Selective cyclo-oxygenase 2 inhibition affects ileal but not colonic anastomotic healing in the early postoperative period

Evaluation of cats treated with robenacoxib after gastrointestinal surgery

OBJECTIVES

The aim of the study was to determine if cats administered robenacoxib immediately after gastrointestinal surgery have a similar complication rate to cats that were not administered robenacoxib.

METHODS

Medical records were reviewed for 154 cats that underwent gastrointestinal surgery between December 2015 and September 2021 in this retrospective study. Data collected included patient signalment, presenting complaint, surgical procedure(s) performed, robenacoxib administration and major postoperative complications. Cats were excluded if they did not have a 2-week postoperative follow-up examination. Two groups were analyzed: group R (postoperative robenacoxib administration) consisted of 43 cats; and group C (no postoperative robenacoxib administration) consisted of 111 cats.

RESULTS

Complications occurred in 10/43 (23.2%) cats in group R and 34/111 (30.6%) cats in group C. Major complications occurred in 1/43 (2.3%) in group R and 14/111 (12.6%) in group C. Minor complications occurred in 9/43 (20.9%) cats in group R and 20/111 (18.0%) cats in group C. One of 43 cats (2.3%) in group R and 10/111 (9.0%) cats in group C were euthanized or died within 0-16 days after gastrointestinal surgery.

CONCLUSIONS AND RELEVANCE

Cats that were administered robenacoxib postoperatively did not have an increase in major postoperative complications after gastrointestinal surgery compared with cats that were administered an alternative analgesic medication. The use of robenacoxib in cats after gastrointestinal surgery may be a safe analgesic option for postoperative pain control.

The Combined Effect of Western Diet Consumption and Diclofenac Administration Alters the Gut Microbiota and Promotes Anastomotic Leakage in the Distal Colon

BACKGROUND

Obesity, Western diet (WD) consumption, and the use of non-steroidal anti-inflammatory drugs (NSAIDs) are co-occurring and modifiable factors associated with microbiome dysbiosis and anastomotic leakage. We studied the combined effect of a Western-type diet (WD) and diclofenac, a standard NSAID used in surgical patients, on anastomotic healing and gut microbiota composition following distal colon resection.

METHODS

Forty-two rats were fed a WD for 6 weeks, after which they were randomized to either parenteral diclofenac 3 mg/kg/day or saline started on the day of surgery and continued for three days. The surgical procedure involved distal colon resection with anastomosis. Animals were sacrificed on postoperative day (POD)-3 or POD-5. Anastomotic healing was assessed and correlated with diclofenac treatment and gut microbiota composition, analyzed by 16S rRNA marker gene amplicon sequencing. Mucosal integrity of the anastomosis was evaluated by histological analysis.

RESULTS

Anastomotic leakage rate was 100 percent (8/8) in diclofenac-treated rats and 10 percent (1/10) in saline-treated controls on POD-5. Diclofenac administration in WD-fed animals induced a shift in microbiota composition, characterized by an increase in microbiota diversity on POD-5 and a significant 15-fold, 4-fold, and 16-fold increase of Proteobacteria, Bacteroidetes, and Verrucomicrobia, respectively. Diclofenac use in WD-fed animals caused mucosal erosion on POD-5, a phenomenon not observed in control animals.

CONCLUSIONS

Consumption of a Western diet combined with diclofenac administration shifts the microbiota composition, associated with clinically relevant AL in the distal colon of rats.

Perioperative cyclooxygenase inhibition and postoperative pancreatic fistula after pancreatoduodenectomy: A systematic review and meta-analysis of comparative studies

BACKGROUND

Nonsteroidal anti-inflammatory drug (NSAID) use has been investigated as a modifiable risk factor for postoperative pancreatic fistula (POPF) after pancreatoduodenectomy (PD). This study comprises a systematic review and meta-analysis examining the impact of perioperative NSAID use on rates of POPF after PD.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020-compliant systematic review was performed. Pooled mean differences (MD), odds ratios (OR), and risk ratios with 95% CIs were calculated.

RESULTS

Seven studies published from 2015 to 2021 were included, reporting 2851 PDs (1372 receiving NSAIDs and 1479 not receiving NSAIDs). There were no differences regarding blood loss (MD -99.40 mL; 95% CI, -201.71 to 2.91; P = .06), overall morbidity (OR 1.05; 95% CI, 0.68-1.61; P = .83), hemorrhage (OR 2.35; 95% CI, 0.48-11.59; P = .29), delayed gastric emptying (OR 0.98; 95% CI, 0.60-1.60; P = .93), bile leak (OR 0.68; 95% CI, 0.12-3.89; P = .66), surgical site infection (OR 1.02; 95% CI, 0.33-3.22; P = .97), abscess (OR 0.99; 95% CI, 0.51-1.91; P = .97), clinically relevant POPF (OR 1.18; 95% CI, 0.84-1.64; P = .33), readmission (OR 0.94; 95% CI, 0.61-1.46; P = .78), or reoperation (OR 0.82; 95% CI, 0.33-2.06; P = .68). NSAID use was associated with a shorter hospital stay (MD -1.05 days; 95% CI, -1.39 to 0.71; P < .00001).

CONCLUSION

The use of NSAIDs in the perioperative period for patients undergoing PD was not associated with increased rates of POPF.

COX-2 inhibitor delivery system aiming intestinal inflammatory disorders

Selective COX-2 inhibitors such as etoricoxib (ETX) are potentially indicated for the treatment of intestinal inflammatory disorders. However, their systemic administration provokes some off-site secondary effects, decreasing the desirable local effectiveness. To circumvent such limitations, herein an ETX delivery system based on electrospun fibrous meshes (eFMs) was proposed. ETX at different concentrations (1, 2, and 3 mg mL-1) was loaded into eFMs, which not affect the morphology and the mechanical properties of this drug delivery system (DDS). The ETX showed a burst release within the first 12 h, followed by a faster release until 36 h, gradually decreasing over time. Importantly, the ETX studied concentrations were not toxic to human colonic cells (i.e. epithelial and fibroblast). Moreover, the DDS loading the highest concentration of ETX, when tested with stimulated human macrophages, promoted a reduction of PGE2, IL-8 and TNF-α secretion. Therefore, the proposed DDS may constitute a safe and efficient treatment of colorectal diseases promoted by inflammatory disorders associated with COX-2.

