Hi Barbi -
Any one of the major disease processes your dad suffers from could contribute to accumulation of fluid in the legs. Poorly controlled diabetes can be a primary cause, or can contribute as a secondary cause due to damge to the kidneys. MS causes loss of muscle tone and in turn the muscles in the legs don't contribute much to blood return sometimes, which can allow fluid to break through the blood cells and collect in the legs. Both these conditions, plus emphysema, can contribute to congestive heart failure, which is one of the most common direct causes of this problem.
The underlying cause or causes will have to be diagnosed and treated and, in the meantime, medication to help reduce the build-up of fluid can afford some relief. Several specialists will likely wind up involved in an effective effort to get your dad's organ systems working in concert again so as to avoid this sort of thing becoming chronic.
I hope this is helpful to you. Good luck to you and to your dad. Please follow up with us as neccessary.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist