Pleural Cavity Effusion

This is an observational study to see how a simple test can be used to check if fluid in the chest cavity contains starch. Some people with kidney failure have dialysis treatment by putting fluid in the tummy cavity, and sometimes the fluid can leak into the chest cavity. Iodine can change the colour of starch based dialysis fluid, so this test could be used to diagnose fluid leaking from the tummy cavity into the chest cavity. The investigators are doing this study to ensure the fluid doesn't change colour for other reasons.