Choosing the best animal species to mimic clinical colon anastomotic leakage in humans: a qualitative systematic review

Postoperative ileus-Establishing a porcine model

BACKGROUND

Postoperative ileus (POI), characterized by absent gastrointestinal motility, is a frequent complication following major abdominal surgery, with no current effective treatment possibilities. For further research in the treatment of this condition, we aimed to establish a porcine model of POI.

METHODS

A total of 12 Landrace pigs, weighing 60 kg, were included. Five animals were used as pilots to establish the surgical procedure, five animals received the same reproducible surgical procedure developed in the pilot experiments, while two animals were used as control. The primary endpoint was number of days to first stool. Intestinal motility was monitored using the SmartPill system.

KEY RESULTS

Four of the five pigs who underwent the final surgical procedure passed first stool on the third postoperative day (POD), and one passed first stool on the fifth POD. SmartPill data showed retention of the capsule in the stomach in four of five pigs with usable traces.

CONCLUSION AND INFERENCES

An experimental porcine model of POI was established, forming the basis for future studies in POI.

Peritoneal fluid indocyanine green test for diagnosis of gut leakage in anastomotic leakage rats and colorectal surgery patients

BACKGROUND

Application of indocyanine green (ICG) fluorescence has led to new developments in gastrointestinal surgery. However, little is known about the use of ICG for the diagnosis of postoperative gut leakage (GL). In addition, there is a lack of rapid and intuitive methods to definitively diagnose postoperative GL.

AIM

To investigate the effect of ICG in the diagnosis of anastomotic leakage in a surgical rat GL model and evaluate its diagnostic value in colorectal surgery patients.

METHODS

Sixteen rats were divided into two groups: GL group (n = 8) and sham group (n = 8). Approximately 0.5 mL of ICG (2.5 mg/mL) was intravenously injected postoperatively. The peritoneal fluid was collected for the fluorescence test at 24 and 48 h. Six patients with rectal cancer who had undergone laparoscopic rectal cancer resection plus enterostomies were injected with 10 mL of ICG (2.5 mg/mL) on postoperative day 1. Their ostomy fluids were collected 24 h after ICG injection to identify the possibility of the ICG excreting from the peripheral veins to the enterostomy stoma. Participants who had undergone colectomy or rectal cancer resection were enrolled in the diagnostic test. The peritoneal fluids from drainage were collected 24 h after ICG injection. The ICG fluorescence test was conducted using OptoMedic endoscopy along with a near-infrared fluorescent imaging system.

RESULTS

The peritoneal fluids from the GL group showed ICG-dependent green fluorescence in contrast to the sham group. Six samples of ostomy fluids showed green fluorescence, indicating the possibility of ICG excreting from the peripheral veins to the enterostomy stoma in patients. The peritoneal fluid ICG test exhibited a sensitivity of 100% and a specificity of 83.3% for the diagnosis of GL. The positive predictive value was 71.4%, while the negative predictive value was 100%. The likelihood ratios were 6.0 for a positive test result and 0 for a negative result.

CONCLUSION

The postoperative ICG test in a drainage tube is a valuable and simple technique for the diagnosis of GL. Hence, it should be employed in clinical settings in patients with suspected GL.

Experimental models of high-risk bowel anastomosis in rats: A systematic review

BACKGROUND

Anastomotic leaks remain one of the most dreaded complications in gastrointestinal surgery causing significant morbidity, that negatively affect the patients' quality of life. Experimental studies play an important role in understanding the pathophysiological background of anastomotic healing and there are still many fields that require further investigation. Knowledge drawn from these studies can lead to interventions or techniques that can reduce the risk of anastomotic leak in patients with high-risk features. Despite the advances in experimental protocols and techniques, designing a high-quality study is still challenging for the investigators as there is a plethora of different models used.

AIM

To review current state of the art for experimental protocols in high-risk anastomosis in rats.

METHODS

This systematic review was performed according to The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. To identify eligible studies, a comprehensive literature search was performed in the electronic databases PubMed (MEDLINE) and Scopus, covering the period from conception until 18 October 2023.

RESULTS

From our search strategy 102 studies were included and were categorized based on the mechanism used to create a high-risk anastomosis. Methods of assessing anastomotic healing were extracted and were individually appraised.

