Hoppe Bernd, von Unruh Gerd E, Blank Gesa, Rietschel Ernst, Sidhu Harmeet, Laube Norbert, Hesse Albrecht
University Children's Hospital Cologne, Germany, USA.
Am J Kidney Dis. 2005 Sep;46(3):440-5. doi: 10.1053/j.ajkd.2005.06.003.
Hyperoxaluria has been incriminated to account for the increased incidence of urolithiasis or nephrocalcinosis in patients with cystic fibrosis (CF). Hyperoxaluria presumably is caused by fat malabsorption and the absence of such intestinal oxalate-degrading bacteria as Oxalobacter formigenes. To better elucidate its pathophysiological characteristics, we prospectively studied patients with CF by determining these parameters and performing renal ultrasonography twice yearly.
In addition to routine tests in urine (lithogenic and stone-inhibitory substances), the presence of O formigenes was tested in stool, plasma oxalate was measured, and a [13C2]oxalate absorption test was performed in 37 patients with CF aged 5 to 37 years (15 females, 22 males) who were constantly hyperoxaluric before the study.
Hyperoxaluria (oxalate, 46 to 141 mg/1.73 m2/24 h [0.51 to 1.57 mmol/1.73 m2/24 h]; normal, < 45 mg/1.73 m2/24 h [< 0.5 mmol/1.73 m2/24 h]) was now found in 24 patients (64.8%). Plasma oxalate levels were elevated in 6 patients (7.92 to 19.5 micromol/L; normal, 6.3 +/- 1.1 micromol/L). Oxalobacter species were detected in only 1 patient. Intestinal oxalate absorption was elevated (11.4% to 28.5%; normal, < 10%) in 23 patients. Hypocitraturia was present in 17 patients (citrate, 0.35 to 2.8 g/1.73 m2/24 h [0.2 to 1.1 mmol/1.73 m2/24 h]; normal female, > 2.8 mg/1.73 m2/24 h [> 1.6 mmol/1.73 m2/24 h]; male, > 3.3 mg/1.73 m2/24 h [> 1.9 mmol/1.73 m2/24 h]). Urine calcium oxalate saturation was elevated in 17 patients (5.62 to 28.9 relative units; normal female, < 5.5 relative units; male, < 6.3 relative units). In 16% of patients, urolithiasis (n = 2) or nephrocalcinosis (n = 4) was diagnosed ultrasonographically.
Absorptive hyperoxaluria and hypocitraturia are the main culprits for the increased incidence of urolithiasis and nephrocalcinosis in patients with CF. We advocate high fluid intake, low-oxalate/high-calcium diet, and alkali citrate medication, if necessary. Additional studies are necessary to determine the influence of Oxalobacter species or other oxalate-degrading bacteria on oxalate handling in patients with CF.
高草酸尿症被认为是囊性纤维化（CF）患者尿路结石或肾钙质沉着症发病率增加的原因。高草酸尿症可能是由脂肪吸收不良以及缺乏产甲酸草酸杆菌等肠道草酸降解细菌引起的。为了更好地阐明其病理生理特征，我们通过测定这些参数并每年进行两次肾脏超声检查，对CF患者进行了前瞻性研究。
除了对尿液中的常规检测（致石和抑石物质）外，还检测了粪便中产甲酸草酸杆菌的存在，测定了血浆草酸水平，并对37例年龄在5至37岁（15名女性，22名男性）的CF患者进行了[13C2]草酸吸收试验，这些患者在研究前一直存在高草酸尿症。
现在在24例患者（64.8%）中发现了高草酸尿症（草酸，每1.73平方米/24小时46至141毫克[0.51至1.57毫摩尔/1.73平方米/24小时]；正常，<45毫克/1.73平方米/24小时[<0.5毫摩尔/1.73平方米/24小时]）。6例患者（7.92至19.5微摩尔/升；正常，6.3±1.1微摩尔/升）的血浆草酸水平升高。仅在1例患者中检测到草酸杆菌属。23例患者的肠道草酸吸收增加（11.4%至28.5%；正常，<10%）。17例患者存在低枸橼酸尿症（枸橼酸盐，每1.73平方米/24小时0.35至2.8克[0.2至1.1毫摩尔/1.73平方米/24小时]；正常女性，>2.8毫克/1.73平方米/24小时[>1.6毫摩尔/1.73平方米/24小时]；男性，>3.3毫克/1.73平方米/24小时[>1.9毫摩尔/1.73平方米/24小时]）。17例患者（5.62至28.9相对单位；正常女性，<5.5相对单位；男性，<6.3相对单位）的尿草酸钙饱和度升高。16%的患者经超声检查诊断为尿路结石（n = 2）或肾钙质沉着症（n = 4）。
吸收性高草酸尿症和低枸橼酸尿症是CF患者尿路结石和肾钙质沉着症发病率增加的主要原因。我们提倡大量饮水、低草酸/高钙饮食，并在必要时使用枸橼酸碱剂。需要进一步研究以确定草酸杆菌属或其他草酸降解细菌对CF患者草酸代谢的影响。