Immune Modulatory Effects of Nonsteroidal Anti-inflammatory Drugs in the Perioperative Period and Their Consequence on Postoperative Outcome

Nonsteroidal anti-inflammatory drugs are among the most commonly administered drugs in the perioperative period due to their prominent role in pain management. However, they potentially have perioperative consequences due to immune-modulating effects through the inhibition of prostanoid synthesis, thereby affecting the levels of various cytokines. These effects may have a direct impact on the postoperative outcome of patients since the immune system aims to restore homeostasis and plays an indispensable role in regeneration and repair. By affecting the immune response, consequences can be expected on various organ systems. This narrative review aims to highlight these potential immune system-related consequences, which include systemic inflammatory response syndrome, acute respiratory distress syndrome, immediate and persistent postoperative pain, effects on oncological and neurologic outcome, and wound, anastomotic, and bone healing.

Anastomotic healing in a rat model of peritonitis after non-steroidal anti-inflammatory drug administration

The tissue inflammatory response can influence the outcome of anastomotic healing. Anastomotic leakage represents a dreadful complication after gastrointestinal surgery, in particular sepsis and intra-abdominal infections impair the restorative process of colic anastomoses. It has been debated whether the administration of nonsteroidal anti-inflammatory drugs (NSAIDs) is a risk factor for dehiscence, since many patients receive NSAIDs in the early postoperative period. Our aim was, for the first time, to analyze the morpho-functional effects of postoperative administration of two commonly used NSAIDs, Diclofenac and Ketorolac, on the healing process of colo-colic anastomoses constructed under condition of fecal peritonitis in a rat model. Sixty adult male rats underwent two surgical procedures: peritonitis induction and colo-colic anastomosis, and were divided into three groups: 20 rats received saline; 20 rats 4 mg/kg Diclofenac and 20 rats 5 mg/kg Ketorolac. We assessed anastomosis strength, morphological features of tissue wound healing, immunohistochemical metalloproteinase 9 (MMP9) expression and collagen deposition and content by Sirius red staining and hydroxyproline level. We found no significant difference in bursting pressure, collagen content and organization and morphological features between the groups, except a significantly reduced presence of inflammatory cells and MMP9 expression in the groups treated with NSAIDs. Our findings showed that Diclofenac and Ketorolac administration did not affect post-surgical healing and did not increase the leakage risk of colo-colic anastomoses during peritonitis.

Parecoxib's effects on anastomotic and abdominal wound healing: a randomized Controlled trial

BACKGROUND

Current evidence regarding the effects of selective cyclooxygenase inhibitors on gastrointestinal anastomoses is controversial. An experimental randomized control study was conducted in our institution to histopathologically evaluate the consequences of parecoxib, on intestinal and abdominal wound healing.

METHODS

Twenty-four adult Wistar rats underwent laparotomy, ascending colon transection, and hand-sewn anastomosis. They were randomized to receive either parecoxib (0.5 mg/kg twice daily) or 0.9% normal saline by intraperitoneal injection postoperatively. Animals were euthanatized either on the third or the seventh postoperative day. Semiquantitative methods were used to evaluate both intestinal and abdominal wounds for inflammatory cell composition, angiogenesis, fibroblasts, granular tissue, collagen deposition, epithelization, and presence of necrosis, exudate, and abscess formation. Results are presented as (parecoxib: median [IQR] versus control: median [IQR], P-value).

RESULTS

No macroscopic anastomotic leakage or wound dehiscence was observed. Intestinal anastomoses in the parecoxib group, showed significantly decreased epithelization (2 [1] versus 3 [1], [P = 0.004]) and collagen deposition (2 [0] versus 3 [1], [P = 0.041]). No difference was observed in angiogenesis (3 [1] versus 2.5 [1], [P = 0.158]). Abdominal wall specimens appeared to demonstrate decreased epithelization (2 [2] versus 4 [0.5], [P = 0.0004]) in the treatment group. No difference between the two groups was identified regarding collagen deposition (2.5 [1] versus 2 [0.5], [P = 0.280]) and angiogenesis (2.5 [1] versus 2 [1], [P = 0.633]). Necrosis was significantly more present in the parecoxib group in both specimen types, (3.5 [1] versus 2.5 [1], [P = 0.017]) and (3 [1] versus 1 [0.5], [P < 0.0001]).

CONCLUSIONS

The present study shows that despite the absence of clinical adverse effects, parecoxib can impair anastomotic and abdominal wound healing on a histopathological level.

Functional mucous layer and healing of proximal colonic anastomoses in an experimental model

BACKGROUND

Anastomotic leakage (AL) is the most dreaded complication after colorectal surgery, causing high morbidity and mortality. Mucus is a first line of defence against external factors in the gastrointestinal tract. In this study, the structural mucus protein Muc2 was depleted in genetically engineered mice and the effect on healing of colonic anastomoses studied in an experimental model.

METHODS

Mice of different Muc2 genotypes were used in a proximal colonic AL model. Tissues were scored histologically for inflammation, bacterial translocation was determined by quantitative PCR of bacterial 16S ribosomal DNA, and epithelial cell damage was determined by assessing serum levels of intestinal fatty acid-binding protein.

RESULTS

Of 22 Muc2-deficient (Muc2^-/- ) mice, 20 developed AL, compared with seven of 22 control animals (P < 0·001). Control mice showed normal healing, whereas Muc2^-/- mice had more inflammation with less collagen deposition and neoangiogenesis. A tendency towards higher bacterial translocation was seen in mesenteric lymph nodes and spleen in Muc2^-/- mice. Intestinal fatty acid-binding protein levels were significantly higher in Muc2^-/- mice compared with controls (P = 0·011).

CONCLUSION

A functional mucous layer facilitates the healing of colonic anastomoses. Clinical relevance Colorectal anastomotic leakage remains the most dreaded complication after colorectal surgery. It is known that the aetiology of anastomotic leakage is multifactorial, and a role is suggested for the interaction between intraluminal content and mucosa. In this murine model of proximal colonic anastomotic leakage, the authors investigated the mucous layer at the intestinal mucosa, as the first line of defence, and found that a normal, functioning mucous layer is essential in the healing process of colonic anastomoses. Further research on anastomotic healing should focus on positively influencing the mucous layer to promote better postoperative recovery.

