glue and saline solution (placebo) injection. At 1-year follow-up, the healing rate was as follows: Group A 57.1%, Group B 52.4%, and Group C 37.3%. In each group, IO was always closed.

At least, Dozois et al. (2019) reported a phase I clinical trial about the use of autologous mesenchymal stem cell-coated fistula plug in patients with trans­phincteric cryptoglandular fistulas. It is a two-step procedure based on lipo­aspiration and then a creation of the novel bioactive plug. At 6 months follow-up, three patients (20%) showed a complete healing while eight patients (53.3%) had only partial healing.

Moreover, the postoperative impaired anal continence rate may be not negligible, and it raises up to 53% after laying open an intersphincteric or transphincteric fistula (Lunniss et al. 1994).

Unfortunately, there are no clear guidelines for MSCs use in surgical fields. In particular, for digestive tract whose diseases are generally well localized, the suggested application of MSCs is through a local injection (instead of systemic use as for systemic diseases) thus minimizing the side-effects keeping MSCs directly in contact with the injured tissue. Moreover, there is no consensus about the procedure and its surgical steps as how to inject the cells (needle size, speed, concentration, and volume amount) to achieve the maximal beneficial effect (Georgiev-Hristov et al. 2018).

the number of procedures was linked to the complications occurrence and its rate increase. They range from minor complications such as seroma, edema, hematoma with minor bleeding, and local pain to more important, even life-threatening, compli­cations as pulmonary embolism, pneumothorax, and bowel perforation, occurring also in death in rare cases. There are some conditions considered as risk factors: thin abdominal wall, diastasis of the rectus abdominis muscles, abdominal distension that increases the abdominal convexity, umbilical or ventral hernia especially in those overweight patients in which they may be clinically misdiagnosed, and history of abdominal surgery with fixed scar. To prevent complications, the authors learned the lesson from plastic surgeons (Taha and Tahseen 2020; Zakine et al. 2015)and accurately evaluated the abdomen with physical examination to detect hernias or wall weakness. In case of risk factors, a preoperative abdominal ultrasound is performed. In addition, the procedure is performed carefully harvesting fat tissue from the superficial and deep subcutaneous fat without abrupt gestures always checking the cannula orientation and its tip. At last, patients are evaluated 3–5h after the procedure maintaining the compressive bandage and then reexamined on the first postoperative day before the discharge just after bandage removal. The only few cases of minor abdominal wall hematoma occurred in the authors’ series and were treated conservatively with topical eparine-like ointment administration. Hence, lipo­aspiration is an easy and fairly fast procedure to collect the amount of adipose tissue necessary to perform the surgical procedure for anal fistula, but it needs to be carried out with care being aware of possible consequences so that they can be prevented and eventually early identified and treated.