如何使用XPath Query在xml节点中添加字符串内容（空节点/附加到现有内容）

I have the following xml structure already available with the childnodes as title, desc, symp, diag, treat addinfo etc. I want to check that whether addinfo contains any thing and also append some string to it like "This is additional info". There are many disease title I need to check the addifo tag according to disease title-title tag.I have the following xml structure already avai