Effects of Lornoxicam on Anastomotic Healing: A Randomized, Blinded, Placebo-Control Experimental Study

Introduction and Aim. With the implementation of multimodal analgesia regimens, Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) are often administered for optimal pain control and reduction of opioid use. The aim of the study was to examine the effects of lornoxicam, a NSAID, on anastomotic healing employing an animal model. Materials and Methods. A total of 28 Wistar rats were randomly assigned in two groups. All animals underwent ascending colonic transection followed by an end-to-end hand sewn anastomosis. Group 1 received intraperitoneally lornoxicam before and daily after surgery. Group 2 received intraperitoneally an equal volume of placebo. Half of the animals in each group were euthanized on the 3rd pod and the remaining on the 7th pod. Macro- and microscopic indicators of anastomotic healing were compared using a two-tailed Fisher exact test. Results. The lornoxicam group significantly decreased fibroblast in growth and reepithelization of the mucosa at the anastomotic site on the 3rd pod and significantly increased occurrence of deep reaching defects, necrosis, and microabscess on the 7th pod. Conclusion. Lornoxicam administration during the perioperative period adversely affects histologic parameters of intestinal anastomotic healing. These effects of lornoxicam administration were not found to induce significant increase of anastomotic dehiscence in the rat model.

Colorectal anastomotic healing: why the biological processes that lead to anastomotic leakage should be revealed prior to conducting intervention studies

BACKGROUND

Anastomotic leakage (AL) remains the most dreaded complication after colorectal surgery and causes high morbidity and mortality. The pathophysiology of AL remains unclear, despite numerous studies that have been conducted on animals and humans, probably due to the undetermined healing process of colorectal anastomoses. Increasing basic knowledge on this healing process may shed more light on causal factors of AL, and additionally reduce the quantity and accelerate the quality of experimental studies. In this debate article, our aim was to provide different perspectives on what is known about the colorectal healing process in relation to wound healing and AL.

DISCUSSION

Since knowledge on anastomotic healing is lacking, it remains difficult to conclude which factors are essential in preventing AL. This is essential information in the framework of humane animal research, where the focus should lie on Replacement, Reduction and Refinement (3Rs). While many researchers compare anastomotic healing with wound healing in the skin, there are substantial recognized differences, e.g. other collagen subtypes and different components involved. Based on our findings in literature as well as discussions with experts, we advocate stop considering anastomotic healing in the gastrointestinal tract and cutaneous healing as a similar process. Furthermore, intervention studies should at least address the anastomotic healing process in terms of histology and certain surrogate markers. Finally, the anastomotic healing process ought to be further elucidated - with modern techniques to achieve 3Rs in animal research--to provide starting points for potential interventions that can prevent AL.

Effect of Postoperative Diclofenac on Anastomotic Strength and Histologic Healing in Rabbit Small Intestine

In this experimental study, we investigated the effects of a 5-day postoperative treatment with the nonsteroidal anti-inflammatory drug (NSAID) diclofenac on anastomotic healing in rabbits. NSAIDs are widely used analgesics in today's “fast-track surgery,” raising concerns about their potential negative effects on healing in humans. A total of 33 New Zealand White female rabbits underwent laparotomy and 2 separate end-to-end anastomoses of the ileum.. The animals were randomized to receive subcutaneous diclofenac 4 mg/kg/d (17 experimental rabbits) or subcutaneous isotonic saline 0.1 mL/kg/d (16 control rabbits) postoperatively. On the fifth postoperative day, the animals were humanely killed, and anastomotic leakage, anastomotic breaking strength, and histopathologic changes were evaluated. Breaking strength in the diclofenac group was 21% lower than in the placebo group (P = 0.027). Anastomotic leakage was found in 4 rabbits in the diclofenac group (26.7%). The rabbits treated with diclofenac demonstrated a 16% lower collagen deposition compared with the placebo group (P = 0.008). In our study, postoperative treatment with diclofenac had a negative effect on the anastomotic healing and strength in the ileum of rabbits. Caution should be taken in the use of diclofenac after gastrointestinal surgery.

Postoperative nonsteroidal anti-inflammatory drugs and risk of anastomotic leak: meta-analysis of clinical and experimental studies

BACKGROUND

Enhanced recovery programs following colorectal resection recommend the use of nonsteroidal anti-inflammatory drugs (NSAIDs) as part of multimodal analgesia. The present study aimed to assess whether postoperative NSAID use increased the risk of anastomotic leak.

METHODS

A systematic review of published literature was performed for studies comparing anastomotic leak following NSAID administration versus control. Meta-analysis was conducted for studies in human patients and experimental animal models. The primary endpoint was anastomotic leak.

RESULTS

The final analysis included 8 studies in humans and 12 experimental animal studies. Use of NSAIDs was significantly associated with anastomotic leak in humans (8 studies, 4,464 patients, odds ratio [OR] 2.14; p < 0.001). This effect was seen with nonselective NSAIDs (6 studies, 3,074 patients, OR 2.37; p < 0.001), but not with selective NSAIDs (4 studies, 1,223 patients, OR 2.32; p = 0.170). There was strong evidence of selection bias from all clinical studies, with additional inconsistent definitions and outcomes assessment. From experimental animal models, anastomotic leak was more likely with NSAID use (ten studies, 575 animals, OR 9.51; p < 0.001). Bursting pressures at day 7 were significantly lower in NSAID versus controls (7 studies, 168 animals, weighted mean difference -35.7 mmHg; p < 0.001).

CONCLUSIONS

Emerging data strongly suggest that postoperative NSAIDs are linked to anastomotic leak, although most studies are flawed and may be describing pre-existing selection bias. However, when combined with experimental data, these increasing concerns suggest caution is needed when prescribing NSAIDs to patients with pre-existing risk factors for leak, until more definitive evidence emerges.

Diclofenac causes anastomotic leakage in the proximal colon but not in the distal colon of the rat

BACKGROUND

Nonsteroidal anti-inflammatory drugs have been associated with anastomotic leakage. It was studied if diclofenac affects anastomoses differently depending on the location in the gut.

METHODS

Ninety-five rats were randomized to 6 groups with an anastomosis in either ileum (IL), proximal colon (PC), or distal colon (DC). Groups IL+ (n = 10), PC+ (n = 30), and DC+ (n = 10) received diclofenac (3 mg/kg/day) from day 0 until sacrifice on day 3. Group PC- (n = 15) did not receive diclofenac. Groups PC1+ and PC2+ (n = 15 each) were given diclofenac from day 1 to 4 and from day 2 to 5.

