Reduction of oxygenation and blood flow in pedicled bowel segments in the rat and its consequences for anastomotic healing

Quantitative Analysis of Colonic Perfusion Using ICG Fluorescence Angiography and Its Consequences for Anastomotic Healing in a Rat Model

Forty-three rats were randomly assigned to the following four groups: non-ischemic group (Control Group), 1 cm-long ischemic group (Group 1), 2 cm-long ischemic group (Group 2), and 3 cm-long ischemic group (Group 3). The rates of AL were 0% (0/10) in the Control Group, 22.2% (2/9) in Group 1, 25% (2/8) in Group 2, and 50% (4/8) in Group 3. The bursting pressure of the Control Group was significantly higher than that of the other groups (p < 0.01). Regarding the pathological findings, the granulation thickness and the number of blood vessels at the anastomosed site were significantly higher in the Control Group than in Group 3 (p < 0.05). Receiver operating characteristics analysis revealed that Slope was the most significant predictor of AL, with an area under the curve of 0.861. When the cutoff value of Slope was 0.4, the sensitivity and specificity for the prediction of AL were 75% and 81.4%, respectively. Quantitative analysis of ICG fluorescence angiography could predict AL in a rat model.

The Biology of Anastomotic Healing-the Unknown Overwhelms the Known

BACKGROUND

Anastomotic complications are among the most devastating consequences of gastrointestinal surgery. Despite its high morbidity, the factors responsible for anastomotic regeneration following surgical construction remain poorly understood. The aim of this review is to provide an overview of the typical and atypical factors that have been implicated in anastomotic healing.

METHODS

A review and analysis of select literature on anastomotic healing was performed.

RESULTS

The healing of an anastomotic wound mirrors the phases of cutaneous wound healing- inflammation, proliferation, and remodeling. The evidence supporting much of the traditional dogma for optimal anastomotic healing (ischemia, tension, nutrition) is sparse. More recent research has implicated atypical factors that influence anastomotic healing, including the microbiome, the mesentery, and geometry. As technology evolves, endoscopic approaches may improve anastomotic healing and in some cases may eliminate the anastomosis altogether.

DISCUSSION

Much remains unknown regarding the mechanisms of anastomotic healing, and research should focus on elucidating the dynamics of healing at a molecular level. Doing so may help facilitate the transition from traditional surgical dogma to evidence-based medicine in the operating room.

Risk factors and endoscopic treatment for anastomotic stricture after resection in patients with colorectal cancer

INTRODUCTION

Benign strictures are frequent complications following colorectal surgery, with an incidence of up to 20%. Endoscopic treatment is safe and effective but there is not enough evidence for establishing stricture management at that anatomic level.

AIM

To determine the risk factors associated with the development of stricture in patients with colorectal cancer and describe endoscopic treatment in those patients.

MATERIALS AND METHODS

A retrospective study was conducted on patients with colorectal cancer that underwent surgery and anastomosis, evaluated through colonoscopy, within the time frame of 2014 to 2019.

RESULTS

Of the 213 patients included in the study, 18.3% presented with stricture that was associated with the type of surgery. Intersphincteric resection was a risk factor (OR = 18.81, 95% CI: 3.31-189.40, p < .001). A total of 69.2% patients with stricture had a stoma, identifying it as a risk factor for stricture (OR = 7.07, 95% CI: 3.10-16.57, p < .001). Mechanical anastomotic stapling was performed in 87.4% of the patients that did not present with stricture, identifying it as a protective factor (OR = 0.41, 95% CI: 0.16-1.1, p = .04). Endoscopic treatment was required in 69.2% of the patients and provided favorable results in 83.3%. Only 2.6% of the patients had recurrence. No complications were reported.

CONCLUSION

Intersphincteric resection and the presence of a stoma were independent risk factors for stricture, and mechanical anastomosis was a protective factor against stricture development. Endoscopic treatment was safe and effective.

Systematic Review on the Influence of Tissue Oxygenation on Gut Microbiota and Anastomotic Healing

BACKGROUND

Anastomotic leak rates have not improved over several decades despite improvements in surgical techniques and patient care. The gut microbiome has been implicated in the development of leaks. The exact mechanisms by which tissue oxygenation affects gut microbial composition and anastomotic healing physiology are unclear. Also, commonly used carbon dioxide (CO₂) is a known vasodilator that improves tissue oxygen tension. We performed a systematic review to determine the influence of hyperoxia, hypoxia, and hypercapnia on the gut microbiome and anastomotic healing.

METHODS

A literature search was performed in MEDLINE, EMBASE, and COCHRANE to identify studies investigating the effects of hyperoxia, hypoxia, and hypercapnia on anastomotic healing and gut microbiota published between 1998 and 2018. Two reviewers screened the articles for eligibility and quality. Fifty-three articles underwent full text review, and a narrative synthesis was undertaken.