CONCLUSION

Anastomotic healing studies have evolved over the last decades, but the findings are yet to be translated into human studies. There is a need for high-quality, well-designed studies that will help to the better understanding of the pathophysiology of anastomotic healing and the effects of various interventions.

The colonoscopic vacuum model-simulating biomechanical restrictions to provide a realistic colonoscopy training environment

INTRODUCTION

Practicing endoscopic procedures is fundamental for the education of clinicians and the benefit of patients. Despite a diverse variety of model types, there is no system simulating anatomical restrictions and variations in a flexible and atraumatic way. Our goal was to develop and validate a new modelling approach for adhesion forces between colon and abdominal wall.

METHODS

An inlay for a standard mechanical trainer was designed and 3D printed. Colon specimens were fixed to the inlay along colon ascendens (CA) and colon descendens (CD) by a vacuum. Our system, which we refer to as Colonoscopy Vacuum Model (CoVaMo), was validated with 11 test persons with varying level of expertise. Each performed one colonoscopy and one polypectomy in the CoVaMo and in the Endoscopic Laparoscopic Interdisciplinary Training Entity (ELITE). Achieved adhesion forces, times required to fulfill different tasks endoscopically and a questionnaire, assessing proximity to reality, were recorded.

RESULTS

Mean adhesion forces of 37 ± 7 N at the CA and 30 ± 15 N at the CD were achieved. Test subjects considered CoVaMo more realistic than ELITE concerning endoscope handling and the overall anatomy. Participants needed statistically significantly more time to maneuver from anus to flexura sinistra in CoVaMo (377 s ± 244 s) than in ELITE (58 s ± 49 s).

CONCLUSION

We developed a training environment enabling anatomically and procedural realistic colonoscopy training requiring participants to handle all endoscope features in parallel. Fixation forces compare to forces needed to tear pig colon off the mesentery. Workflow and inlay can be adapted to any arbitrary ex vivo simulator.

Randomized experimental study of two novel techniques for transanal repair of dehiscent low rectal anastomosis

BACKGROUND

Anastomotic leak after low anterior rectal resection is a dreadful complication. Early diagnosis, prompt management of sepsis followed by closure of anastomotic defect may increase chances of anastomotic salvage. In this randomized experimental study, we evaluated two different methods of trans-anal anastomotic repair.

METHODS

A model of anastomotic leak was created in 42 male pigs. Laparoscopic low anterior resection was performed with anastomosis created using a circular stapler with half of the staples removed. Two days later, animals were randomized into a TAMIS (trans-anal minimally invasive surgery) repair, endoscopic suture (ENDO) or control group with no treatment (CONTROL). Signs of intraabdominal infection (IAI), macroscopic anastomotic healing and burst tests were evaluated to assess closure quality after animals were sacrificed on the ninth postoperative day.

RESULTS

Closure was technically feasible in all 28 animals. Two animals had to be euthanized due to progressive sepsis at four and five days after endoscopic closure. Healed anastomosis with no visible defect was observed in 10/14 and 11/14 animals in TAMIS and ENDO groups, respectively, versus 2/14 in CONTROL (p < 0.05). Overall IAI rate was significantly lower in TAMIS (4/14; p = 0.006) and ENDO (5/14; p = 0.018) compared to CONTROL (12/14). Burst tests confirmed sealed closure in healed anastomosis with a median failure pressure of 190 (110-300) mmHg in TAMIS and 200 (100-300) mmHg in ENDO group (p = 0.644).

CONCLUSION

In this randomized experimental study, we found that both evaluated techniques are effective in early repair of dehiscent colorectal anastomosis with a high healing rate.

Stem cell therapy applied for digestive anastomosis: Current state and future perspectives

BACKGROUND

Digestive tract resections are usually followed by an anastomosis. Anastomotic leakage, normally due to failed healing, is the most feared complication in digestive surgery because it is associated with high morbidity and mortality. Despite technical and technological advances and focused research, its rates have remained almost unchanged the last decades. In the last two decades, stem cells (SCs) have been shown to enhance healing in animal and human studies; hence, SCs have emerged since 2008 as an alternative to improve anastomoses outcomes.