RESULTS

Leak rates were 10/10 in group IL+, 22/30 in PC+, 1/10 in DC+, and 1/15 in PC-. Delayed administration of diclofenac by 1 or 2 days (6/15, P = .05) resulted in reduced leakage rates. Mechanical strength results corresponded with leak rates.

CONCLUSIONS

Diclofenac causes leakage of anastomoses in rat IL and PC, but not in the DC. This suggests a role for the ileal and proximal colonic content in diclofenac-induced leakage.

Proceedings of the first international summit on intestinal anastomotic leak, Chicago, Illinois, October 4-5, 2012

OBJECTIVE

The first international summit on anastomotic leak was held in Chicago in October, 2012 to assess current knowledge in the field and develop novel lines of inquiry. The following report is a summary of the proceedings with commentaries and future prospects for clinical trials and laboratory investigations.

BACKGROUND

Anastomotic leakage remains a devastating problem for the patient, and a continuing challenge to the surgeon operating on high-risk areas of the gastrointestinal tract such as the esophagus and rectum. Despite the traditional wisdom that anastomotic leak is because of technique, evidence to support this is weak-to-non-existent. Outcome data continue to demonstrate that expert high-volume surgeons working in high-volume centers continue to experience anastomotic leaks and that surgeons cannot predict reliably which patients will leak.

METHODS

A one and one-half day summit was held and a small working group assembled to review current practices, opinions, scientific evidence, and potential paths forward to understand and decrease the incidence of anastomotic leak.

RESULTS

RESULTS of a survey of the opinions of the group demonstrated that the majority of participants believe that anastomotic leak is a complicated biologic problem whose pathogenesis remains ill-defined. The group opined that anastomotic leak is underreported clinically, it is not because of technique except when there is gross inattention to it, and that results from animal models are mostly irrelevant to the human condition.

CONCLUSIONS

A fresh and unbiased examination of the causes and strategies for prevention of anastomotic leak needs to be addressed by a continuous working group of surgeons, basic scientists, and clinical trialists to realize a real and significant reduction in its incidence and morbidity. Such a path forward is discussed.

The effect of celecoxib administration on the healing and neovascularization of colonic anastomosis in rats

BACKGROUND

The aim of this experimental study was to investigate whether the perioperative administration of the selective cyclooxygenase-2 inhibitor celecoxib affects the angiogenetic process and the healing of colonic anastomoses.

METHODS

Seventy-two male Wistar rats underwent colonic resection and anastomosis. Celecoxib (10 mg/kg/day-celecoxib group) or placebo (control group) was administered perioperatively. Rats of both groups were sacrificed on either the third or the seventh postoperative day and bursting pressures of the anastomoses were measured. Gelatine-degrading matrix metalloproteinases (MMPs) were identified with gelatine zymography, and proMMP-2 and vascular endothelial growth factor (VEGF) levels from both anastomotic site and tissue adjacent to the anastomosis were evaluated. Histologic evaluation of microvessels was performed by immunohistochemistry using an anti-CD34 monoclonal antibody.

RESULTS

Celecoxib did not significantly decrease anastomotic bursting pressures. Gelatin zymography revealed the presence of MMP-2, proMMP-2, and proMMP-9. MMP concentration was higher at the anastomotic tissue as compared with tissue distant to the anastomosis. Celecoxib resulted in a significant reduction in proMMP-2 levels at the anastomosis at both third and seventh postoperative day. VEGF levels from the anastomotic tissue were also found lower in the celecoxib group. Histological examination showed a celecoxib-induced reduction of newly formed CD34-stained vessels.

CONCLUSIONS

Although the perioperative administration of celecoxib resulted in suppression of angiogenesis in the newly formed anastomoses, bursting pressures remained unaffected and subsequently safety was not compromised.

Diclofenac causes more leakage than naproxen in anastomoses in the small intestine of the rat

BACKGROUND

Non-steroid anti-inflammatory drugs such as the cyclooxygenase isoenzyme inhibitors diclofenac and naproxen are increasingly used for perioperative pain relief, while their potential effects on wound healing are scarcely investigated.

METHODS

In 104 male Wistar rats, an anastomosis was constructed in both colon and ileum. The rats were divided into groups who received diclofenac (4 mg kg(-1) day(-1)) or naproxen (10 mg kg(-1) day(-1)) daily from the day of surgery or from day 3 after surgery. Animals were killed on day 3 or 7 and analysed for signs of anastomotic dehiscence and wound strength of anastomoses and abdominal fascia.

RESULTS

Anastomotic leakage in the ileum (p < 0.0001) and mortality rates (p = 0.001) were significantly increased in the diclofenac group. On day 7, the anastomotic bursting pressure in the ileum remained below that of the controls in the diclofenac- and naproxen-treated rats. When administration of diclofenac was postponed to day 3 after surgery, anastomotic dehiscence was almost absent. The colonic anastomosis and abdominal wall always remained unaffected.

CONCLUSIONS

This study implies that immediate postoperative administration of diclofenac and, to a far lesser extent, naproxen can affect healing in the ileal anastomosis in the rat. This negative effect can be prevented by a short postoperative delay in administration. On steroid anti-inflammatory drugs such as the cyclooxygenase isoenzyme inhibitors diclofenac and naproxen are increasingly used for perioperative pain relief, while their potential effects on wound healing are scarcely investigated.

Increased risk for complications after colorectal surgery with selective cyclo-oxygenase 2 inhibitor etoricoxib

BACKGROUND

Cyclo-oxygenase 2 inhibitors can be used for pain treatment after colorectal surgery.

OBJECTIVE

The aim of this study was to investigate whether the use of etoricoxib has negative effects on the perioperative outcome in colorectal surgery.

DESIGN

Complication data from an advanced medical database system were sampled prospectively, and patient records were reviewed retrospectively.

PATIENTS

All patients with elective colorectal surgery within an enhanced recovery after surgery protocol from 2008 to 2009 were selected.

INTERVENTION

The nonrandomized use of perioperative etoricoxib treatment was compared with a control group.

MAIN OUTCOME MEASURES

The primary outcome measured was the number of patients with postoperative complications according to the Dindo-Clavien classification.

