URINARY ACIDIFICATION AND URINARY-EXCRETION OF CALCIUM AND CITRATE INWOMEN WITH BILATERAL MEDULLARY SPONGE KIDNEY

Urinary acidification ability, acid-base status and urinary excretion of calcium and citrate were evaluated in 10 women with bilateral medul lary sponge kidney (MSK) and in 10 healthy women. Patients with MSK ha d higher fasting urine pH compared to normal controls (p < 0.01). Four patients had incomplete renal tubular acidiosis (iRTA), 3 had hyperca lciuria, and 5 patients had hypocitraturia. The 24-hour urinary excret ion of calcium was increased in the females with MSK (5.23 +/- 0.78 mm ol) compared to the healthy females (3.49 +/- 0.29 mmol) (p < 0.02), a nd increased in MSK patients with iRTA (7.32 +/- 1.45 mmol) compared t o patients with normal urinary acidification (3.83 +/- 0.12 mmol) (p < 0.01). The patients with iRTA had reduced levels of plasma standard b icarbonate (20.5 +/- 1.0) after fasting compared to patients with norm al urinary acidification (23.8 +/- 0.8) and healthy women (22.7 +/- 0. 6) (p < 0.01), and reduced levels of 24-hour urinary excretion of citr ate (0.93 +/- 0.25 mmol) compared to patients with normal urinary acid ification (3.58 +/- 0.51) and healthy women (2.78 +/- 0.49) (p < 0.005 ). A positive correlation was found between the degree of acidosis dur ing ammonium chloride loading and urinary excretion of calcium (r = 0. 71, p = 0.02), and a negative correlation between the degree of acidos is during ammonium chloride loading and urinary citrate excretion (r = 0.87, p = 0.001). The results suggest that defective urinary acidific ation might play an important role in the mechanism of hypercalciuria and hypocitraturia in patients with medullary sponge kidney. Furthermo re, our data suggest that in the group of patients with bilateral MSK there might be two categories. In one category, iRTA is present. The m ain metabolic lithogenic factors in this group appear to be increased urinary excretion of calcium, decreased urinary excretion of citrate a nd increased urine pH. The other category does not have iRTA, and the metabolic abnormalities related to stone disease are much less pronoun ced.