AIM

To summarise the published knowledge of SC utilisation as a preventative tool for hollow digestive viscera anastomotic or suture leaks.

METHODS

PubMed, Science Direct, Scopus and Cochrane searches were performed using the key words "anastomosis", "colorectal/colonic anastomoses", "anastomotic leak", "stem cells", "progenitor cells", "cellular therapy" and "cell therapy" in order to identify relevant articles published in English and Spanish during the years of 2000 to 2021. Studies employing SCs, performing digestive anastomoses in hollow viscera or digestive perforation sutures and monitoring healing were finally included. Reference lists from the selected articles were reviewed to identify additional pertinent articles.Given the great variability in the study designs, anastomotic models, interventions (SCs, doses and vehicles) and outcome measures, performing a reliable meta-analysis was considered impossible, so we present the studies, their results and limitations.

RESULTS

Eighteen preclinical studies and three review papers were identified; no clinical studies have been published and there are no registered clinical trials. Experimental studies, mainly in rat and porcine models and occasionally in very adverse conditions such as ischaemia or colitis, have been demonstrated SCs as safe and have shown some encouraging morphological, functional and even clinical results. Mesenchymal SCs are mostly employed, and delivery routes are mainly local injections and cell sheets followed by biosutures (sutures coated by SCs) or purely topical. As potential weaknesses, animal models need to be improved to make them more comparable and equivalent to clinical practice, and the SC isolation processes need to be standardised. There is notable heterogeneity in the studies, making them difficult to compare. Further investigations are needed to establish the indications, the administration system, potential adjuvants, the final efficacy and to confirm safety and exclude definitively oncological concerns.

CONCLUSION

The future role of SC therapy to induce healing processes in digestive anastomoses/sutures still needs to be determined and seems to be currently far from clinical use.

Design of a force-measuring setup for colorectal compression anastomosis and first ex-vivo results

Purpose

The introduction of novel endoscopic instruments is essential to reduce trauma in visceral surgery. However, endoscopic device development is hampered by challenges in respecting the dimensional restrictions, due to the narrow access route, and by achieving adequate force transmission. As the overall goal of our research is the development of a patient adaptable, endoscopic anastomosis manipulator, biomechanical and size-related characterization of gastrointestinal organs are needed to determine technical requirements and thresholds to define functional design and load-compatible dimensioning of devices.

Methods

We built an experimental setup to measure colon tissue compression piercing forces. We tested 54 parameter sets, including variations of three tissue fixation configurations, three piercing body configurations (four, eight, twelve spikes) and insertion trajectories of constant velocities (5 mms⁻¹, 10 mms⁻¹,15 mms⁻¹) and constant accelerations (5 mms⁻², 10 mms⁻², 15 mms⁻²) each in 5 samples. Furthermore, anatomical parameters (lumen diameter, tissue thickness) were recorded.

Results

There was no statistically significant difference in insertion forces neither between the trajectory groups, nor for variation of tissue fixation configurations. However, we observed a statistically significant increase in insertion forces for increasing number of spikes. The maximum mean peak forces for four, eight and twelve spikes were 6.4 ± 1.5 N, 13.6 ± 1.4 N and 21.7 ± 5.8 N, respectively. The 5th percentile of specimen lumen diameters and pierced tissue thickness were 24.1 mm and 2.8 mm, and the 95th percentiles 40.1 mm and 4.8 mm, respectively.

Conclusion

The setup enabled reliable biomechanical characterization of colon material, on the base of which design specifications for an endoscopic anastomosis device were derived. The axial implant closure unit must enable axial force transmission of at least 28 N (22 ± 6 N). Implant and applicator diameters must cover a range between 24 and 40 mm, and the implant gap, compressing anastomosed tissue, between 2 and 5 mm.

Intestinal anastomotic healing models during experimental colitis

BACKGROUND

Anastomotic leakage represents a major complication following resections in colorectal surgery. Among others, intestinal inflammation such as in inflammatory bowel disease is a significant risk factor for disturbed anastomotic healing. Despite technical advancements and several decades of focused research, the underlying mechanisms remain incompletely understood. Animal experiments will remain the backbone of this research in the near future. Here, instructions on a standardized and reproducible murine model of preoperative colitis and colorectal anastomosis formation are provided to amplify research on anastomotic healing during inflammatory disease.