RESULTS

One hundred one patients received etoricoxib treatment, whereas 104 did not. The patient groups were very comparable. We observed a significant increase in the number of patients with postoperative complications with etoricoxib treatment (43 vs 30 patients; 42.6% vs 28.8%, p = 0.041) due to an increase in patients with a major complication (Dindo-Clavien complication grade III-V: 22.8% vs 9.6%, p = 0.01). Patients with etoricoxib treatment and a complication needed a longer recovery period than patients with a complication in the control group (18 (17; 20) vs 14 (13; 15) days, p = 0.05). We observed an increased level of postoperative serum creatinine with etoricoxib treatment (105 (98; 112) vs 82 (78; 85), p = 0.003), which was more pronounced in patients with a complication (141 (127; 155) vs 91 (83; 98), p = 0.002; 25 vs 8 patients with serum creatinine >100 μmol/L, p = 0.008). In multivariate analysis, etoricoxib was identified as an independent risk factor for experiencing a major complication with a risk increase of approximately 2.5-fold (p = 0.03).

LIMITATIONS

This study was limited by the nonrandomized use of perioperative etoricoxib and the retrospective nature of its review of patient records.

CONCLUSIONS

Etoricoxib increased the number of patients with postoperative complications and should be considered carefully in colorectal surgery.

Nonsteroidal anti-inflammatory drugs and anastomotic dehiscence in bowel surgery: systematic review and meta-analysis of randomized, controlled trials

BACKGROUND

Nonsteroidal anti-inflammatory drugs are a key component of contemporary perioperative analgesia. Recent experimental and observational clinical data suggest an associated increased incidence of anastomotic dehiscence in bowel surgery.

OBJECTIVE

The aim of this study was to conduct a systematic review and meta-analysis of anastomotic dehiscence in randomized, controlled trials of perioperative nonsteroidal anti-inflammatory drugs.

DATA SOURCES

Published and unpublished trials in any language reported 1990 or later were identified by searching electronic databases, bibliographies, and relevant conference proceedings.

STUDY SELECTION

Trials of adults undergoing bowel surgery randomly assigned to perioperative nonsteroidal anti-inflammatory drugs or control were included. The number of patients with a bowel anastomosis and the incidence of anastomotic dehiscence had to be reported or be available from authors for the study to be included.

INTERVENTION

At least 1 dose of a nonsteroidal anti-inflammatory drug was given perioperatively within 48 hours of surgery.

MAIN OUTCOME MEASURES

The primary outcome measured was 30-day incidence of anastomotic dehiscence as defined by authors.

RESULTS

Six trials comprising 480 patients having a bowel anastomosis met inclusion criteria. In 4 studies, anastomotic dehiscence rates were higher in the intervention groups. Overall rates were 14/272 participants (5.1%) in intervention arms vs 5/208 (2.4%) in control arms. Peto OR was 2.16 (95% CI 0.85, 5.53; p = 0.11), and there was no heterogeneity between studies (I statistic 0%).

LIMITATIONS

Sizes of available trials were small, preventing firm conclusions and subset analysis of drugs of different cyclooxygenase specificity. A precise and consistent definition of anastomotic dehiscence was not used across trials.

CONCLUSIONS

A statistically significant difference in incidence of anastomotic dehiscence was not demonstrated. However, the Peto OR of 2.16 (0.85, 5.53) and lack of heterogeneity between trials suggest that this finding may be due to a lack of power of the available data rather than a lack of effect.

Carprofen for perioperative analgesia causes early anastomotic leakage in the rat ileum

Background

There is increasing evidence that perioperative use of NSAIDs may compromise the integrity of intestinal anastomoses. This study aims to characterize the negative effects of carprofen on early anastomotic healing in the rat ileum.

Results

In 159 male Wistar rats an anastomosis was constructed in the ileum. In experiment 1 eighty-four rats were divided over control and experimental groups, which received daily buprenorphine or carprofen, respectively, as an analgesic and were killed on day 1, 2 or 3 after surgery. In experiment 2 three groups of 15 rats received carprofen either immediately after surgery or with a delay of 1 or 2 days. Animals were killed after 3 days of carprofen administration. In experiment 3 three groups of 10 rats received different doses (full, half or quarter) of carprofen from surgery.

In significant contrast to buprenorphine, which never did so, carprofen induced frequent signs of anastomotic leakage, which were already present at day 1. If first administration was delayed for 48 hours, the leakage rate was significantly reduced (from 80 to 20%; p = 0.0028). Throughout the study, the anastomotic bursting pressure was lowest in animals who displayed signs of anastomotic leakage. Loss of anastomotic integrity did not coincide with reduced levels of hydroxyproline or increased activity of matrix metalloproteinases.

Conclusions

Carprofen interferes with wound healing in the rat ileum at a very early stage. Although the mechanisms responsible remain to be fully elucidated, one should be aware of the potential of NSAIDs to interfere with the early phase of wound repair.

Non-steroidal anti-inflammatory drugs in colorectal surgery: A risk factor for anastomotic complications?

In a recent article, Gorissen et al report on 795 patients with primary colorectal anastomosis operated on during the period 2008-2010 for different colorectal conditions at two centres. The leakage rate was significantly higher among patients who were administered non-steroidal anti-inflammatory drugs (NSAIDs) in the perioperative course. A dose-response relationship could also be traced, where longer NSAID use yielded a higher risk of anastomotic breakdown. However, as this study is observational in design, confounding by indication may be present and there is also a risk of residual confounding from unmeasured covariates. Moreover, the question whether different affinity for the cyclooxygenase enzyme is important in different NSAIDs seems to be largely unanswered. The results, conclusions and clinical relevance of the aforementioned study, including the possible effects of different types of NSAIDs, are discussed. While acknowledging that this study represents the best attempt so far in establishing the causal relationship between perioperative NSAID use and anastomotic leakage, the need for further research in this important area is underlined.

Risk of anastomotic leakage with non-steroidal anti-inflammatory drugs in colorectal surgery

BACKGROUND

With the implementation of multimodal analgesia regimens in fast-track surgery programmes, non-steroidal anti-inflammatory drugs (NSAIDs) are being prescribed routinely. However, doubts have been raised concerning the safety of NSAIDs in terms of anastomotic healing.

METHODS

Data on patients who had undergone primary colorectal anastomosis at two teaching hospitals between January 2008 and December 2010 were analysed retrospectively. Exact use of NSAIDs was recorded. Rates of anastomotic leakage were compared between groups and corrected for known risk factors in both univariable and multivariable analyses.

