MIEO: a micro-invasive endoscopic operation port system for transluminal interventions—an acute and survival porcine study

Although the hype on transluminal procedures has faded in recent years, the idea is still charming and many researchers worldwide continue to develop innovative concepts that will one day allow for less invasive, or better, less stressful interventions. Nowadays, researchers are no longer focusing on replacing conventional laparoscopic interventions but on developing new principles that offer real advantages to the current standard. In this regard, peroral endoscopic myotomy [1] and transanal total mesorectal excision [2] deserve notion as good examples to highlight the potential of transluminal surgery. Despite any future application, a safe and reliable technique to penetrate the natural orifice still represents one of the main obstacles and requires, particularly in the colon, technical precautions to prevent infection. Since this goal is difficult to achieve in a highly dynamic environment with continuous peristalsis and intestinal fluids passing, primary focus in past years was given to occlusion devices that block the entire intestinal lumen. Linke et al. in 2013 proposed a balloon occluder to be placed cephalad to the penetration site [3, 4] and which was tested against conventional laparoscopic cholecystectomy [5]. A similar technology was proposed by Du et al. [6]. The technique to enter the abdomen, however, has remained almost unchanged. While some groups chose direct endoscope penetration [7, 8], our group was the first to propose usage of a transluminal overtube [9] to penetrate the intestinal wall and establish a permanent gate to the abdominal wall. The so-called ISSA (innovative safe and sterile access) worked similarly to a laparoscopic trocar and to a certain extent was able to separate the endoscope from the intestinal lumen. However, moving the overtube in and out the peritoneal cavity always caused spillage of intestinal fluids into the abdomen. That is, why maybe Senft combined an identical overtube system with an intestinal occluder [3]. Also effective disinfection of the entry site deems essential to minimize the risk of contamination but is confined to simply washing out the intestine [10‐12]. This might be acceptable in the rectum where disinfecting solutions can directly be applied, but fails in the colon. Accordingly, peritoneal contamination is observed as a constant side effect of transcolonic surgery [13].

In summary, although certain goals for a universal transluminal access system have been achieved, key aspects such as a proper sealing of the entry site and improved disinfection are still unmet. With the MIEO, we aimed to develop a universal port system that can be used anywhere throughout the gastrointestinal tract and for any transluminal application, and that combines full flexibility for endoscopic manipulation with high level of sterility maintenance and safety. In this manuscript, we focus on the in vivo evaluation of the port system, while technical details and ex vivo studies will be published separately, as well as we did not intend to develop a new transluminal procedure.

Reducing the interventional trauma by promoting transluminal surgery still is highly attractive, although the hype on this kind of intervention has faded, if not completely disappeared over the last years. Notwithstanding, some studies and meta-analyses assume advantages for transluminal surgery concerning the postoperative pain [15‐17] and the cosmetic result while meeting overall complication and success rates of laparoscopic surgery. Still, the evaluation of transluminal techniques continues, e.g. for specimen retraction [18] or for gastroenterostomy [19] indicating a sustained belief in this method. However, human application is still limited and can maybe be attributed to three central aspects or, explicitly, the unavailability of suitable instruments [20, 21], missing indications, and unavailability of a universal and safe port system.

The safe and sterile access to the peritoneal cavity is an absolute requirement for transluminal surgery and for transcolonic surgery in special. According to Kantsevoy [22], different phases of a transluminal procedure have to be considered with the access phase, the intervention phase and the postoperative course being the most relevant. In other words, any access technique for transluminal surgery must prevent from contamination during the penetration of the intestinal wall, must seal the entrance site during the entire intervention, and finally must offer a highly reliable closure technique.

With the MIEO-Port we did not aim only to address all of the aforementioned aspects, but to develop a rather universal port system, that can be used anywhere along the gastrointestinal tract, irrespective if applied via the anus or mouth.

For contamination control, which by far is of higher relevance than universal applicability, two key innovations are featured by the MIEO-Port. First the reversible docking to the intestinal wall by suction that leads to separation and sealing of the penetration site. This principle to the best of our knowledge has not been described before and allowed in prior tests for intestinal attachment of the port with sufficient strength (> 2 N) and with hermetically sealing the docking site. The principle worked reliably well during the ex vivo tests and also during the presented in vivo evaluation; however, it was associated with tiny haemorrhages at the entry site caused by vacuum suction. As we could not exclude post-fixation necrosis or fistulas due to ischemia or mechanical alterations at the docking site, the evaluation of the intestinal wall surrounding the entrance site was of special interest. Following observation over 10 days and after a median fixation time with continuous suction of more than 30 min, fortunately, we could not identify any related complications, nor did we register any remnant of these spots, even after careful exploration. The intestine was healthy and intact without adhesions and even from the inside no scars or alterations were noticed. Accordingly, but limited by the small study size and the short duration of the chosen intervention, we assume the principle of coupling by vacuum suction as reliable.