METHODS

We demonstrate the combination of experimental colitis and colorectal anastomosis formation in a mouse model. The model allows for monitoring of anastomotic healing during inflammatory disease through functional outcomes, clinical scores, and endoscopy and histopathological examination, as well as molecular analysis.

DISCUSSION

Postoperative weight loss is used as a parameter to monitor general recovery. Functional stability can be measured by recording bursting pressure and location. Anastomotic healing can be evaluated macroscopically from the luminal side by endoscopic scoring and from the extraluminal side by assessing adhesion and abscess formation or presence of dehiscence. Histologic examination allows for detailed evaluation of the healing process.

CONCLUSION

The murine model presented in this paper combines adjustable levels of experimental colitis with a standardized method for colorectal anastomosis formation. Extensive options for sample analysis and evaluation of clinical outcomes allow for detailed research of the mechanisms behind defective anastomotic healing.

Innovative approaches for induction of gastrointestinal anastomotic healing: an update on experimental and clinical aspects

PURPOSE

In most cases, traditional techniques to perform an anastomosis following gastrointestinal resections lead to successful healing. However, despite focused research in the field, in certain high-risk situations leakage rates remain almost unchanged. Here, additional techniques may help the surgeon to protect the anastomosis and prevent leakage. We give an overview of some of the latest developments on experimental and clinical techniques for induction of anastomotic healing.

METHODS

We performed a review of the current literature on approaches to improve anastomotic healing.

RESULTS

Many promising approaches with a high clinical potential are in the developmental pipeline. Highly experimental approaches like inhibition of matrix metalloproteinases, stem cell therapy, hyperbaric oxygen therapy, induction of the hypoxic adaptive response, and the administration of growth factors are still in the preclinical phase. Other more clinical developments aim to strengthen the anastomotic suture line mechanically while shielding it from the influence of the microbiome. Among them are gluing, seaming the staple line, attachment of laminar biomaterials, and temporary intraluminal tubes. In addition, individualized bowel preparation, selectively reducing certain detrimental microbial populations could become the next stage of bowel preparation. Compression anastomoses are evolving as an equivalent technique additional to established hand-sewn and stapled anastomoses. Fluorescence angiography and flexible endoscopy could complement intraoperative quality control additionally to the air leak tests. Virtual ileostomy is a concept to prepare the bowel for the easy formation of a stoma in case of leakage.

CONCLUSION

A variety of promising diagnostic and prophylactic measures that may support the surgeon in identifying high-risk anastomoses and support them according to their potential deficits is currently in development.

Protective effect of adipose tissue-derived mesenchymal stromal cells in an experimental model of high-risk colonic anastomosis

BACKGROUND

Dehiscence of intestinal anastomosis results in high morbidity and mortality. The aim of this study was to investigate the effects of locally administered adipose tissue-derived mesenchymal stromal cells in a model of high-risk colonic anastomosis in rats.

METHODS

Seven days after induction of colitis with 2,4,6-trinitrobenzene sulfonic acid, Wistar rats were submitted to a transection of the descending colon followed by end-to-end anastomosis and were then treated with 2×10⁶ adipose tissue-derived mesenchymal stromal cells (from the preperitoneal fat) or an acellular culture solution instilled onto the surface of the anastomosis. At day 14, after macroscopic survey of the abdominal cavity, the anastomotic area was submitted to histologic and immunohistochemical analysis, evaluation of myeloperoxidase activity, fibrosis, epithelial integrity, NF-κ B activation, expression of inflammatory cytokines, and extracellular matrix-related genes.

RESULTS

Anastomotic leakage and mortality associated with high-risk anastomosis decreased with treatment with adipose tissue-derived mesenchymal stromal cells (P < .03). Application of adipose tissue-derived mesenchymal stromal cells resulted in lower histologic scores (P = .011), decreased deposition of collagen fibers (P = .003), preservation of goblet cells (P = .033), decreased myeloperoxidase activity (P = .012), decreased accumulation of CD4+ T-cells (P = .014) and macrophages (P = .011) in the lamina propria, a decrease in the number of apoptotic cells (P = .008), and the activation of NF-κ B (P = .036). Overexpression of IL-17, TNF-α , IFN-γ, and metalloproteinases in the acellular culture solution-treated, high-risk anastomosis group decreased (P < .05) to near normal values with adipose tissue-derived mesenchymal stromal cells treatment.

