hi Sam and welcome. I will copy and paste some info for you to read, it could be just scar tissue..however if there is any warmth or seepage its than likely theres an internal infection going on. I would read the following carefully and if you are at all concerned that something is not right than take her back to her Vet asap....there should be NO charge for any followup care after surgery..this is all part of the costs, so don't hesitate to consult the Vet.
6d. Wound infection.
The causes of wound infection bear many similarities to those mentioned in section 6c and infection of surgical incision-sites can often lead to secondary wound break-down.
Wound infection occurs when bacterial organisms gain access to the surgical incision site and multiply there in large numbers. The bacterial invasion causes damage to the body tissues at the site of infection (this limits the healing of tissues in the spay site) and triggers a secondary immune system attack on the infected region, resulting in inflammation (redness, swelling, heat) and a build up of pus (invading white blood cells produce yellow, green or red-brown discharges) in the area.
Owners often first notice infection when the spay incision line becomes sore, swollen, red and hot-to-touch. Sometimes, the pet will tell the owner that it is in pain by licking the infected regions obsessively: infection should certainly be suspected if a pet goes from initially not being bothered by its wounds to licking and biting at them excessively. Within hours to days of this redness and inflammation being noticed, the owner may witness a yellow to green purulent discharge (pus) coming from the suture holes or the incision line itself. If allowed the progress, the wound may split apart completely, resulting in wound breakdown. Sometimes, if the skin incision site has sealed over but the infection has gained access to the deeper subcutaneous fatty tissues, pus and infection will build up underneath the skin producing a painful pus-filled swelling called an abscess. When the abscess bursts, large amounts of pus will drain out of the area.
Wound infection is very uncommon in most routine desexing surgeries and most commonly occurs because of poor home care. It tends to occur because the pet was allowed to lick the sutureline and, consequently, introduce mouth bacteria into the surgical incision. Infection also tends to occur if the sutures are allowed to get wet (the animal was bathed, allowed to go swimming, allowed to lay in mud) or if the sutures are allowed to become soiled by faeces, urine or dirt. Wound infection may also occur if the vet performs the surgery on an animal with diseased allergic or infected belly skin. Bacterial numbers are very high in diseased skin and will easily enter the wound site during surgery, regardless of the amount of pre-surgical prepping done.
Very occasionally, wound infection may also be a result of poor surgical technique (e.g. vets not wearing gloves to do surgery); poor skin preparation technique before surgery; a freak bug entering the surgical site (sometimes nasty bacteria like Golden Staph and flesh-eating Streptococcus and Mycobacteria species will find their way into a vet clinic and cause havoc) or the animal having a poor or compromised immune system. Animals with Cushing's disease, Diabetes Mellitus, FIV, FeLV and other immune suppressive disorders may be more prone to wound infections.
Wound infection is definitely cause to see your vet. If the wound infection is only mild, the animal may only require antibiotic coverage; an Elizabethan collar and better home care to treat the problem. If the wound has completely abscessated and is at risk of falling apart, the vet may need to operate on your pet again to retrim and repair and clean the surgical wound. Healing will then take another full 10-14 days to occur.
6e. Suture-site reactions - swollen, red skin around sutures or stitches (uncommon).
Suture site reactions refer to allergic-type, inflammatory skin reactions that some cats and other animals develop because of the type of suture being used in the surgical incision repair. Basically, suture site reactions are immune-mediated inflammatory reactions that occur when the cat's body decides to reject the foreign bodies (the sutures or stitches) that the vet has just implanted into the skin. True suture site reactions are not that common (modern day sutures are normally very inert and non-reactive) and most so-called suture site reactions are actually wound infections or break-downs caused by all of the factors mentioned in sections 6c and 6d.
When suture site reactions do occur, what tends to happen is that the animal develops signs of inflammation (redness, swelling, heat, maybe even a serous (watery) or ***** discharge) around the suture holes themselves, but not along the surgical incision line in general.
i.e. The reaction is centred around the sutures, but the rest of the surgery site appears fine.
Author's note - early bacterial infections can mimic suture-line reactions if the bacteria have gained access to the body tissues by traveling up the sutures. In these cases, the inflammatory reaction will also be centred around the sutures because this is where the bugs are lurking. Untreated, however, such bacterial infections will usually spread and become more generalized (i.e. involve all of the incision line), whereas true suture-line reactions should remain localized and focussed upon the stitches.
Usually what happens with true suture site reactions is that the wound incision itself heals up fine because the reaction is centred around the sutures only. Once the sutures are removed (usually after the surgical site has healed), the problem usually resolves on its own. If the condition is severe and the wound healing itself is becoming secondarily compromised by the suture reaction, the vet may elect to remove the skin sutures early to let everything settle down again and heal. This does, however, pose a risk of the main wound breaking down prematurely. In most cases, especially mild cases, the vet will elect to leave in the sutures until the main wound has healed and then remove the sutures to let the suture reaction resolve.
To prevent the problem in the future, a different type of suture material should be selected for that animal.