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<span>　　<span lang=\"EN-US\">(</span>二<span lang=\"EN-US\">)</span>发病机制<span lang=\"EN-US\"></span></span>

<span>　　混合型<span lang=\"EN-US\">RTA</span>发病机制应与Ⅰ、Ⅱ型<span lang=\"EN-US\">RTA</span>相似。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">1.</span></span><span lang=\"EN-US\"> H⁺</span><span>[[主动转运]]致管腔速度降低<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(1)</span>梯度缺陷：</span><span lang=\"EN-US\">H⁺</span><span>转运对管腔<span lang=\"EN-US\">H+(</span>管腔<span lang=\"EN-US\">-</span>[[细胞]]或管腔<span lang=\"EN-US\">-</span>小管周围<span lang=\"EN-US\">H+</span>梯度<span lang=\"EN-US\">)</span>的抑制作用异常敏感，其主动转运速度降低。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(2)</span></span><span lang=\"EN-US\"> H⁺</span><span>分泌缺陷：即使解除</span><span lang=\"EN-US\">H⁺</span><span>浓度的抑制后，</span><span lang=\"EN-US\">H⁺</span><span>由细胞向管腔转运仍低于正常，分泌能力降低。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">2.</span></span><span lang=\"EN-US\"> H⁺</span><span>从管腔到细胞<span lang=\"EN-US\">(</span>或到间质<span lang=\"EN-US\">)</span>弥散速度增加<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(1)</span></span><span lang=\"EN-US\"> H⁺</span><span>[[反流]]增加：小管[[上皮细胞]]腔[[面膜]]或[[紧密连接]]对</span><span lang=\"EN-US\">H⁺</span><span>通透性增加，使</span><span lang=\"EN-US\">H⁺</span><span>由管腔向细胞内反流。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(2)</span>依赖电压的</span><span lang=\"EN-US\">H⁺</span><span>转运缺陷：因管腔<span lang=\"EN-US\">[[Na]]</span></span>^{<span lang=\"EN-US\">+</span>}<span>吸收减少或<span lang=\"EN-US\">Cl</span></span>^{<span lang=\"EN-US\">-</span>}<span>[[重吸收]]增加，降低了管腔的负电荷，降低了</span><span lang=\"EN-US\">H⁺</span><span>的分泌或增加了</span><span lang=\"EN-US\">H⁺</span><span>的反流。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">3.</span>重吸收</span><span lang=\"EN-US\">HCO₃^-</span><span>的能力下降 正常人</span><span lang=\"EN-US\">HCO₃^-<span>85%</span></span><span>在[[近曲小管]]被重吸收，近曲小管酸化功能受损害时，重吸收</span><span lang=\"EN-US\">HCO₃^-</span><span>的能力下降，过多的</span><span lang=\"EN-US\">HCO₃^-</span><span>从尿中排出，这种碳酸氢盐的耗失，使血中</span><span lang=\"EN-US\">HCO₃^-</span><span>含量下降，形成[[酸中毒]]和碱性尿。</span>