CONCLUSION

Improvements in outcomes of a high-risk colonic anastomosis with adipose tissue-derived mesenchymal stromal cells therapy reflect the immunomodulatory activity and healing effect of these cells, even after just topical administration and reinforces their use in future translational research.

Feasibility of an Intraluminal Bypass Device in Low Colorectal Anastomosis: Preliminary Results in a Porcine Model

BACKGROUND

The Cologuard CG-100 is a novel intraluminal bypass device designed to reduce the clinical outcomes associated with low colorectal anastomotic leak. The device is inserted transanally, anchored to the colon above the anastomosis, and deployed intraluminally to cover the anastomosis from within. The purpose of this study was to evaluate the safety and performance of the device in a porcine model.

METHOD

Twelve pigs underwent low colorectal anastomosis with insertion of the Cologuard CG-100 device. Contrast material injection, abdominal X-ray, and histologic studies were used to evaluate sealing quality, device positioning, and tissue damage, respectively. The surgeons completed a usability and satisfaction questionnaire after completion of the procedure.

RESULTS

Absolute sealing was observed in all 4 animals euthanized immediately after surgery. In the other 8 animals, the device was kept in situ for 10 days and then extracted. X-ray films with injection of contrast material through a designated injection tube before device removal showed that the sheath and ring were correctly placed. No leak was demonstrated. There were no device-related adverse events, and no critical histological abnormalities were noted in the bowel area that was compressed by the device. The device was found to be easy to insert, position, and extract.

CONCLUSION

The Cologuard CG-100 device efficiently reduced contact between fecal content and low colorectal anastomosis in a porcine model and is easily deployed and extracted. It holds promise for possible clinical use pending further studies.

International consensus statement regarding the use of animal models for research on anastomoses in the lower gastrointestinal tract

PURPOSE

This project aimed to reach consensus on the most appropriate animal models and outcome measures in research on anastomoses in the lower gastrointestinal tract (GIT). The physiology of anastomotic healing remains an important research topic in gastrointestinal surgery. Recent results from experimental studies are limited with regard to comparability and clinical translation.

METHODS

PubMed and EMBASE were searched for experimental studies investigating anastomotic healing in the lower GIT published between January 1, 2000 and December 31, 2014 to assess currently used models. All corresponding authors were invited for a Delphi-based analysis that consisted of two online survey rounds followed by a final online recommendation survey to reach consensus on the discussed topics.

RESULTS

Two hundred seventy-seven original articles were retrieved and 167 articles were included in the systematic review. Mice, rats, rabbits, pigs, and dogs are currently being used as animal models, with a large variety in surgical techniques and outcome measures. Forty-four corresponding authors participated in the Delphi analysis. In the first two rounds, 39/44 and 35/39 participants completed the survey. In the final meeting, 35 experts reached consensus on 76/122 items in six categories. Mouse, rat, and pig are considered appropriate animal models; rabbit and dog should be abandoned in research regarding bowel anastomoses. ARRIVE guidelines should be followed more strictly.

CONCLUSIONS

Consensus was reached on several recommendations for the use of animal models and outcome measurements in research on anastomoses of the lower GIT. Future research should take these suggestions into account to facilitate comparison and clinical translation of results.

An Experimental Study on the Use of Calcium Alginate to Heal Colonic Anastomoses

BACKGROUND

Anastomotic leak is considered the major complication following abdominal surgery. In recent years, the use of a variety of sealing materials for the prevention of leaks has been analyzed. Different biomaterials have been employed as scaffolds to favour tissue repair and regeneration. Among these materials we must mention alginate, a natural polymer with different applications as temporary supporting matrix. The aim of the present study is to evaluate the behavior of both alginate-impregnated sutures and lyophilized alginate sponges in the healing process of colonic anastomes using an experimental animal model.

