In this study, Ta-IPAA results in improved pouch function and QoL compared to Tabd-IPAA at 12 month follow-up. Patients who underwent Ta-IPAA experienced better gastrointestinal function starting from 3 months postoperatively. At 1 month follow-up, functional results were worse than Tabd-IPAA. This might be explained by the use of the transanal platform with prolonged concentric stretching of the anal muscles fibers. However, this effect seems to be self-limiting and a full recovery of the sphincter function can be expected. (12, 13)
As consequence of the adaptation period during which the ileo-anal pouch becomes more compliant and begins to function and act as a reservoir, a constant and progressive improvement of pouch function was observed over time. (14) Both PFS and OS dropped significantly from month 1 to months 12 after surgery. For the reason discussed above, this improvement was more pronounced in the Ta-IPAA group (Δ PFS = 6.1 and Δ OS 3.8 points). Therefore, this is an aspect which deserves specific consideration during the preoperative counseling of patients scheduled for Ta-IPAA.
At 12 months follow-up, mean differences in OS and PFS between group still favored Ta-IPAA [1.5 (CI 0.2;2.8), and 1.3 (CI 1.3–3.9), respectively]. Moreover, better bowel function in Ta-IPAA resulted in better QoL. [Diff=-6.9 (CI -13.7;0.2)] This confirmed the findings of a previous multicentric comparative study which showed similar pouch function-related QoL between Ta- and Tabd-IPAA, 12 months after surgery, according to the Cleveland global quality of life (CGQL). Energy levels and QoL were significantly better after Ta-IPAA. However, individual components rather than global bowel function assessment were investigated and no difference was found in terms of stool frequency and major incontinence. (15) In contrast, the strength of this study is the comprehensive report of the gastrointestinal functional after pouch surgery by using two different tools (OS and PFS) whose reliability and reciprocal correlation has been previously demonstrated. (16) Results on QoL have to be interpreted cautiously, as the present study focused on functional outcomes (pouch function) and no validated QoL questionnaire was administered to patients. Furthermore, a limited correlation between both OS/PFS and the impact on social life has already been reported suggesting that on long-term follow-up pouch function does not necessarily correlate with QoL as result of patients’ lifestyle adaptation to their own specific bowel habits. (17, 18)
Better functional outcomes after Ta-IPAA might be explained by some key technical advantages compared to Tabd-IPAA. The transanal approach provides the surgeon with an optical control of the rectal cuff. (19) Transanal rectum transection avoids the risk linked to the conventional anterior approach such as oblique transection and multiple stapler firings. Appropriate length of rectal cuff is crucial in preventing occurrence of cuffitis and pouch evacuation problem. (20) Furthermore, the transanal approach allowed close rectal dissection. Although anterior rectal dissection according to the principle of total mesorectal excision (TME) is not essential in UC patients without dysplasia, this is still the preferred approach of many surgeons due to the avascularity of the dissection and the familiarity with a well-established oncological technique. (21) On the contrary, a transanal approach allows easily intramesorectal dissection along the rectal conduit, minimizing the risk of nerves injury and preserving the mesorectal fat which might be beneficial in limiting the burden of postoperative pelvic septic complications. (22) To date, ongoing inflammation as a result of the retained mesorectum has been postulated only in Crohn’s disease. (23)
All transanal procedures included in the present study have been performed during the first two years after the introduction of Ta-IPAA (2015) at our department. Nonetheless, the bias introduced by the learning curve seemed not to affect short-term outcomes (no conversion and comparable rate of anastomotic leakage) and corroborates even more the presented functional results.
Limitations of the study are related to its retrospectivity. A high percentage of patients had missing outcome information after 12 months, especially in the Ta-IPAA group. An exploratory analysis (results not shown) revealed that the missingness of functional scores at 12 months was not completely at random i.e. subjects with higher functional scores at earlier time points had a higher probability to have missing data at 12 months. Although taken into account in the statistical analysis using a likelihood approach, this remains a weakness of the study. Further, in this exploratory retrospective study, no correction for multiple testing was considered for the three outcomes at 12 months. Finally, no validated score for QoL was used and data on it should therefore interpreted with caution.