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: CT scan of the abdomen revealed markedly thickened antrum of the stomach , duodenum and jejunum , along with fluid in the abdominal and pelvic cavity .
### Output Text:
CT scan of the abdomen revealed markedly thickened antrum of the stomach , duodenum and jejunum , along with fluid in the abdominal and pelvic cavity . 