What might indicate the possibility of agonal edema in a deceased individual?

The indication of agonal edema in a deceased individual is best demonstrated by swelling upon initial inspection. Agonal edema occurs when there is an accumulation of fluid in the body's tissues prior to death, often due to factors like heart failure or prolonged illness. When a body exhibits swelling—characteristically noticeable in areas such as the extremities, abdomen, or face—this can suggest that fluid has built up in the tissues, indicating the presence of agonal edema.

In the context of the other choices, discoloration of the skin can be associated with various post-mortem changes but is not specifically indicative of agonal edema. A lack of rigor mortis can indicate issues with the cadaver's physiological state, such as a prolonged duration prior to death, but it does not directly signal fluid accumulation. Lastly, the presence of fluid in body cavities is more consistent with post-mortem changes rather than indicating agonal edema itself; it signifies a breakdown and pooling of fluids after death. Focusing on the visible swelling upon initial inspection directly relates to the condition preceding death, making it the most accurate indicator of agonal edema.