Could widespread inflammation cause fluid retention?

Yes. Any acute or chronic inflammatory disorder can cause fluid retention by several mechanisms. This generally is secondary to reductions in the serum Albumin level secondary to decreased production, liver disease, renal disease with protein excretion, and protein loss through the gastrointestinal tract. When the protein loss is significant fluid retention(edema) is present.
Yes. the membarane transport is and oncotic pressures are altered. This can lead to fluid retention. More information is needed if you want a definitive answer.