RESULTS

Hyperoxia is associated with better anastomotic healing, increased gastrointestinal oxygen tension, and may reduce gut anaerobes. Hypoxia is associated with poor healing and increased gut anaerobes. However, it is unclear if hypoxia is the most important predictor of anastomotic leaks. Low pressure CO₂ pneumoperitoneum and mild systemic hypercapnia are both associated with increased gastrointestinal oxygen tension and may improve anastomotic healing. We found no studies which investigated the effect of hypercapnia on gut microbiota in the context of anastomotic healing.

CONCLUSIONS

Tissue oxygenation influences gut anastomotic healing, but little evidence exists to demonstrate the influence on the gut microbiome in the context of healing. Further studies are needed to determine if anastomotic microbiome changes with altered tissue oxygenation and if this affects healing and leak rates. If confirmed, altering tissue oxygenation through hyperoxia or hypercapnia could be feasible means of altering the microbiome such that anastomotic leak rates reduce.

Enhanced anastomotic healing by Daikenchuto (TJ-100) in rats

Daikenchuto (DKT), a traditional Japanese medicine, is widely used to treat various gastrointestinal disorders. This study aimed to investigate whether DKT could promote the anastomotic healing in a rat model. Pedicled colonic segments were made in left colon by ligation of the feeding arteries, and then intestinal continuity was restored. Colonic blood flow was analyzed by using ICG fluorescence imaging: Fmax, Tmax, T1/2, and Slope were calculated. Anastomotic leakage (AL) was found in 6 of 19 rats (31.6%) in the control group, whereas in 1 of 16 rats (6.2%) in the DKT group. The Fmax and Slope of DKT group were significantly higher than those of control group. DKT could promote the anastomotic healing, with the higher bursting pressure on postoperative day (POD) 2 and 5, the larger granulation thickness on POD 5, and neoangiogenesis on POD 5. Histological examination showed DKT exhibited a decreased inflammatory cell infiltration, enhanced fibroblast infiltration, and enhanced collagen density on POD 5. In the DKT group, the levels of TGFβ1 on POD 2 and VEGFα on POD5 were significantly higher, whereas the level of TNFα on POD 2 was significantly lower. Therefore, DKT could be effective for the prevention of AL following colorectal surgery.

Effect of intraoperative PEEP application on colonic anastomoses healing: An experimental animal study

PURPOSE

This study aimed to assess the effect of intraoperative PEEP intervention on the healing of colonic anastomoses in rabbits.

MATERIALS AND METHODS

Thirty-two New Zealand type male rabbits were divided into two groups of sixteen animals each. Following ventilation with tracheostomy, colonic resection and anastomosis were performed in both groups. While 10 cm H2O PEEP level was applied in Group I (PEEP), Group II (ZEEP) was ventilated without PEEP throughout the surgery. Half of the both PEEP and ZEEP group animals were killed on the third postoperative day, while the remaining half on the seventh. Anastomotic bursting pressures, the tissue concentrations in hydroxyproline, and histological assessments were performed. Besides, intraoperative oxygen saturation and postoperative arterial blood gas parameters were also compared.

RESULTS

On the first postoperative day, both arterial oxygen tension (PO2) and oxygen saturation (SO2) in the PEEP group were significantly higher than in the ZEEP group. On the seventh postoperative day, the bursting pressures of the anastomoses were significantly higher in the PEEP group, however the hydroxyproline content was significantly lower in the PEEP group than that in the ZEEP group. At day 7, PEEP group was significantly associated with increased neoangiogenesis compared with the ZEEP group.

CONCLUSION

The anastomotic healing process is positively influenced by the intraoperative PEEP application.

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.

The effect of carbon dioxide pneumoperitoneum on the healing colonic anastomosis in rats

PURPOSE

To investigate the effects of pneumoperitoneum on colonic anastomosis healing.

METHODS

Colonic anastomosis was performed in 120 rats divided into four groups: Group I - pneumoperitoneum before laparotomy, Group II - pneumoperitoneum after laparorrhaphy, Group III - pneumoperitoneum before laparotomy and after laparorrhaphy, Group IV - no pneumoperitoneum (control group). Pneumoperitoneum pressure was 5 mmHg. Animals were killed on the 3rd, 7th and 14th postoperative day. Histopathological features, anastomosis breaking strength, collagen histomorphometry and hydroxyproline concentration were assessed.

