A Seroma is a collection of post-operative fluid that can have a compressive effects. However. if you had “dye” (gadolinium), that should be helpful enough to distinguish fluid collection from recurrent herniation. It could be helpful to get some simple lab tests to make sure this is not infection (but normally the radiologist can distinguish fluid from infection-but not always). If your symptoms are increasing and especially if you have increased weakness, I would recommend some type of action (either an aspiration or an exploration).
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.