尿路結石症の発生原因に関する検討(第6報)-食生活が尿中クエン酸産非泄量に及ぼす影響について- URINARY CITRATE EXCRETION IN RENAL STONE DISEASE : Effects of Dietary Source
尿路結石症患者の尿中クエン酸排泄量(Cit)を測定し,Citに及ぼす食事の影響を臨床ならびに動物実験で検討した.早朝第1尿で検討した結石患者のCitは,男子結石患者では同年齢層の男子対照群に比して著明に減少していたが,女子結石患者では対照群と差を認めなかった.しかし再発・多発結石患者のCitは著明に減少していた.男子健康成人による各種食事を急性負荷し,食事の種類によるCitの差を検討したが,食後6時間目までのCitに差は認められなかった.各種食事負荷によるCitの動きは尿pHの変動とよく一致し,また食事前後のCitと尿pHの間には有意な正の相関が認められた.食事負荷による結石患者のCitと尿pHは対照群より低値を示すものの,対照群と同様の変動を示した.Wistar系ラットを蛋白質含有量の違う飼料で飼育すると,高蛋白質食を与えた群では標準食を与えた群に比べて有意な低クエン酸尿症,高Ca尿症,尿pHの低下を認めたが,同時に1%重炭酸ソーダ水を与えることによりこれらの状態は是正された.尿中蓚酸排泄量は差を認めなかった.以上の結果から,結石患者にみられる低クエン酸尿症は動物性蛋白質に代表される酸性食品の慢性的な摂取過多に起因すると考えた.すなわち結石患者には慢性の"sucblinical metabolic acidosis"とでもいうような状態が存在し,これが高Ca尿症や低クエン酸尿症を引き起こす大きな要因になると考えた.
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.
日泌尿会誌 76, 1429-1438, 1985