Upper abdominal swelling 9 months after tummy tuck. What could this be from? (Photo)

Swelling of the upper abdomen nine months after surgery could result from a separation of the muscle repair, as you already mentioned, or it could be where the fatty tissue is thicker than the surrounding areas, or it may be an area just above the muscle repair where there is still space for the abdominal contents to expand a bit, as you've noted when you eat or drink.Your surgeon can examine you and explain what he/she feels. The amount of fatty tissue a patient has deep to the 6-pack muscles can affect the contour. (See link below.) Patients with less intra-abdominal fatty tissue typically have a flatter contour after surgery than those with a more rounded contour to begin with.

It would be difficult to say without knowing what you looked like preoperatively as it could be swelling or excess fat.  But I think it is internal swelling that is causing the bulge as you say it worsens when you eat or drink.  I would go see a gastroenterologist.  Best of luck.