In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Therefore , in adult patients affected by HUS , dialysis should not be discontinued prematurely ; moreover , bilateral nephrectomy , for treatment of severe hypertension and microangiopathic hemolytic anemia , should be performed with caution .
### Output Text:
Therefore , in adult patients affected by HUS , dialysis should not be discontinued prematurely ; moreover , bilateral nephrectomy , for treatment of severe hypertension and microangiopathic hemolytic anemia , should be performed with caution . 