RESULTS

A total of 795 patients were divided into four groups according to NSAID use: no NSAIDs (471 patients), use of non-selective NSAIDs (201), use of selective cyclo-oxygenase (COX) 2 inhibitors (79), and use of both selective and non-selective NSAIDs (44). The overall leak rate was 9.9 per cent (10.0 per cent for right colonic, 8.7 per cent for left colonic and 12.4 per cent for rectal anastomoses). Known risk factors such as smoking and use of steroids were not significantly associated with anastomotic leakage. Stapled anastomosis was identified as an independent predictor of leakage in multivariable analysis (odds ratio (OR) 2.22, 95 per cent confidence interval 1.30 to 3.80; P = 0.003). Patients on NSAIDs had higher anastomotic leakage rates than those not on NSAIDs (13.2 versus 7.6 per cent; OR 1.84, 1.13 to 2.98; P = 0.010). This effect was mainly due to non-selective NSAIDs (14.5 per cent; OR 2.13, 1.24 to 3.65; P = 0.006), not selective COX-2 inhibitors (9 per cent; OR 1.16, 0.49 to 2.75; P = 0.741). The overall mortality rate was 4.2 per cent, with no significant difference between groups (P = 0.438).

CONCLUSION

Non-selective NSAIDs may be associated with anastomotic leakage.

Perioperative pain relief by a COX-2 inhibitor affects ileal repair and provides a model for anastomotic leakage in the intestine

The authors examined the potential of the cyclooxygenase 2 (COX-2) inhibitor carprofen to reproducibly induce anastomotic leakage. In experiment 1, an anastomosis was constructed in both ileum and colon of 20 rats, and they were given carprofen (5 mg/kg subcutaneously every 24 hours) or buprenorphine (0.02 mg/kg subcutaneously every 12 hours). In another 20 rats an anastomosis was constructed in either ileum or colon, and all received carprofen (experiment 2). Animals were sacrificed after 3 days. In experiment 1, the ileal dehiscence rate was 60% in the carprofen group and 0% in the buprenorphine group (P = .0108). Colonic anastomoses in both groups remained patent. In experiment 2, the anastomotic leakage rate was 80% in ileum and 0% in colon. Thus, COX-2 inhibitors can severely interfere with intestinal healing, particularly in the ileum. Perioperative administration of carprofen yields a unique model for anastomotic leakage, which allows translational research on the effectiveness of perisuture line reinforcement.

Effect of postoperative diclofenac on anastomotic healing, skin wounds and subcutaneous collagen accumulation: a randomized, blinded, placebo-controlled, experimental study

BACKGROUND

Retrospective studies have drawn attention to possible detrimental effects of non-steroidal anti-inflammatory drugs (NSAIDs) on the anastomotic leakage rate after colorectal resection. In this study, we examined the effects of the NSAID diclofenac on the breaking strength of an experimental colonic anastomosis and a skin incision as well as subcutaneous collagen accumulation.

METHODS

This was a randomized, blinded, placebo-controlled experimental study in 60 male Wistar rats treated with diclofenac 4 mg/kg/day or placebo. In each rat, a colonic anastomosis was performed and an expanded polytetrafluoroethylene (ePTFE) tube was placed subcutaneously. Incisional and anastomotic wound breaking strength and hydroxyproline content in the ePTFE tubes were measured 7 days after the operation.

RESULTS

We found no significant differences in any of the breaking strength measurements, but showed a median 38% reduction in hydroxyproline deposition as a result of diclofenac treatment (p = 0.03). In the placebo group, subcutaneous collagen deposition tended to correlate positively with skin incisional but negatively with anastomotic bio-mechanical strength.

CONCLUSION

Postoperative diclofenac treatment significantly inhibited collagen deposition in subcutaneous granulation tissue. Anastomotic strength and skin wound strength were not significantly affected. The ePTFE model is suitable for assessing the effect of various drugs on collagen formation and thus on wound healing.

Effect of celecoxib on proliferation, collagen expression, ERK1/2 and SMAD2/3 phosphorylation in NIH/3T3 fibroblasts

In the present study, the effects of celecoxib on proliferation, collagen expression, ERK1/2 and SMAD2/3 phosphorylation in NIH/3T3 fibroblasts were investigated. NIH/3T3 fibroblasts stimulated with fibroblast growth factor-2 (FGF-2) or transforming growth factor-β1 (TGF-β1) were examined in the presence of celecoxib. Proliferation was assessed by MTT assays; ERK1/2 expression and SMAD2/3 expression were assessed by quantitative RT-PCR and western blotting; ERK1/2 phosphorylation and SMAD2/3 phosphorylation were assessed by western blot analysis. The results indicated that celecoxib could suppress cell proliferation stimulated by FGF-2 (IC(50) FGF+group, 75±1.9μmol/l) and TGF-β1 (IC(50) TGF+group, 48±1.4μmol/l), by inhibiting ERK1/2 phosphorylation but not ERK1/2 expression. Celecoxib also suppressed collagen expression (0.35-fold COL3 and 0.43-fold COL1 at 320μmol/l celecoxib relative to the untreated control after stimulation with TGF-β1 for 3h, P<0.01), by inhibiting SMAD2/3 phosphorylation but not SMAD2/3 expression. The suppression of NIH/3T3 fibroblast proliferation and collagen expression upon stimulation by FGF-2 and TGF-β1 is likely a result of the inhibition of ERK1/2 and SMAD2/3 phosphorylation by celecoxib.

Risk of anastomotic leakage with use of NSAIDs after gastrointestinal surgery

PURPOSE

Analgesic regimes to avoid opioid-related adverse effects have been recommended in gastrointestinal surgery. Non-steroidal anti-inflammatory drugs (NSAIDs) are an important component of opioid sparing regimes in that these drugs indirectly reduce pain by inhibiting inflammation. Although beneficial for most surgical patients, animal studies and recent clinical studies suggest a harmful effect on new intestinal anastomoses by increasing the rate of leakage. NSAIDs may indirectly disturb anastomotic healing by inhibiting inflammation as an integrated part of the wound healing process in an early, critical phase after surgery.

METHODS

A literature review based on a structured search in PubMed of clinical and experimental studies investigating the effects of NSAIDs on anastomotic healing and leakage rates after intestinal surgery, as well as proposed mechanisms and effects studied in animal models.

RESULTS

Three recent observational cohort studies (accumulated n = 882) indicate an increased rate of anastomotic leakages (15-21%) associated with cyclooxygenase-2 (COX-2) selective NSAIDs after intestinal surgery compared to the leakage rates in controls or historical cohorts (1-4%). Three prospective studies on related topics contain relevant data on NSAIDs and are compared to these studies. Several experimental animal studies support an increased risk for anastomotic leakage with the use of NSAIDs.

