Between 40 and 130 ml of lipoaspirate (ideally 100 ml) are processed at each time in the standard 225-ml device. To avoid cell damage, no air should be in the device during all procedural steps and the device should be prefilled with saline before beginning the processing. The aspirated fat should be always surrounded by a liquid environment: this is essential to obtain healthy smaller fat clusters instead of oil and adipose tissue debris. The first cluster reduction was obtained by pushing the aspirated fat from the syringe into the device and through the first size reduction filter while allowing the corresponding quantity of saline to exit towards the waste bag. The final Lipogems product is then collected into 10-ml syringes connected to the upper opening of the device. The final Lipogems product is now ready for the injection in the perianal fistula.