However, in one case a dislocation of the MIEO-Port had to be observed during withdrawal of the endoscope. We really can not reason this, but assume that the extensive manipulations after retroperitoneal incision might have resulted in forces which exceeded our laboratory specifications. As in any other experiment with peritoneal access, as well as in all ex vivo tests the port system had remained fixed to the intestinal wall we believe this to be the best explanation. To prevent from such adverse events during later clinical application, we propose usage of a sensor controlled suction pump that registers leakage by increased air flow to signal any dislocation or incomplete docking. Nevertheless, further studies and ex vivo tests are warranted to ascertain the required fixation force for transluminal manipulations, which we assumed to be equal or higher than 2 N according to prior tests.

The second innovative feature of the MIEO-Port is the local decontamination by jetting the intestinal surface with a disinfectant, a principle well known from soft tissue infections [23]. Although we did not evaluate on this in a comprehensive comparative setting, we believe, according to the existing ex vivo tests local jetting with use of Octenidine to be superior to the traditional enemas and irrigation methods [11, 13]. In these tests and in comparison with water, Polyiodvidone and Polyhexanide, only the final procedural method was capable to reduce the intestinal bacterial load to an acceptable low level or zero. These results correspond to others, for example Müller, who noticed a remaining and comparatively high contamination rate of the mucosal surface and translocation of bacteria into the abdominal cavity after he had applied Polyiodvidone enemas [24]. We also believe our technique to be better for other reasons. First, it guarantees by principle the direct and local application of the disinfectant at the penetration site. Second, the straight application of the disinfectant via tubes maintains the original concentration of the applied agent, keeping its biochemical effectiveness. And third, the intestinal surface is cleansed under direct visual control, so the disinfection process can be continued until the intestinal surface visually appears clean. Again, we did not comprehensively evaluate on this item; however, we would rate this conclusion as reproducible and logically consistent. Nevertheless, our investigation showed results which did not convince completely as contamination was registered even after careful disinfection. During post-mortem examination in two animals, we could not register any infections, neither by inspection nor by smear examination and microbiologic testing, whereas in another two animals, minor contamination was identified but only locally. It is unclear whether these positive swabs resulted from the intervention itself, from the postoperative healing process, or maybe from a minor contamination prior to the application of the OTS Clip but would rate this minor contamination to be within the acceptable limit. These results need to be separated from the obvious contamination in the first animal, which we assume to have resulted from the unintended detachment of the endoscope. With the loose endoscope, an unrealized contamination of the endoscope shaft and internal surface of the port might have occurred, which was then translocated to the abdomen.

An ideal access technique finally claims for reliable closure of the penetration site. As we were unable to reuse the proven suture technique formerly chosen for the ISSA [9, 25, 26], we had to find an alternative resilient technique, which was the OTSC (Ovesco, Tübingen, Germany). It is well evaluated for closure of intended [27, 28] and unintended [29, 30] perforations and proved reliability in numerous publications. Furthermore, we believe that the OTSC can be modified for integration into the MIEO-Port, for example if imposed to the head component, which would then enable immediate closure of the entrance. Fortunately, the OTSC again worked perfectly well resulting in the intended safe and reliable closure of the penetration site which was supported by guidance by the docking marks.

Despite being developed as a port system for transluminal surgery, we also evaluated the MIEO-Port for controlled endoscopic mucosectomy. Although our test was unable to prove this suitability, we assume in specific cases and with a suitable pathology the port could become enabling as by supporting underwater dissection or by providing a gauge pressure to control bleeding, as it is known from laparoscopy. These applications are only speculative and require further investigations and maybe also further modifications of the port system. Another potential field of use we suppose could be postoperative complications, for example after failed colon resections, where the MIEO-Port could ease necrosectomy and cleansing of the defect and facilitate controlled irrigation. As a fact, with this study we only focused on the main principle of the MIEO-Port and on its usability during transluminal interventions, but not on the development of a new procedure, so further studies are required.

Admittedly, the presented study has several limitations with the small sample size being the most relevant one. The study design is non-comparative and only focuses on transluminal peritoneoscopies and one cholecystectomy, thus on minor surgeries. As we had to observe one dislocation of the port in one animal after extensive manipulation, further studies must prove the reliability of the port system also for longer and more complex interventions. Although evaluated on in prior ex vivo tests, the disinfection principle likewise requires refinement and definition of a standardized protocol. Accordingly, the presented results are only primary and warrant further studies and optimization of the MIEO-Port.