Human cadavers as an experimental model for esophageal surgery

On the suitability of Thiel cadavers for natural orifice transluminal endoscopic surgery (NOTES): surgical training, feasibility studies, and anatomical education

BACKGROUND

Surgical training in virtual, animal and cadaver models is essential for minimally invasive surgery. Thiel cadavers are suitable for laparoscopy, but there are few data about the use of embalmed (Tutsch method) and slightly embalmed (Thiel method) cadavers in procedures of Natural Orifice Transluminal Endoscopic Surgery (NOTES), which are usually developed and learned on swine models and fresh frozen cadavers. The aim of this study was thus to assess the use of these cadavers for NOTES approaches.

METHODS

The following surgical procedures were evaluated: transanal total mesorectal excision (four cadavers: one Tutsch, two Thiel, one fresh frozen), transanal ileorectal bypass (five cadavers: one Tutsch, three Thiel, one fresh frozen), and transvaginal appendectomy (two Tutsch cadaver).

RESULTS

The Thiel method ensured tissue flexibility and consistency suitable for performing the above surgical procedures with good results and without complications, with only a small increase in rigidity with respect to fresh specimens. Cadavers embalmed with higher formalin concentrations (Tutsch method) were more difficult to use, due to high tissue rigidity and resistance of the abdominal wall to pneumoperitoneum, although NOTES accesses were possible.

CONCLUSIONS

Thiel cadavers are suitable for transanal/transrectal and transvaginal NOTES approaches, for training surgical residents/specialists and also for surgical research. In minimally invasive surgery (and particularly in NOTES), integration between cadaver (fresh frozen and/or Thiel) and animal models would represent the gold standard, allowing guaranteed knowledge of and respect for human surgical anatomy and correct management of surgery on living subjects. NOTES approaches to human cadavers may also be proposed for the anatomical education of medical students.

Thoracotomy versus transhiatal esophageal dissection: which is the best surgical approach to short esophagus?

PURPOSE

To evaluate different approaches performed to obtain a more significant esophageal length.

METHODS

An experimental model using 28 cadavers was conceived. Randomized groups: Group A (n=10) underwent laparotomic transhiatal approach; Group B (n=9) which differed from the first in the conduction of a wide phrenotomy and Group C (n=9) esophageal dissection was performed through a left anterolateral thoracotomy.

RESULTS

Final length variations for Group A were 2.12cm and 3.29cm and for Group B 3.24 cm and 3.66cm, without and with esophageal traction, respectively. In Group C length gain observed was 3.81 cm. The mediastinal dissections conducted through the hiatus was considered the procedure that produced the better esophageal mobilization, and the association of wide phrenotomy significantly improved the results.

CONCLUSION

The mediastinal dissection was the most effective to improving gain in abdominal esophagus. When toracotomy and laparotomy were compared, no significant differences were observed in the outcome.

Gastric fundus tension before and after division of the short gastric vessels in a cadaveric model of fundoplication

Short gastric vessels (SGV) division is a controversial topic in antireflux surgery. Some surgeons do not divide the SGV routinely to perform a fundoplication; however, excessive tension of the gastric fundus (GF) forces this procedure necessary in some cases. This study aims to evaluate in a cadaveric model of Nissen fundoplication: (i) the correlation of GF tension with anatomic parameters; and (ii) the effect of SGV division on GF tension. In total, 23 fresh cadavers (18 men, mean age 62 years) were studied. The abdominal esophagus was dissected, and the GF transposed to a limit of 3 cm to the right border of the esophagus. A dynamometer was attached to the GF and the tension recorded. Cadavers were grouped according to the presence or absence of tension. SGV were divided and GF tension measured again. The presence or absence of initial GF tension was correlated to: (i) number of SGV; (ii) length of the GF; (iii) distance between His angle and the first SGV; and (iv) size of the spleen. The mean GF pressure was 0.5 N +/- 1.0 (0-2.5) before SGV division and 0.1 N +/- 0.3 (0-1.5) after SGV division (P= 0.002). Initial tension was absent in 12 (52.2%) cases. GF tension did not correlate with any of the anatomic parameters. Our results show that: (i) GF tension does not correlate with anatomic parameters; and (ii) SGV division affects GF tension significantly.

