Application of path analysis to urinary findings of cadmium-induced renal dysfunction

In order to identify some causal relations among various urinary indices of cadmium-induced renal dysfunction, such as glucose, total protein, amino n itrogen, Bz-microglobulin (beta (2)-m), metallothionein (MT), and cadmium ( Cd), we applied path analysis method to previous epidemiological studies ta rgeting the residents of the Cd-polluted Kakehashi River basin of Ishikawa Prefecture, Japan. We obtained a diagram-termed path model, representing so me causal relations among the above urinary indices. It shows that urinary Cd is located at the beginning point in the diagram, and Cd-induced renal d ysfunction develops in the following order: Cd exposure --> increase of bet a (2)-m and/or MT excretion --> increase of amino-N and/or total protein ex cretion --> increase of glucose excretion. It was proved mathematically, th at in the case of both males and females, increased excretions of beta (2)- m and/or MT were the most sensitive urinary indices of the early stage of c hronic Cd-induced renal dysfunction.