RESULTS

Breaking strength between groups: (day 3, p=0.165; day 7, p=0.219; day 14, p=0.539). Histopathology revealed that group II had, on day 7, less infiltration of mononuclear cells (p=0.006), greater infiltration of polymorphonuclear cells (p=0.001) and greater necrosis (p=0.001); and on day 14, less fibrosis. Histomorphometry revealed a decrease in collagen in groups I and III (p<0.001) on day 7 and an increase in groups I and II on day 14 (p<0.001). Hydroxyproline concentration was similar for groups on days 3 (p=0.152), 7 (p=0.913) or 14 (p=0.981).

CONCLUSION

Carbon dioxide does not impair the healing of colonic anastomosis in rats.

Local ischaemia does not influence anastomotic healing: an experimental study

The role of local ischaemia in the pathogenesis of colorectal anastomotic leakage (AL) is not known. This study investigates the role of local ischaemia caused by sutures in an experimental colonic anastomosis model. 36 mice were assigned to three types of anastomosis, all using running sutures; in the first group 5 stitches were used, in the second group 12 stitches were used, and in the third group at least 30 stitches were used. After 7 days the mice were re-operated, signs of AL were scored, and coronal sections of the anastomosis were histologically analyzed. The distribution of weight was not significantly different between the three groups. Mortality was 44% and not significantly different between the groups (group 1: 5/12, group 2: 4/12, and group 3: 7/12, p = 0.72). Faecal and purulent AL were observed in 6 animals in group 1, 2 in group 2, and 3 in group 3 (group 1: 50%, group 2: 17%, and group 3: 25%, p = 0.19). The distance between the two colonic edges (group 1: 0.51 μm, group 2: 1.34 μm, and group 3: 0.53 μm, p = 0.18), the diameter of the lumen at the site of the anastomosis (group 1: 2.92 μm, group 2: 4.06 μm, and group 3: 3.2 μm, p = 0.9), and the largest diameter of the lumen proximally to the anastomosis (group 1: 2.05 μm, group 2: 3.1 μm, and group 3: 2.6 μm, p = 0.25) were not different between the groups. Histological parameters of wound healing were not significantly different for the three groups. In this study no macroscopic and microscopic differences were observed between colon anastomosis with 5 stitches versus 12 and >30 stitches. This might indicate that local ischaemia does not negatively influence colonic wound healing.

How to assess intestinal viability during surgery: A review of techniques

Objective and quantitative intraoperative methods of bowel viability assessment are essential in gastrointestinal surgery. Exact determination of the borderline of the viable bowel with the help of an objective test could result in a decrease of postoperative ischemic complications. An accurate, reproducible and cost effective method is desirable in every operating theater dealing with abdominal operations. Numerous techniques assessing various parameters of intestinal viability are described by the studies. However, there is no consensus about their clinical use. To evaluate the available methods, a systematic search of the English literature was performed. Virtues and drawbacks of the techniques and possibilities of clinical application are reviewed. Valuable parameters related to postoperative intestinal anastomotic or stoma complications are analyzed. Important issues in the measurement and interpretation of bowel viability are discussed. To date, only a few methods are applicable in surgical practice. Further studies are needed to determine the limiting values of intestinal tissue oxygenation and flow indicative of ischemic complications and to standardize the methods.

Comparative study of balloon and metal olive dilators for endoscopic management of benign anastomotic rectal strictures: clinical and cost-effectiveness outcomes

BACKGROUND

Postoperative anastomotic strictures frequently complicate colorectal resection. Currently, various endoscopic techniques are being employed in their management, but the establishment of an optimal therapeutic strategy is still pending. The purpose of our study is to compare through-the-scope (TTS) balloon dilators versus Eder-Puestow metal olive dilators in the treatment of postoperative benign rectal strictures, considering the clinical outcome and cost-effectiveness of each method.

METHODS

A total of 39 patients with benign anastomotic rectal stenosis were retrospectively studied. In group A, 15 patients underwent dilation with Eder-Puestow metal olives, while in group B 19 patients were treated by means of TTS balloon dilators. The technical and clinical success of dilation, complications, number of repeated sessions required, disease-free time intervals, and the overall cost of each procedure were evaluated.

RESULTS

Dilations were technically successful in all patients. No major complications occurred in either group. The number of dilations needed, rate of stricture recurrence, and duration of stenosis-free time intervals were not statistically significantly different between the two groups. Both methods proved more effective in older patients, given the greater number of dilations required in younger patients of both groups and higher frequency of stricture relapse in younger balloon-dilated patients (median 64.00 years) compared with older ones (median 75.00 years) (p = 0.001). An indisputable advantage of the Eder-Puestow technique, compared with TTS balloon dilators, is the low cost of equipment (median 22.30 compared with 680 , respectively; p < 0.001).

CONCLUSION

Endoscopic dilation of postoperative benign rectal strictures is equally effective and safe, especially in older patients, when performed by Eder-Puestow bougies or TTS balloon dilators. However, metal olivary tips seem to surpass balloon dilators when considering the obvious economical benefits of the first method.