My personal opinion is to stay away from these type of supplements/diet pills, etc, but honestly, you would have to talk to your doctor. My understanding of PGX is that it forms a gel-like substance in your stomach to give you a feeling of fullness, thus resulting in eating less. From there, I have no idea how long the gel stays intact or precisely if and how it breaks down. Elimination might not be a problem for folks with colons, but our anatomy is of course very different. Theoretically, if the stuff breaks down easily, then you shouldn't have trouble passing it. But, my number one concern would be obstruction and/or difficulty passing the gel through the pouch if it stays intact. On that note, there is the chance that if the substance does not break down fully, it could accumulate over time in the pouch and cause issues there. Even, for instance, if the only drawback might be thicker output, that alone can be problematic over time with straining, constipation, etc.
Basically, PGX sounds iffy to me, if not potentially dangerous. Not to mention, the idea of a ball of gel sitting in my stomach doesn't sound too appealing. But do talk to your doctor if this is something you want to explore.