<span>　　<span lang=\"EN-US\">1.</span>[[血液]]化验 主要表现血<span lang=\"EN-US\">K⁺</span>、<span lang=\"EN-US\">[[Ca]]² ⁺ </span>、<span lang=\"EN-US\">[[Na]]⁺</span>、<span lang=\"EN-US\">PO₄^3-</span>偏低，血<span lang=\"EN-US\">Cl-</span>增高，[[血浆]]<span lang=\"EN-US\">HCO₃^-</span>减少，<span lang=\"EN-US\">CO2</span>结合力降低血氯升高，血<span lang=\"EN-US\">HCO₃^-</span>降低，血钾正常或降低。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">2.</span>尿液化验 尿中无细胞成分，<span lang=\"EN-US\">HCO₃^-</span>[[排泄]]分数多<span lang=\"EN-US\"><5%</span>，尿<span lang=\"EN-US\">NH₄⁺<500mmol/d</span>，<span lang=\"EN-US\">24h</span>尿<span lang=\"EN-US\">K⁺</span>、<span lang=\"EN-US\">Ca² ⁺ </span>、<span lang=\"EN-US\">Na⁺</span>、<span lang=\"EN-US\">PO₄^3--</span>排出增多。尿<span lang=\"EN-US\">pH>5.5</span>，尿钾排泄量增加。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">3.</span>负荷试验<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(1)</span>[[氯化铵]]试验：对可疑和不完全性<span lang=\"EN-US\">Ⅰ</span>型<span lang=\"EN-US\">[[RTA]]</span>常用试验<span lang=\"EN-US\">;</span>给受试者氯化铵<span lang=\"EN-US\">0.1g/(kg.d)</span>，分<span lang=\"EN-US\">3</span>次口服，连续<span lang=\"EN-US\">3</span>天。第<span lang=\"EN-US\">3</span>天每小时留尿<span lang=\"EN-US\">1</span>次，测尿<span lang=\"EN-US\">pH</span>及血<span lang=\"EN-US\">HCO₃^-</span>，当血<span lang=\"EN-US\">HCO₃^-</span>降至<span lang=\"EN-US\">20mmol/L</span>以下时而尿<span lang=\"EN-US\">pH>5.5</span>，有诊断价值。有[[肝病]]者改用[[氯化钙]]<span lang=\"EN-US\">1mmol/(kg.d)</span>，方法与阳性结果的判定同氯化铵负荷试验。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(2)</span>尿铵测定：正常人尿铵排泄量约为<span lang=\"EN-US\">40mmol/d</span>，<span lang=\"EN-US\">Ⅰ</span>型<span lang=\"EN-US\">RTA</span>尿铵排泄量<span lang=\"EN-US\"><40mmol/d</span>。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(3)</span>尿<span lang=\"EN-US\">PCO2</span>测定：<span lang=\"EN-US\">5%</span>[[碳酸氢钠]][[静脉滴注]]， 使血<span lang=\"EN-US\">pH</span>维持在<span lang=\"EN-US\">0.5h</span>以上<span lang=\"EN-US\">;</span>当尿<span lang=\"EN-US\">pH></span>血<span lang=\"EN-US\">pH</span>时，尿<span lang=\"EN-US\">PCO2></span>血<span lang=\"EN-US\">PCO2 2.66kPa</span>或更多则有诊断意义。即一旦尿液呈碱性，无论血<span lang=\"EN-US\">HCO₃^-</span>浓度是否恢复正常，如尿<span lang=\"EN-US\">PCO2>9.3kPa</span>可认为集合管<span lang=\"EN-US\">H+</span>分泌能力无异常。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(4)</span>尿[[胱氨酸]]检查：[[近曲小管]]疾患时常存在[[胱氨酸尿]]，如阳性则有助于诊断<span lang=\"EN-US\">(</span>氰化物硝基氢氰酸盐试验：取尿液<span lang=\"EN-US\">5ml</span>加[[浓氨水]]<span lang=\"EN-US\">1</span>滴，<span lang=\"EN-US\">5%</span>的氰化钠<span lang=\"EN-US\">3</span>滴，呈紫红色反应为阳性<span lang=\"EN-US\">)</span>。在[[酸负荷试验]]中，如尿<span lang=\"EN-US\">pH<5.5</span>或更低，则诊断<span lang=\"EN-US\">Ⅱ</span>型<span lang=\"EN-US\">RTA</span>的亚型。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">(5)</span>碱负荷试验：<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">①</span>口服碳酸氢钠法：从<span lang=\"EN-US\">1mmol/(kg.d)</span>开始，逐天加量至<span lang=\"EN-US\">10mmol/(kg.d)</span>，[[酸中毒]]被纠正后，测血、尿<span lang=\"EN-US\">HCO₃^-</span>浓度与[[肾小球滤过率]]，计算尿<span lang=\"EN-US\">HCO₃^-</span>的百分率：尿中<span lang=\"EN-US\">HCO₃^-</span>量<span lang=\"EN-US\">=</span>尿<span lang=\"EN-US\">HCO₃^- (mmol/L)×</span>[[尿量]]<span lang=\"EN-US\">(ml/min)/</span>血浆<span lang=\"EN-US\">HCO₃^- (mmol/L)×GFR</span>。正常人尿<span lang=\"EN-US\">HCO3-</span>为零<span lang=\"EN-US\">;Ⅱ</span>型、混合型<span lang=\"EN-US\">RTA>15%</span>，<span lang=\"EN-US\">Ⅰ</span>型<span lang=\"EN-US\">RTA<3%</span>～<span lang=\"EN-US\">5%</span>。<br /><br /><span lang=\"EN-US\"> ②</span>[[静脉滴入]]碳酸氢钠法：以<span lang=\"EN-US\">4ml/min</span>的速度滴入<span lang=\"EN-US\">5%NaHC03</span>，持续<span lang=\"EN-US\">2h</span>。注入前测患者血<span lang=\"EN-US\">pH</span>、<span lang=\"EN-US\">PCO₂</span>、<span lang=\"EN-US\">HCO₃^-</span>浓度和尿<span lang=\"EN-US\">pH</span>、<span lang=\"EN-US\">HCO₃^-</span>浓度<span lang=\"EN-US\">;</span>以后分别在注入<span lang=\"EN-US\">30</span>，<span lang=\"EN-US\">90min</span>后测血<span lang=\"EN-US\">pH</span>、<span lang=\"EN-US\">PCO₂</span>、<span lang=\"EN-US\">HCO₃^-;60</span>，<span lang=\"EN-US\">120min</span>测尿<span lang=\"EN-US\">pH</span>和<span lang=\"EN-US\">HCO₃^-</span>，在患者血<span lang=\"EN-US\">HCO₃^-</span>恢复正常时，尿中<span lang=\"EN-US\">HCO₃^-</span>排泄量<span lang=\"EN-US\">></span>[[肾小球]]滤过量的<span lang=\"EN-US\">15%</span>，提示近曲小管<span lang=\"EN-US\">HCO₃^-</span>[[吸收障碍]]。尿<span lang=\"EN-US\">HCO₃^-</span>排泄分数<span lang=\"EN-US\">=(</span>尿<span lang=\"EN-US\">HCO₃^-/</span>血浆<span lang=\"EN-US\">HCO₃^-/(</span>尿[[肌酐]]<span lang=\"EN-US\">/</span>血肌酐<span lang=\"EN-US\">)</span>。血浆<span lang=\"EN-US\">HCO₃^-</span>浓度正常时，<span lang=\"EN-US\">Ⅱ</span>型<span lang=\"EN-US\">RTA HCO₃^-</span>排泄分数<span lang=\"EN-US\">>15%</span>，<span lang=\"EN-US\">Ⅰ</span>型<span lang=\"EN-US\">RTA<5%</span>。此法可鉴别<span lang=\"EN-US\">Ⅰ</span>型、<span lang=\"EN-US\">Ⅱ</span>型<span lang=\"EN-US\">RTA</span>。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">4.</span>[[影像学]]检查<span lang=\"EN-US\"> KUB</span>平片或<span lang=\"EN-US\">IVP</span>片中可发现鱼籽样[[肾结石]]。并可了解[[骨病]]情况。<span lang=\"EN-US\"></span></span>

<span>　　<span lang=\"EN-US\">5.</span>[[超声波]]检查 可了解[[肾脏]]有无[[钙化]]及[[结石]]。<span lang=\"EN-US\"></span></span>