Is this swelling, muscle repair failure, or fat? (Photo)

Hi, thanks for your question and photos. Swelling after a tummy tuck/ abdominoplasty is normal, however, I would agree that yours seems a little excessive. I always aim for a SLIGHT convexity to the lower abdomen when performing a woman's abdominoplasty, as a completely flat lower abdomen looks a little unnatural and aesthetically less pleasing. I would suggest an ultrasound at this stage, especially if the swelling seems to have gotten worse. This should differentiate fluid accumulation, failure of muscle repair and plication, significant residual fatty tissue above the muscle layer and intra-abdominal fat surrounding your organs and causing an internal bulge. Once a cause is found a plan of management can be initiated. Your specialist plastic surgeon is the best person to assist you at this stage, particularly if further surgery is required. You'll be in good hands. 

Thank you for the question and pictures.  I think that you have a good understanding of the "differential diagnosis”; unfortunately, online consultants, without the benefit of in-person examination will not be able to be very helpful to you when it comes to making an accurate diagnosis or treatment recommendations
 In other words it is best to be seen in person ( by your plastic surgeon) for precise diagnosis and treatment.
 Generally speaking, abdominal wall "swelling" after tummy tuck may be related to:
1. Swelling in the soft tissues.  This may take several months to resolve and may worsen with increased activity  or at the end of the day.   Patience  is required to allow for resolution of the swelling. The swelling occurs because of the interruption of venous and lymphatic channels that occurs during the tummy tuck operation.
2. Fluid accumulation in the space between the skin and the abdominal wall muscle.  this may consist of blood ( hematoma)  or serum (seroma).  This fluid accumulation can generally be diagnosed by physical examination ( occasionally ultrasound  may be helpful).  Treatment consists of aspiration;  several episodes of aspiration may be necessary. 
3. Separation of the abdominal wall muscle repair may lead to a swelling/bulge appearance. This may be diagnosed on physical examination  with your surgeon examining you in different bodily positions. One of the steps of a tummy tuck procedure involves reapproximation (plication)  of the rectus muscles.  These muscles have spread apart during pregnancy and/or weight gain. Bringing them together again in the midline helps to “tighten” the abdominal wall as well as to narrow the waistline.
4. Residual adipose tissue may be confused for swelling. Again this is most easily diagnosed by physical examination. Additional liposuction surgery maybe necessary to improve the results of surgery.
Generally, it takes many months for swelling to resolve after tummy tuck surgery and it may take up to one year  (or greater)  a complete skin redraping  to occur.
I hope this helps.

There is still swelling but there is probably always going to be some swelling. The question is whether this is due to abdominal wall weakness that you have preop and whether this could be improved further, whether it is due to fluid, fat etc. You should consult with your PS but there are limitations of tummy tuck and often it is not possible to completely flatten the whole abdo in patients such as yourself.