1985 Volume 76 Issue 10 Pages 1429-1438
Urinary citrate excretion was measured in the morning spot urine of 112 calcium stone formers and 87 non-stone formers (control). Citrate excretion was significantly lower in male stone formers than in age-matched male controls, whereas there was no significant difference in citrate excretion between female stone formers and age-matched female controls. But citrate excretion in female recurrent stone formers was significantly lower than that in female single stone formers and controls.
The influence of dietary load on urinary citrate excretion was investigated in 11 male normal healthy subjects. There was no difference in the citrate excretion under the acute load of various diets (standard diet, high protein diet, oxalate-rich diet and high protein and oxalate-rich diet) although citrate excretion correspondingly varied with urine pH under the dietary loads. Also there was a significant direct correlation between citrate excretion and urine pH. However, under the same dietary conditions, the urinary citrate and urine pH in 13 male stone formers were consistently lower than the controls. From these results, we assume that the stone former is in the condition of acid excess, which may be referred to as “subclinical metabolic acidosis”.
For investigation of the effect of ingested animal protein on citrate, calcium and oxalate excretion, three groups of Wistar rats were fed a standard protein diet (SPD), a high protein diet (HPD: added casein to the SPD), or a low protein diet (LPD) for eight days. Citrate excretion in the HPD group was much lower than in the other two groups. Conversely, calcium excretion in the HPD group was higher than that of the other two groups. Oxalic acid excretion in the HPD group was lower than that of the SPD group and was similar to that of the LPD group. One per cent sodium bicarbonate was given orally for eight days ad libitum, with an increase in urine pH, while citrate excretion in the HPD group was much increased to the level of the SPD group. Conversely, calcium excretion in the HPD group decreased to the level of that in the SPD group. Oxalic acid excretion in the HPD group was not affected by sodium bicarbonate. These results showed that overconsumption of animal protein led to acid excess in the body and consequently hypocitraturia and hypercalciuria.
It is sugested that the hypocitraturia of the stone former is mainly due to overconsumption of acid foods which is the important factor in stone formation.
