The phrase "most distend" can be a little tricky to find synonyms for, since "distend" itself is somewhat uncommon and not frequently used. However, some possible alternatives might include "most swollen", "most bloated", "most inflated", or "most expanded". These words all imply a sense of enlargement or fullness, which is similar to the connotation of "distend". Other related terms might include "most dilated", "most stretched", or "most bulging", which also carry a sense of expansion or swelling. Ultimately, the choice of which synonym to use will depend on the context and intended meaning of the phrase you're trying to convey.