CONCLUSION

The reported effects of NSAIDs on anastomotic healing suggest an increased risk for leakage. A better understanding of the complex interactions of NSAID-induced inhibition on anastomotic healing is a prerequisite for the safe use of NSAIDs. Until more data are available, a careful use of NSAIDs may be warranted in gastrointestinal anastomotic surgery.

The effect of β-adrenergic blockade and COX-2 inhibition on healing of colon, muscle, and skin in rats undergoing colonic anastomosis

Abstract. Objective: COX inhibitors and b-adrenergic blockers were recently shown to reduce cancer progression in animal models through various mechanisms. These include the prevention of immune suppression during the critical perioperative period, and the preclusion of direct promoting effects of catecholamines and prostaglandins on malignant tissue growth. To assess the safety of such pharmacological treatments in the context of oncologic surgery, the current study evaluates wound healing efficacy in the skin, muscle, and colon tissues in rats undergoing colonic anastomosis. Methods: F344 rats were treated daily with a COX-2 inhibitor (etodolac), a b-adrenergic blocker (propranolol), both drugs or vehicles. All rats underwent skin punch biopsy, and half were also subjected to laparotomy and colonic anastomosis. Tensile strength of the abdominal wall and colonic bursting pressure were assessed on Days 3, 7, and 30 postoperatively, and skin biopsy site healing was scored on Days 2, 4, and 6 postoperatively. Results: None of the drug treatments produced any deleterious effects along the expected course of tissue healing. On Day 30, colon bursting pressure showed an abnormal strengthening in animals undergoing anastomosis compared to non-operated animals, across all drug treatments. This abnormal strengthening was attenuated by etodolac. In the skin, surgery reduced healing rate, irrespective of drug treatments. Conclusions: Effective doses of etodolac and propranolol caused no negative effects on wound healing processes in rats. The apparent safety of such treatments, together with their potential clinical benefits, suggests the incorporation of these treatments in oncologic patients undergoing curative tumor resection.

Colonic anastomotic healing in the context of altered macrophage function and endotoxemia

PURPOSE

Prevention of perioperative activation of intestinal muscularis macrophages is a promising intervention to avoid post-traumatic gastrointestinal tract dysfunction. However, impaired macrophage function could have deleterious consequences on anastomotic healing, especially in complications aggravating the healing process itself, such as infectious problems either as preexisting local inflammation or infection (e.g., complicated diverticulitis) or endotoxemia due to early postoperative infections (e.g., pneumonia). Aim of this study was to investigate colonic anastomotic healing in macrophage-depleted mice in the presence of endotoxemia.

METHODS

Colonic anastomoses were performed, and mice were randomized into six groups (wild type; wild type with endotoxemia; pharmacological depletion of macrophages; pharmacological depletion with endotoxemia; genetically conditioned within the gut muscularis macrophage-deficient osteopetrotic mice; osteopetrotic mice with endotoxemia). Anastomotic tissues were removed 2, 5, and 10 days after surgery and used for functional, histological, biochemical, and molecular investigations.

RESULTS

After pharmacological pretreatment, an almost complete depletion of macrophages was found in the muscularis up to 24 h postoperatively. Bursting pressure was significantly lower than 10 days after anastomotic procedure in osteopetrotic mice during endotoxemia, in marked contrast to transient pharmacologically macrophage-depleted mice. Pharmacological depletion during endotoxemia did not affect hydroxyproline concentration. Finally, in osteopetrotic mice during endotoxemia, collagen-3 expression was significantly lower compared to controls.

CONCLUSIONS

In our current model, we demonstrate that perioperative pharmacological macrophage depletion and inactivation transiently diminishes muscularis macrophages and does not affect intestinal anastomotic healing in the presence of endotoxemia. However, a long-lasting macrophage absence or dysfunction impairs anastomotic healing and could be a risk factor for postoperative anastomotic leakage.

Effect of beta blocker combined with COX-2 inhibitor on colonic anastomosis in rats

PURPOSE

Pharmacologic modulation of the perioperative physiologic stress response, using the beta-blocker propranolol, combined with the COX-2 inhibitor etodolac, has been shown to reduce metastatic spread and increase survival rates following surgery for primary tumor excision in rodents. Prior to implantation of this pharmacological approach in clinical trials in patients with colon cancer, the safety of this technique has to be evaluated. This study assessed the effects of these drugs on the healing of colonic anastomosis in rats.

METHODS

Forty-eight F344 rats were divided into two groups, which were given seven daily subcutaneous injections of either vehicle, or propranolol (up to 1.2 mg/kg/day) combined with etodolac (12.5 mg/kg/day), starting the day before surgery. Each animal underwent laparotomy, colotomy of the descending colon, and anastomosis. Anastomotic leak rate and bursting pressure were compared at 1 week after the operation. The harvested anastomosis was histologically assessed for wound healing parameters.

RESULTS

Forty-three rats survived the operation and were eligible for analysis at 1 week. No significant difference in survival, anastomotic leakage, or bursting pressure was found between animals that received propranolol and etodolac versus those receiving vehicle (drugs 179 mmHg ± 45.4; vehicle 187 mmHg, SD ± 35.0, p = 0.54). Histologic assessment of fibrosis, necrosis, cell infiltration, and tissue reaction zone did not differ between the two groups.

CONCLUSIONS

Perioperative administration of propranolol and etodolac seems safe in colon operations in rats and does not affect anastomotic failure or colon healing.

Cyclo-oxygenase 2 inhibitors and the risk of anastomotic leakage after fast-track colonic surgery

BACKGROUND

Anastomotic leakage occurs after 3-6 per cent of colonic resections. The influence of analgesic agents is largely unknown. This study determined the rate of anastomotic leakage in a series of patients who had colonic surgery over a 9-year period with or without use of a cyclo-oxygenase inhibitor for postoperative analgesia.

METHODS

Patients with anastomotic leakage following a standard fast-track procotol between April 1997 and May 2006 were identified from a prospective, consecutive database. During this period there were two changes in perioperative management: cessation of preoperative oral bowel preparation in August 2002 and the use of celecoxib for postoperative analgesia between May 2003 and November 2004. Rates of anastomotic leakage during the various periods were determined and compared.

