Is it possible for a seroma to develop 6-8 months after Tummy Tuck surgery, no drains?

It is possible you have a seroma, but it is very uncommon this amount of time after surgery.  An ultrasound can show whether your lump is fluid or not.  The first treatment, if it is a seroma, is aspiration and compression.  Please see your surgeon again and kindly ask for an ultrasound.

I have not seen this happen, but this could be diagnosed with needle aspiration and if negative, then an ultrasound to see if the lump is solid or fluid-filled. If fluid it makes sense to treat it sooner rather than later, so it does not become a bursa.  If a bursa forms, then a non-surgical treatment that has  been used injecting it with tetracycline solution.  That can cause it to collapse.  If that were ineffective, surgery would be needed to remove it, which perhaps could be done through the umbilicus. It is good to avoid seromas which drainless tummy tucks are very good at preventing, since treatment involves one or more of the steps above.Drainless tummy  tucks are an integral part of my procedure.  Even with drains or tissue glue there is a a 5-45 % incidence of seroma per the literature. A meta-analysis in the Aesthetic Surgery Journal, 

Aesthet Surg J. 2017 Mar 1;37(3):316-323. doi: 10.1093/asj/sjw192.

Seretis K, Goulis, D, Demiri EC, Lykoudis, EG

Prevention of Seroma Formation Following Abdominoplasty: A Systematic Review and Meta-Analysis

reviewed all the literature on this topic, and found that "preventive measures" decreased the incidence of seroma four-fold. One of the studies included in the "preventive group" that used only progressive tension sutures, from 2006, showed fluid accumulation between the sutures, detected only on ultrasound. This fluid was not clinically detectable by palpation or inspection and resulted in no need for seroma aspiration or any complication. The total amount of fluid associated with clinical complications including drainage in the other groups was greater than 80 cc, and the total amount of non-clinically detectable fluid in the progressive-tension group was always 80 cc or less. The use of drains plus progressive tension sutures did not change the amount of fluid, so there is really no benefit to using drains plus progressive tension sutures.

The study was discussed by Pollock and Pollock, who noted that in their series of 565 patients using progressive tension sutures they never had a clinically significant seroma. When a seroma occurs, it may require multiple visits and aspirations, and if persistent, introduction of antibiotic sclerosing solutions, or reoperation to remove a fluid filled fibrous cavity. The drain opening may leave a scar in the incision or pubic mons which may become pigmented or depressed. Not having to use drains spares the patient and plastic surgeon from the chance of these undesirable events and/or outcomes.

My experience mirrors that of Drs. Pollack.  I have had no clinically significant seromas while using progressive tension sutures in the past five years or so.
Rather than use the 15-20 individually-placed sutures described by Drs. Pollock, I completely close the dead space with continuous PDO and monoderm Quill sutures. These sutures effectively reduce the dead space to almost nothing, so even the small amount of fluid that might collect between the sutures, cannot create any significant seroma. Using running Quill sutures allows relatively rapid dead space closure as no knot-tying is needed. The umbilical location is confirmed with a Lockwood flap marker before the lower abdominal closure is completed.

While most seromas are discovered shortly after the drains are removed and there is an obvious fluid wave there can be seromas form later if there is trauma to the area or hematomas. This could have been a small seroma not recognized early on but developed a thick bursa and then contracted into a more round hard mass just now being discovered. Yes an US can help diagnose a seroma bursa and differentiate from a hernia that you would not want to stick with a needle.

It is possible that you could have a late seroma 6 - 8 months following a drainless tummy tuck, but that would be rare for that point of your recovery.  More likely scenarios are that this is a late hematoma that was either undiagnosed previously and has formed into scar tissue, or a recent trauma has caused a new hematoma near your belly button.  Another possibility is that you have a small area of fat necrosis from a lack of blood supply to that area of the abdominal flap at the time of surgery.  An ultrasound can be performed to determine if there is fluid present or the lump is completely solid throughout.  If this is just scar tissue from any of the previously mentioned causes, it will likely continue to improve with scar massage up to 1 year postop.  I would recommend following up with your plastic surgeon to express your concerns and allow for a thorough physical examination and further recommendations.  Good communication between patient and surgeon is very important both before and after surgery.  Best of luck in your recovery!
Ziyad Hammoudeh, MD@drhammoudehMayo Clinic-trained, Double Board-Certified Plastic SurgeonDiplomate, American Board of Plastic SurgeryDiplomate, American Board of Surgery

and if this occurs, its necessary to try to figure out why this is happening.  Ultrasounds will help determine if you do have fluid collections if there is any doubt.  It will also help determine the extent of the seroma and if considerable and refractory to aspirations, an operation may be needed to remove the bursa.

A lump up to 8 months after surgery is not normal. You should go see your plastic surgeon who can either determine what the lump is, begin a work up (which may include ultrasound), or refer you to a general surgeon.

Without a physical examination, it is hard to tell what is going on. Best to follow up with your doctor for his evaluation and advice. Best of luck! Dean Vistnes.