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__Abstract__ Colorectal surgery is an important aspect of our current health system, due to the high incidence of colorectal cancer combined with an ageing population, improved long-term outcomes after colorectal surgery, and the perfectioning of the operative and postoperative aspects through laparoscopy and enhanced recovery programs. However, postoperative complications painfully remain, despite efforts of amelioration of perioperative care. Research for molecular pathways and non-surgical treatment modalities of colorectal cancer and inflammatory bowel disease is rising in importance, however the improvement of quality and safety of colorectal surgery should remain and become ever more a key element for all colorectal surgeons. This thesis aims to add to this improvement.

Background: Adequate working space is a prerequisite for safe and efficient minimal access surgery. No objective data exist in literature about the effect of mechanical bowel preparation (MBP) on working space in laparoscopic surgery. We objectively measured this effect with computed tomography in a porcine laparoscopy model. Methods: Using standardized anesthesia, twelve 20-kg pigs without MBP and eight 20-kg pigs with MBP were studied with computed tomography at intra-abdominal pressure (IAP) levels of 0, 5, 10, and 15 mmHg. Volumes and dimensions of the pneumoperitoneum were measured on reconstructed CT images and compared between the pigs with and those without MBP. Results: A reproducible and statistically significant increase of approximately 500 ml in pneumoperitoneum volume was found in the MBP group at all levels of IAP. This represents a 43 % relative increase at a pneumoperitoneum pressure of 5 mmHg, 21 % at IAP 10 mmHg, and 18 % at IAP 15 mmHg. Peak inspiratory pressure was lower at IAP 0 and 5 mmHg in the MBP group. Anteroposterior diameter in the group with MBP was lower at 0 mmHg, but abdominal dimensions were similar in both groups at all other IAPs. This shows that the gain in working space is due to a diminished volume of the intra-abdominal content and not to compression or displacement of the bowel. Conclusions: MBP increases working space by reducing bowel content. Especially at low intra-abdominal working pressures, the increase in working space associated with MBP could represent an important benefit in challenging laparoscopic surgery.

Many different techniques of colorectal anastomosis have been described in search of the technique with the lowest incidence of anastomotic leak. A systematic review of leak rates of techniques of hand-sewn colorectal anastomosis was conducted to provide a guideline for surgical residents and promote standardization of its technique. Clinical and experimental articles on colorectal anastomotic techniques and

Background: Mechanical bowel preparation (MBP) has been shown to have no influence on the incidence

Background: With an increasing percentage of colorectal resections performed laparoscopically nowadays, there is more emphasis on training "before the job" on operative skills, including the comprehension of specific laparoscopic surgical anatomy. As integration of technical skills with correct interpretation of the anatomical image must be incorporated in laparoscopic training, a human specimen training model with special emphasis on surgical anatomy was developed. Methods: The new embalming method Anubifix ™ combines long-term high-quality embalming of human bodies with almost normal flexibility and plasticity, and the body can be kept operational as long as conventionally embalmed human specimens. A colorectal training model was created in a specimen in which anatomical landmarks of colorectal anatomy were permanently colored to explore laparoscopic colorectal anatomy in a skills training setting. Airtight closure of the abdominal wall permits the creation of pneumoperitoneum. Residents were asked to test the model by mobilizing the small and large bowels and expose the central vessels and ureters. Afterward they were asked to fill out an eight-item questionnaire about the model. Results: Eleven surgical residents in their first and second year of training participated. Responses to the questionnaire showed that a majority of residents considered the model to be representative of the real situation and superior to animal models or virtual reality simulators, and helped to improve the knowledge of three-dimensional anatomy and laparoscopic skills. Conclusion The new training model for laparoscopic colorectal: surgery proved to be a high-quality tool, concentrating on laparoscopic colorectal anatomy in a skills training setting. We believe it may be a valuable adjunct to residency training programs based on the principle of "training

Background: Adhesions follow abdominal surgery with an incidence as high as 95%, resulting in invalidating complications such as bowel obstruction, female infertility, and chronic pain. Searches have been performed for a safe and effective adhesion barrier; however, such barriers have impaired anastomotic site healing. The primary aim of this study was to investigate the effect of a new adhesion barrier, polyvinyl alcohol gel, on healing of colonic anastomoses using a rat model. Methods: Thirty-two Wistar rats were divided in two groups. In all animals, an anastomosis was constructed in the ascending colon. The first group received no adhesion barrier, whereas in the second group, 2mL of polyvinyl alcohol gel (A-Part Gel®; Aesculap AG, Tuttlingen, Germany) was applied circularly around the anastomosis. All animals were sacrificed on the seventh post-operative day, and the abdomen was inspected for signs of anastomotic leakage. The anastomotic bursting pressure, the adhesions around the anastomosis, and the collagen content of the excised anastomosis were measured. Results: No significant differences were observed between the two groups in the incidence of anastomotic leakage, the anastomotic bursting pressure (p=0.08), or the collagen concentration (p=0.91). No significant reduction in amount of adhesions was observed in the rats receiving polyvinyl alcohol gel. Conclusions: This experimental study showed no significant differences in anastomotic leakage, anastomotic bursting pressure, or collagen content of the anastomosis when using the adhesion barrier polyvinyl alcohol around colonic anastomoses. The barrier did not prevent adhesion formation.

Purpose: Both "high tie" (HT) and "low tie" (LT) are well-known strategies in rectal surgery. The aim of this study was to compare colonic perfusion after HT to colonic perfusion after LT. Methods: Patients undergoing rectal resection for malignancy were included. Colonic perfusion was measured with laser Doppler flowmetry, immediately after laparotomy on the antimesenterial side of the colon segment that was to become the afferent loop (measurement A). This measurement was repeated after rectal resection (measurement B). The blood flow ratios (B/A) were compared between the HT group and the LT group. Results: Blood flow was measured in 33 patients, 16 undergoing HT and 17 undergoing LT. Colonic blood flow slightly decreased in the HT group whereas the flow increased in the LT group. The blood flow ratio was significantly higher in the LT group (1.48 vs. 0.91; p = 0.04), independent of the blood pressure. Conclusion: This study shows the blood flow ratio to be higher in the LT group. This suggests that anastomoses may benefit from better perfusion when LT is performed.