The effect of azygos vein preservation on mediastinal lymph node harvesting in thoracic esophagolymphadenectomy

The standard surgical procedure for esophageal cancer is transthoracic esophagectomy with en bloc resection of the azygos vein, thoracic duct and mediastinal lymph nodes. To reduce morbidity of esophago-lymphadenectomy, minimally invasive techniques are increasingly being applied. In (robot-assisted) thoracoscopic esophagolymphadenectomy, the azygos vein is generally left in place, as the scopic ligation of the numerous intercostal veins is technically difficult and time-consuming. This could affect the extent of mediastinal lymph node dissection. Therefore, in this study, the effect of azygos vein preservation during thoracic esophagectomy on mediastinal lymph node harvesting was assessed. In 15 human cadavers, a right-sided thoracotomy was performed, followed by esophagectomy with mediastinal lymph node dissection after ligation of the azygos arch (representing the situation in robot-assisted thoracoscopic esophagolymphadenectomy). Subsequently, the remaining azygos vein with surrounding tissue was resected. The number of lymph nodes in both specimens was determined. A mean of 17.3 (95% Poisson CI 15.3-19.6) lymph nodes was dissected en bloc with the esophagus, and 0.67 (95% Poisson CI 0.32-1.23) around the separately resected azygos vein. The additional azygos vein resection did not add to the number of lymph nodes dissected in 60% (9/15) of cadavers. In conclusion, the extent of mediastinal lymph node dissection was not substantially affected by leaving the azygos vein in situ . Time-sparing azygos vein preservation in (robot-assisted) thoracoscopic esophagolymphadenectomy may therefore be considered justified.

Vagal integrity in vagal-sparing esophagectomy: a cadaveric study

Esophagectomy is associated with a significant number of complications, some of them related to the concomitant vagotomy. The vagal-sparing esophagectomy is an attractive alternative to the conventional procedure; however, few clinical series have attested the integrity of the vagi nerves after esophagectomy. The surgical anatomy of the vagus in the mediastinum has received little interest as well. The anatomy of the vagus was studied in 30 fresh cadavers. Twenty cadavers were submitted to a vagal-sparing esophagectomy, and after the procedure, anatomical vagal integrity was evaluated. Concerning the anatomy of the vagus, one or more vagal trunks were present in all cases. Four patterns were identified: Type I, two distinct trunks without communicating branches, present in eight (26.7%) cases; Type II, two distinct trunks with communicating branches, present in 17 (56.7%) cases; Type III, one or more bifurcated trunks, present in four (13.3%) cases; and Type IV, crossing trunks, present in one (3.3%) case. Regarding the esophagectomy, operative accidents were not noticed; in five cases, there was incomplete removal of the muscular layer of the esophagus. In all cases vagi nerves were preserved. The vagus is preserved in a cadaveric model of the vagal sparing esophagectomy, irrespective of the anatomy of the vagus in the mediastinum.

[Experimental models in research]

The purpose of this study is to collect the main classifications of experimental research models and their possible applications in experimental research. Literature search was done using the most important data bank available on the internet (PUBMED, MEDLINE, SCIELO, LILACS, COCHRANE). A compilation of the experimental studies developed at the Plastic Surgery Post Graduate Program of the Federal University of São Paulo/Paulista School of Medicine was also done. Animals models were classified regarding sanitary and genotypical status. The understanding of the main classifications of the research experimental models is essential to improve and confirm procedures and techniques already described as well as the development of new ones.

Efficacy of mediastinal lymphadenectomy in transhiatal esophagectomy with and without diaphragm opening: a cadaveric study

Transhiatal esophagectomy (THE) is believed to induce a lower morbidity and mortality compared with transthoracic esophagectomy, but to be inefficient in performing mediastinal lymphadenectomy. Some surgeons are convinced that lymphadenectomy of the lower mediastinum in THE and transthoracic esophagectomy are equivalent. To test this, the authors performed THE in 20 cadavers (10 with and 10 without diaphragm opening). The number of lymph nodes resected with the esophagus and dissected through the hiatus was counted. After THE, the thorax was opened and the number of residual lymph nodes was evaluated. Complications were also assessed. The results show that lymphadenectomy in THE is incomplete in the lower mediastinum and not possible in the upper mediastinum; comparing THE with and without diaphragm opening, the first permits resection of a superior number of lymph nodes with the esophagus and dissection of a higher number of nodes through the hiatus. It is concluded that THE does not provide an effective mediastinal lymphadenectomy.