"Our study shows that liposuction is associated with a very low complication rate, with major complications occurring in less than 1 in 1,000 patients," comments ASPS Member Surgeon John YS Kim of Northwestern University, Feinberg School of Medicine, Chicago. "It also calls into question the concept of simple absolute thresholds for lipoaspirate volume—the amount of liposuction that can be performed safely seems to depend in part on how much fat content a person begins with."

There's a long history of debate over the safe volume of fat tissue that can be removed by liposuction. Current ASPS guidelines define 5,000 milliliters (five liters) as "large-volume liposuction" potentially associated with a higher risk of complications. But the guidelines acknowledge there is no scientific data to support an absolute cutoff point.

Dr. Kim and colleagues analyzed data on more than 4,500 liposuction patients drawn from the ASPS's "Tracking Operations and Outcomes for Plastic Surgeons" (TOPS) database. They evaluated the relationship between liposuction volume and complication risk—including interactions with the patient's BMI.

The overall complication rate was 1.5 percent, with few serious complications and no deaths. By far, the most common complication was a fluid collection (seroma) requiring drainage. The average liposuction volume was about two liters.

Patients with complications had larger liposuction volumes—average 3.4 liters—and higher BMIs. Patients undergoing "large-volume" liposuction of more than five liters had a higher overall complication rate: 3.7 versus 1.1 percent. This resulted almost entirely from an increase in seromas.

There was also a significant interaction between liposuction volume and BMI: when patients with higher BMIs had a greater liposuction volume, the complication rate was actually somewhat lower.

"In other words, obese patients may tolerate larger lipoaspirate volumes without an increased risk of complications," the researchers write. In contrast, patients with lower BMIs experience a "more exponential increase in risk" at higher liposuction volumes. This relationship between a patient’s pre-existing fat content and "safe" liposuction volumes had not been previously shown.

Dr. Kim and colleagues introduced the concept of a "relative liposuction volume threshold" based on BMI. Dr. Kim and co-researcher Dr. Karol Gutowski emphasized that this provides a relative threshold where complications start to increase, but does not imply an absolute limit on liposuction volumes. Other considerations such as length of surgery, adjunct procedures, and the patient's overall health status are also important to consider when evaluating liposuction risk.

"Our risk assessment tool can further aid shared decision-making between the surgeon and patient by linking BMI and liposuction volumes," adds Dr. Kim.