Laser treatment for anal fistulas: what are the pitfalls?
Venue: Techniques in Coloproctology
Year: 2020

Laser treatment for fistula in ano, also known as FiLaCR (fistula laser closure) or LAFT (laser ablation of fistula tract) has gained increasing attention in the last decade. The procedure consists of delivering laser energy at 360deg within the lumen of fistulas by means of a radial fiber which is slowly withdrawn from the external orifice. Laser ablation is limited to the lumen of fistulas making the technique 'sphincter saving' Its main indication is the treatment of high fistulas and, in general, of all fistulas where more invasive treatments may impair anal continence. Since 2011, after a German group published the first pilot study  clinical results of this minimally invasive procedure were reported in a few papers, prompting growing interest in this novel technique in the scientific community. As for most procedures, the literature showed controversial results over the years. Following the first encouraging results  some studies reported a high percentage of failures [6 9] This raised some concerns and led to the consideration that the destiny of the procedure was similar to that of many others: the initial enthusiasm was followed by a high, yet unexpected, disappointing future at long term followups. However, a few considerations need to be stressed. First of all, the results of a few studies showed a variable percentage of success but longer follow ups were not necessarily associated with higher recurrence rate [4, 8] Interestingly, in most series, the failures after FiLaC were in the form of 'non healing' or persistence of the fistula tract rather than recurrence. Therefore, attention needs to be focused primarily on the efficacy of the procedure and not to failure in the long term like for other sphincter saving treatments (fibrin glue, plugs) Why success rates differ significantly between different studies may have several explanations and these need to be analyzed. The great variability in type, length and size of the fistulas treated may play a major role in affecting the success rate. The shrinkage of fistula tracts caused by laser depends on the wavelength and the amount of energy of the laser beam delivered within the tract. With the parameters used by most centers, the shrinking effect should successfully heal fistulas with a diameter of maximum 4 5 mm. There is no guarantee of efficiency for larger fistulas. This would explain some failures in a few studies. De Bonnechose et al.  in the current issue of Techniques in Coloproctology, reported fistula healing in 44.6% of patients. In this study, fistulas with a large internal orifice had only a 15% healing rate compared to 49% healing in fistulas with a narrow internal opening. However, the fistula diameter is difficult to measure. In the study by De Bonnechose, even the diameter of the internal orifice is subjectively measured, based on how tight the orifice is around the fistula probe [10] The size of internal orifice may have poor correlation with the diameter of the fistula tract. In our experience, we found that curettage and insertion of a silastic drain in the lumen of the fistula in a firststage operation as bridge to laser treatment (second stage, 12 weeks later) may induce the formation of fibrotic tissue, "modeling" the fistula around the draining loop. This process would help reach the optimal width and caliber (4 mm. making the fistulas more suitable for the following laser treatment. The length of the fistula tract may also play a role in influencing the success rate. In this regard, results in the literature are rather controversial. While some authors consider the length of the fistula the 'Achille's heel' of laser treatment [6] we have a different opinion based on our experience: the longer the fistula the better the shrinkage effect elicited by laser energy. This finding has been confirmed in a recent study  The concept is based on the assumption that the presence of a longer tract around the sphincters increases the P. Giamundo pgiamundo@gmail.com