MATERIAL AND METHODS

A preliminary study was undertaken to select the adequate scaffold. Animals (n = 45) were distributed into three groups: control (colonic anastomosis using non-continuous 5-0 Polyglactin 910 suture), suture (colonic anastomosis using suture impregnated with alginate gel at 4%) and sponge (colonic anastomosis using suture reinforced with lyophilized alginate sponge). The macroscopic and histological variables were assessed at 4, 8 and 12 days after surgical intervention.

RESULTS

No statistically significant differences have been observed between the groups during the analysis of macroscopic variables. Animals with sponge implantation showed a greater degree of epithelial reepithalization, less acute and chronic inflammation and greater collagen deposit.

CONCLUSIONS

The use of lyophilized alginate sponges to reinforce colonic anastomoses in an animal model reduces inflammation and promotes the earlier formation of greater collagen deposits without increasing the number of adhesions or the incidence of stenosis.

Systematic review of experimental studies on intestinal anastomosis

BACKGROUND

The contribution of animal research to a reduction in clinical intestinal anastomotic leakage is unknown, despite numerous experimental studies. In view of the current societal call to replace, reduce and refine animal experiments, this study examined the quality of animal research related to anastomotic healing and leakage.

METHODS

Animal studies on intestinal anastomotic healing were retrieved systematically from PubMed and Embase. Study objective, conclusion and animal model were recorded. Reporting quality and internal validity (reporting of randomization and blinding) were assessed.

RESULTS

A total of 1342 studies were identified, with a rising publication rate. The objectives of most studies were therapeutic interventions (64·8 per cent) and identification of risk factors (27·5 per cent). Of 350 articles studying experimental therapies, 298 (85·1 per cent) reported a positive effect on anastomotic healing. On average, 44·7 per cent of relevant study characteristics were not reported, in particular details on anastomotic complications (31·6 per cent), use of antibiotics (75·7 per cent), sterile surgery (83·4 per cent) and postoperative analgesia (91·4 per cent). The proportion of studies with randomization, blinding of surgery and blinding of primary outcome assessment has increased in the past two decades but remains insufficient, being included in only 62·4, 4·9 and 8·5 per cent of publications respectively. Animal models varied widely in terms of species, method to compromise healing, intestinal segment and outcome measures used.

CONCLUSION

Animal research on anastomotic leakage is of poor quality and still increasing, contrary to societal aims. Reporting and study quality must improve if results are to impact on patients.

Impaired blood supply in the colonic anastomosis in mice compromises healing

Colon anastomotic leakage has a multifactorial etiology and ischemia is considered one of the most important single factors. However, no existing animal models have established a direct link between ischemia and anastomotic leakage. The aim of this study was to establish a model of colon anastomotic leakage as a result of tissue ischemia. In colon anastomoses of 53 C57BL/6 mice, varying degrees of ischemia were induced. Supplying vessels were divided with bipolar coagulation in order to reduce anastomotic breaking strength and create clinical anastomotic leakage. Breaking strength of all the ischemic anastomoses were significantly lower compared with controls. Increasing ischemia resulted in higher rates of large bowel obstruction without creating anastomotic leakage. Healing was compromised as a result of impaired blood supply. However, clinical leakage was absent. Pure ischemia in otherwise healthy experimental animals may be too simple of an approach to create clinical leakage.

Increased collagen maturity with sildenafil citrate: experimental high risk colonic anastomosis model

BACKGROUND

Inadequate healing and high anastomosis leak rates at rectal anastomosis may be due to lack of supportive serosal layer and technical difficulty of low anterior resections. Positive effects of sildenafil on wound healing were observed. The aim of this study was to simulate rectal anastomosis as a technical insufficient anastomosis and investigate the effects of sildenafil on anastomosis healing.

METHODS

Colonic anastomoses were carried out in 64 rats and randomized into four groups, CA-S, complete anastomoses without sildenafil (10 mg/kg for 5 days); CA+S, complete anastomoses with sildenafil; IA-S, incomplete anastomoses without sildenafil; IA+S, incomplete anastomoses with sildenafil. Half of the rats in every group were sacrificed on post-operative day (POD) 3, half of them sacrificed on POD 7. Tissues from the anastomoses were used for functional, histochemical, biochemical investigations.