RESULTS

Some 28 (5.6 per cent) of 502 patients had an anastomotic leak. The incidence of leakage increased significantly during the period of celecoxib use (15.1 per cent), versus 3.3 and 1.5 per cent respectively before and after celecoxib use (P < 0.001). Leakage rates were similar with or without oral bowel preparation (3.5 versus 1.7 per cent respectively; P = 0.346) when celecoxib was not used.

CONCLUSION

A detrimental effect of celecoxib on anastomotic healing is suggested, and requires further evaluation.

Effects of cyclooxygenase inhibition on anastomotic healing following large bowel resection in a rabbit model--a randomized, blinded, placebo-controlled trial

PURPOSE

We performed an experimental study in a rabbit model to investigate the effects of a selective Cox-2 inhibitor (Valdecoxib) on anastomotic healing following large bowel resection after 1 week.

MATERIALS AND METHODS

Eighty New Zealand white rabbits were randomized into four groups and underwent a colon resection with end-to-end anastomosis. Group 1 (n = 20) was treated with Valdecoxib, group 2 with Metamizole (Novalgin), group 3 with Resveratrol (specific Cox-1 inhibitor), or a placebo vehicle with similar volume (group 4). Anastomotic healing was tested at the seventh postoperative day by measurement of the bursting pressure in vitro. Immunohistochemical staining of the anastomotic site was performed with polyclonal antibodies (CD31).

RESULTS

There were no significant differences in anastomotic dehiscence, bursting pressure, or vessel density between the treatment and control groups.

CONCLUSION

The application of Valdecoxib does not influence anastomotic healing or new vessel formation in the anastomotic region following large bowel resection.

Supplementation with High-Dose Ascorbic Acid Improves Intestinal Anastomotic Healing

BACKGROUND/AIM

Ascorbic acid modulates tissue healing but the value of ascorbic acid supplementation during anastomotic healing remains unclear. We examined the role of ascorbic acid treatment in experimental intestinal resection.

METHODS

Male Wistar albino rats (n = 30) were divided into three groups: sham treatment (group 1), and daily ascorbic acid treatment with 100 mg/kg (group 2) or 200 mg/kg (group 3) via the intramuscular route. Following sacrifice on the 7th postoperative day, bursting pressure of the anastomoses was measured. Hydroxyproline assessment and histological analysis were carried out.

RESULTS

The bursting pressure values of groups 2 (171.4 +/- 4.3 mm Hg) and 3 (196.4 +/- 2.2 mm Hg) were higher than that of group 1 (139.1 +/- 4.1 mm Hg; p < 0.05). In addition, the hydroxyproline level of group 3 (249.2 +/- 25.1 microg/mg) was higher than that of groups 1 (157.9 +/- 14.9 microg/mg) and 2 (187.9 +/- 14.8 microg/mg; p < 0.05). The histopathological scores indicated improved healing in groups 3 (6.0 +/- 0.2) and 2 (4.4 +/- 0.4), compared to group 1 (2.7 +/- 0.3; p < 0.05).

CONCLUSION

In the present study, supraphysiologic doses of ascorbic acid improved anastomotic healing. Therefore, vitamin C supplementation poses as a beneficial treatment in the context of collagen accumulation, inflammatory response, and anastomotic strength. However, the clinical value of high-dose ascorbic acid supplementation in the clinical setting is yet to be established.

Everolimus interferes with healing of experimental intestinal anastomoses

BACKGROUND

Although clinical data suggest its existence, little is known about the effect of rapamycin derivatives on wound repair. This study aims to delineate the influence of the mammalian target of rapamycin inhibitor everolimus on wound healing in the rat intestine.

METHODS

Four groups of 26 male Wistar rats received everolimus in daily oral dosages of 0 (controls), 0.5 (group E-0.5), 1.0 (group E-1), and 3.0 (group E-3) mg/kg every 24 hours, respectively, starting four hours before the operation until killing. After resection of 1-cm segments of colon and ileum, intestinal anastomoses were constructed. The animals were killed at days three or seven after operation. Wound healing was assessed by mechanical (bursting pressure, breaking strength), biochemical (collagen content, gelatinase activity), and histologic parameters.

RESULTS

No differences between groups were recorded for any of the parameters on day three. On day seven, a dose-dependent reduction in breaking strength (P<0.05) was measured. The largest effects were found in group E-3 in which the breaking strength was reduced by 56% and 73% in colonic and ileal anastomoses, respectively. A similar pattern was observed with the bursting pressure. Loss of strength was accompanied by a reduction in hydroxyproline content and by a lessened collagen deposition in the wound area but not by an increased gelatinase activity. No further histologic abnormalities were found.

CONCLUSION

Everolimus causes a massive reduction in anastomotic strength such as normally observed in the proliferative phase of repair. The data suggest this to be caused by an impaired deposition of collagen in the anastomotic area.

Nonsteroidal antiinflammatory drugs and the small intestine

PURPOSE OF REVIEW

The small intestine may be a more common site for nonsteroidal antiinflammatory drug toxicity than the gastroduodenal mucosa. Two-thirds of regular nonsteroidal antiinflammatory drug users develop subclinical small bowel enteropathy. This review highlights this emerging issue in patients requiring antiinflammatory drugs.

RECENT FINDINGS

Nonsteroidal antiinflammatory drug enteropathy is a stepwise process involving direct mucosal toxicity, mitochondrial damage, breakdown of intercellular integrity, enterohepatic recirculation and neutrophil activation by luminal contents including bacteria. Unlike upper gastrointestinal toxicity, cyclooxygenase-mediated mechanisms are probably less important. Newer imaging modalities such as capsule endoscopy studies demonstrate nonsteroidal antiinflammatory drug-induced small bowel erosions, but the clinical implications are unclear.

SUMMARY

Nonsteroidal antiinflammatory drug toxicity to the small intestine is common. Useful research tools have been developed to indirectly measure intestinal inflammation and permeability, but these are not generally available to the clinician, although enteroscopy and capsule endoscopy can be illuminating. Anaemia or hypoalbuminaemia are useful indications of nonsteroidal antiinflammatory drug enteropathy. Cessation of the drug would be the preferred option, alternatively there are experimental data to support the use of sulphasalazine and metronidazole. Animal models are unravelling new mechanisms for mucosal toxicity beyond the cyclooxygenase model, including mucosal oxidative injury and nitric oxide mediated pathways.