The technique established in this study proved to be efficient in terms of the simplicity of its approach. A technique similar to the presently described one is percutaneous endoscopic gastrostomy, performed in humans and described by Gauderer et al. in 1980, which has indications in cases of patients unable to eat normally for reasons such as neuropathies, congenital diseases, neoplasms, traumas, etc. The main advantages of both techniques are the possibility of gastrostomy without the need for laparotomy, avoiding further injuries to patients; less postoperative pain; and shorter surgical and anesthetic time.
Some minimally invasive techniques performed in the gastrointestinal tract of ruminants have been described, including laparoscopic abomasopexy, used to treat abomasum displacement, and laparoscopic abomasal cannulation [1, 19, 38].
Rumenoscopy is the visualization of the ruminal structures with an endoscope. It allows the cannulation of the rumen, as described in this study. It is believed that percutaneous rumenostomy by rumenoscopy can be performed without the use of general anesthesia, only with the use of sedation for chemical containment, plus simple locoregional anesthesia, meeting this procedure’s goals of less invasiveness and lower anesthetic risk [13, 14, 25].
The mean duration obtained for the rumenoscopy-guided rumenostomy procedure was 11.15 ± 0.7 min. Minimally invasive techniques tend to have less surgical time than conventional techniques. In the newly developed video-assisted rumenostomy technique, the time obtained was 13 ± 6.2 min [31], while in conventional techniques, the surgical time varies from 15 to 25 min [33] when performed in a surgical stage. In humans, percutaneous endoscopic gastrostomy was performed in 8 ± 3 min, while the open surgical gastrostomy technique had a mean duration of 35 ± 1.3 min [11].
It is important to highlight that the time in endosurgical techniques depends on the training and experience of the surgeon and the surgical team, as well as on the proper use of the devices to avoid complications and to ensure a good execution of the procedures [9, 21].
The decubitus used in this rumenoscopy technique was efficient, as well as that used in the laparoscopy rumenostomy procedure. In this same procedure, the 36-h fast, combined with the decubitus, allowed a good visualization and manipulation of the rumen, in addition to avoiding regurgitation and inhalation of rumen contents. However, although the percutaneous endoscopic rumenostomy has not yet been tested in live animals, it is believed that the rumenoscopy technique can be performed in standing animals [13, 14, 31].
The visualization of the structures and the possibility of performing the technique in neonate animals using the present study’s model have been confirmed. Further studies are also necessary to verify this technique’s feasibility in adult and larger animals, in which the presence of rumen content, ruminal motility, and larger organ size and length can be complicating factors.
The proposed model has some important points and limitations that require attention when it is eventually tested in living animals. The age of the corpses used, in which the rumen is not yet the main gastric compartment, is one of these factors. The size of the piece and the fact that it is a corpse imply that performing this technique and visualizing the ruminal structures are easier, despite the absence of the peristaltic movements, rumen content, and resistance of the animal to the endoscope.
Franz and Baumgartner, in 2002, used a 100-cm long endoscope for calves up to 7 months of age, and a 150-cm endoscope for animals between 7 months and 6 years of age. The endoscope used in the present study was 100 cm long, which can be a limiting factor for performing the technique in older and larger animals, as it may make it impossible to reach the desired site for cannulation.
Another factor that will need to be evaluated when this technique is tested in live animals is the need for rumenopexy, especially in older and larger animals, due to the weight of the rumen. In 2020, Griffin et al. described a new gastrostomy technique in canine models and highlighted the importance of gastropexy to help prevent complications such as leakage of the stomach contents, especially in dogs weighing more than 25 kg.
As already mentioned earlier, studies involving the cannulation of gastric chambers in ruminants are extremely necessary for animal experimentation, though the clinical need is also a reality [30, 38]. Some specific cases, such as studies on the mitigation of methane produced by ruminants, are extremely important scientific issues today [8, 23].
Thus, the proposed models are the most compatible, because conventional cannulas would interfere with the gas exchange of the rumen with the ambient air, due to cannula displacement, a relatively frequent event [35], as well as at the moment of opening the cannula. These problems were the factors that encouraged our team to develop an in vivo model of minimally invasive rumenostomy in sheep [31], since rumen puncture for many days would bring injury, cannula opening, and ambient air intake, and an oral probe would contaminate the sample with saliva. However, the model can also be executed by new proposed techniques, in simpler and more practical ways.
