A mechanism for constructing a durable purse-string during transanal total mesorectal excision.

Abstract

The technique of transanal total mesorectal excision (taTME) using the transanal minimally invasive surgery (TAMIS) platform [1, 2] remains in the early phase of adoption [3], and important changes have been made which are part of the natural evolution process. Despite an enriched experience, we are collectively still in the 2b-‘Exploration’ step of the IDEAL framework described by McCulloch et al. [4], and changes to taTME methodology are likely to continue until the approach has been optimized. To date, efforts to solve technical problems have included the application of a valveless trocar system to minimize bellowing in the pelvis and to maintain visual field clarity [5, 6] and also the application of a drain to assist in ‘escorting’ the stapler spike though the pursestring center point [7] and the use of a hemorrhoidal stapler (with long anvil spike) to assist in creating a very low stapled anastomosis [8]. An important step of taTME with TAMIS is the application of the purse-string, which defines the distal margin and which must be properly constructed so that a durable seal is created and leakage of bowel contents eliminated. The current approach is imperfect because the suture is typically performed under direct vision or using TAMIS and laparoscopic suturing with the knots secured by hand tying or by use of a knot pusher. The limitation of these techniques is imprecision (particularly for more proximal purse-strings) and this could lead to disruption of the pursestring during taTME and thus an increased risk of bacterial contamination. This video demonstrates how the mechanics of a transanal hemorrhoidal dearterialization (THD) speculum can be used to create a durable purse-string [v]. The key is the preset depth of the THD mechanism that anchors each stitch at the proper depth ensuring adequacy. No Doppler is required, and rather than figure-of-eight suture that is performed with THD, the purse-string is constructed by constant rotation of the device in a counter-clockwise fashion. The device is removed, and the knot is secured manually. This approach borrows from the mechanical arrangement of THD device that anchors the nose of the needle driver in a way that automatically delivers the suture to the proper tissue depth. Hence, each purse-string stitch is accurately replicated. This mechanism then could be used to design a speculum similar to this that utilizes the needlenose cradle and window of the THD speculum. Such a speculum could be added to existing TAMIS kits or provided separately, and could also be constructed to be reusable. This would allow for a simplified, cost-effective method of manually ‘machining’ a purse-string suture during taTME.