What happens with the capsule being left in when implants explanted under local?

Nothing will happen.  You would need a capsulectomy. For
explant surgery, it is almost always best to remove the capsule in its
entirety. This will allow the space to heal. If you leave the
capsule in place, it does not heal. Fluid can accumulate in the space.
The situation that brings the patient to implant removal will have an
affect on the decision. This is a surgery which requires discussion with
the plastic surgeon about the problem, the goals, and the technical concerns.
The body does not re-absorb the capsule. Revision surgery requires
drains because the fluid is going to be generated when you operate on the scar
capsule. If you provide a mechanism for the fluid to be removed (i.e.
drains), the risks are lower. If the fluid accumulates because there were
no drains, it will most certainly cause problems in the future.

The capsule is simply scar tissue that forms around the implant.  It's a natural occurrence in the body.  If the capsule is thin and not causing issues, it can be left behind.  If it is thickened, it is recommended that it be removed with the implant.  The scar capsule being left behind should not negatively impact a mammogram.

Thank you for your question.  Breast capsules are essentially scars that form inside the breast around the implant.  In general, they are removed along with explantation of the implant especially if the breasts are small and the capsule is thick since it can affect the appearance of the breasts after explantation.  It is hard to predict what the capsule will look or feel like after explantation.  It should not obscure mammograms and the capsule may contract after explantation but that will be minimal.  I recommend having an in-office consultation with a board certified plastic surgeon to help you make the best decision to meet your aesthetic goals.  Good luck and I hope this helps.  

Once implants are put in the body they develop a healing "capsule" made of collagen. Sometimes this capsule is thin and soft and can be left after removal of an implant. It will collapse and melt away with time,once the implant is removed. Other times the capsule is thick and scared and should be removed with the implant when the patient desires explantation. I commonly remove implants, remove 60-70% of the capsule, repair the pectoral muscle, perform an internal purse string tightening of the breast (called an internal mastopexy) and then graft fat to restore fullness. Most patients also require an external mastopexy, or breast lift. With this protocol we can usually achieve a more attractive breast than before the implant was removed. Patients who want a larger breast will require a second fat grafting proceedure.

You would need a GA to remove the capsule and GA is my preference for explantation- although in the UK there are few saline implants placed and my explantation experience is mainly with silicone cohesive gel implants.Local is an option for saline implants and if the capsule is thin (best assessed on an examination) then there are less perceived risks of leaving the capsule - however you won't 100% know until the operation. The problem is that during the op if you need the capsules removed this may not be possible.