (RTA) and Dent's disease, but this is by far the largest published series. As in other studies, the most important causes of nephrocalcinosis are primary hyperparathyroidism, distal RTA, and medullary sponge kidney. The primary factor predisposing patients to renal calcification in many of these conditions is hypercalciuria, as occurs in idiopathic hypercalciuria, Dent's disease, milk-alkali syndrome, sarcoidosis, hypervitaminosis D, and often in distal RTA. In distal RTA and milk-alkali syndrome, relative or absolute urinary alkalinity promote precipitation of calcium phosphate crystals in the tubular lumena, and hypocitraturia is an important contributing factor in distal RTA. Causes of cortical nephrocalcinosis in this study included acute cortical necrosis, chronic glomerulonephritis, and chronic pyelonephritis.

Impaired urinary acidification

Hypokalemia

Decreased urinary citrate excretion

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