RESULTS

Sildenafil treatment resulted in increased bursting pressures in IA+S on POD 7 (p=0.010). Collagen maturity was higher in IA+S on POD 3 and POD 7, CA+S on POD 7 (p=0.010; p=0.010; p<0.007). Collagen content was higher in IA+S on POD 7 (p<0.001). Glutathione, hydroxyproline levels were similar. Malondialdehyde levels were lower in IA+S on POD 3 (p<0.001). Epithelization score was higher in IA+S on POD 7 (p=0.007). Inflammation score was higher in CA-S group on POD 3 and POD 7 (p<0.001; p<0.001). Neutrophil score was lower in CA+S on POD 3 (p=0.005).

CONCLUSION

An increase in collagen content, maturity, and epithelization, a decrease in neutrophil infiltration, oxidative stress and better mechanical strength were observed with the administration of sildenafil.

Effects of TachoSil and 5-fluorouracil on colonic anastomotic healing

BACKGROUND

The administration of intraperitoneal (IP) 5-fluorouracil (5-FU) during the early postoperative period after cytoreductive surgery can decrease local cancer recurrence but may also cause impairment of the anastomotic healing. This study examined the effects of the use of this therapy and of the anastomotic sealing with TachoSil, a fibrin-thrombin coated sealant (FTCS), on the healing of colon anastomoses.

MATERIALS AND METHODS

Forty male rats were divided into four groups (1-4, 10 rats each) that underwent transection and anastomosis of the left colon. The anastomoses were covered with FTCS in groups 2 and 4. Saline solution (2 mL/d-groups 1 and 2) or 5-FU (20 mg/kg/d; groups 3 and 4) was administered IP once daily for 3 d. Bursting pressure (BP) was recorded, and the anastomoses were examined macroscopically and graded histologically.

RESULTS

The relative weight loss was significantly higher in group 3 than in the other groups (P = 0.0004). Anastomotic dehiscence, postoperative adhesion formation, perianastomotic collections, and preanastomotic dilatation did not differ significantly among groups. BP was significantly lower in group 3 compared with all other groups (P = 0.001). Neoangiogenesis was significantly lower in group 3 compared with groups 1 and 2 (P = 0.05). Fibroblastic activity was significantly higher in group 1 compared with group 3 (P = 0.035). Inflammatory cell infiltration and collagen deposition did not differ significantly among groups.

CONCLUSIONS

Our results shown that the early postoperative IP chemotherapy with 5-FU impaired the healing of colon anastomoses. However, anastomotic sealing with FTCS reversed some of the negative effects of this therapy.

Critical analysis of cyanoacrylate in intestinal and colorectal anastomosis

BACKGROUND

Although cyanoacrylate glue (CA) has been widely used in various kinds of medical applications, its application in gastrointestinal anastomosis remains limited, and outcomes of experimental studies have not been satisfactory. This systematic review summarizes research regarding CA application in intestinal and colorectal anastomosis, and correlates methodological aspects to experimental outcomes.

METHODS

A systematic literature search was performed using Medline, Embase, Cochrane, and Web-of-Science libraries. Articles were selected if CA was applied to intestinal or colorectal anastomoses. Included articles were categorized according to CA molecular structure; the method details in each study were extracted and analyzed.

RESULTS

Twenty-two articles were included. More than half of the inclusions reported positive outcomes (seven articles) or neutral outcomes (eight articles). Analysis of the methods revealed that methodological details such as CA dosage, time of polymerization were not consistently reported. Porcine studies, inverted anastomosis, and n-butyl-cyanoacrylate studies showed more positive outcomes; everted anastomosis, and oversized sutures might negatively influence the outcomes.

CONCLUSIONS

Owing to the positive outcome from the porcine studies, application of CA in gastrointestinal (GI) anastomosis still seems promising. To achieve a better consistency, more methodological details need to be provided in future studies. Optimizing the dosage of CA, choice of animal model, inverted anastomosis construction, and other method details may improve intestinal and colorectal anastomoses with CA application in future studies.

