Effect of potassium depletion on urinary stone risk factors in Wistar rats

Various studies have suggested that potassium depletion leads to acidosis and hypocitraturia. In Northeastern Thailand, for example, mild hypokalemia and mild hyperoxaluria are observed in most stone formers. However, there are limited reports about the direct link between potassium depletion and the formation of urinary stones, most of which are calcium oxalate stones. Therefore, we studied the direct effect of potassium depletion on the risk factors for calcium oxalate stone formation. Seventy-two rats were fed a control diet or a potassium-deficient diet for 1, 2, or 3 weeks (n = 12 per group). Twenty-four-hour urine collection was done for the measurement of potassium, calcium, oxalate, glycolate, citrate, phosphorus, and magnesium. Lactate dehydrogenase activity was also measured in order to assess renal tubular damage, and kidneys were harvested for histological examination. Furthermore, urinary supersaturation of calcium oxalate was calculated. With potassium depletion, the urinary concentrations of potassium, citrate, magnesium, and phosphorus decreased rapidly. There was no detectable renal damage, renal calcium deposition, and no significant increase of urinary oxalate or calcium. However, the urinary supersaturation index of calcium oxalate increased significantly in rats with potassium depletion. These findings indicate that potassium deficiency may increase the risk of stone formation through enhanced supersaturation.