Prevention of leakage by sealing colon anastomosis: experimental study in a mouse model

BACKGROUND

In colorectal surgery, anastomotic leakage (AL) is the most significant complication. Sealants applied around the colon anastomosis may help prevent AL by giving the anastomosis time to heal by mechanically supporting the anastomosis and preventing bacteria leaking into the peritoneal cavity. The aim of this study is to compare commercially available sealants on their efficacy of preventing leakage in a validated mouse model for AL.

METHODS

Six sealants (Evicel, Omnex, VascuSeal, PleuraSeal, BioGlue, and Colle Chirurgicale Cardial) were applied around an anastomosis constructed with five interrupted sutures in mice, and compared with a control group without sealant. Outcome measures were AL, anastomotic bursting pressure, and death.

RESULTS

In the control group there was a 40% death rate with a 50% rate of AL. None of the sealants were able to diminish the rate of AL. Furthermore, use of the majority of sealants resulted in failure to thrive, increased rates of ileus, and higher mortality rates.

CONCLUSIONS

If sealing of a colorectal anastomosis could achieve a reduction of incidence of clinical AL, this would be a promising tool for prevention of leakage in colorectal surgery. In this study, we found no evidence that sealants reduce leakage rates in a mouse model for AL. However, the negative results of this study make us emphasize the need of systemic research, investigating histologic tissue reaction of the bowel to different sealants, the capacity of sealants to form a watertight barrier, their time of degradation, and finally their results in large animal models for AL.

Healing of ileocolic nitinol compression anastomosis: a novel porcine model of subtotal colectomy

BACKGROUND

There are limited large animal models for the research of novel anastomotic technologies. Subtotal colectomy requires the anastomosis of relatively remote segments of the alimentary tract that are different anatomically, histologically, and pose significant physiological challenge. The quest for a foreign material-free anastomotic line reintroduced nitinol compression anastomosis into clinical use in the last decade.

OBJECTIVE

To evaluate the safety, histological, and physiological parameters of side-to-side ileocolic nitinol compression anastomosis in a newly developed large animal model, mimicking the human subtotal colectomy.

INTERVENTION

Resection of the entire spiral colon with an ileocolic side-to-side compression anastomosis in 12 animals, compared to resection of a short ileal segment in 6 animals. All anastomoses were constructed by using a novel nitinol-based compression device. The animals were followed up to 30 days postoperatively and were reoperated and sacrificed.

RESULTS

All 12 animals underwent successful subtotal colectomy with side-to-side nitinol compression anastomosis. No signs of abdominal infection were found. The increase in the colectomized animals' bodyweight over the postoperative course was significantly lower and the animals presented with longer periods of diarrhea. The histopathology revealed minimal inflammation and foreign body reaction with good alignment of the bowel wall layers in both groups. The anastomotic line width was shown to be reduced during the healing course of the compression anastomoses.

CONCLUSIONS

Side-to-side nitinol compression anastomosis is safe and demonstrates favorable functional and histopathological features. The porcine model of subtotal colectomy can be used for further research of novel anastomotic technologies.

External coating of colonic anastomoses: a systematic review

PURPOSE

Colon anastomotic leakage remains both a frequent and serious complication in gastrointestinal surgery. External coating of colonic anastomoses has been proposed as a means to lower the rate of this complication. The aim of this review was to evaluate existing studies on external coating of colonic anastomoses.

METHODS

CINAHL, EMBASE, and PubMed were searched up to September 2011 to identify studies evaluating external coating of colonic anastomoses.

RESULTS

Forty studies have evaluated 20 different coating materials, of which only fibrin sealant, omental pedicle graft, and hyaluronic acid/carboxymethylcellulose have been used in humans. Fibrin sealant has shown positive, however not significant, results. Omental pedicle graft can be used safely, yet without beneficial effects, whereas hyaluronic acid/carboxymethylcellulose should be avoided due to increased complications. The remaining coating materials have solely been evaluated in experimental animals with many contradictory and few positive results.

CONCLUSIONS

External coating of colonic anastomoses has yet failed to show convincing results. Randomized clinical trials and high-quality experimental studies are warranted to determine the role of fibrin sealant, omental pedicle graft, and other coating materials for prevention of colon anastomotic leakage.