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Background and aims: Bariatric surgery is increasingly performed worldwide to treat morbid obesity and is also known as metabolic surgery to reflect its beneficial metabolic effects especially with respect to improvement in type 2 diabetes. Understanding surgical weight loss mechanisms and metabolic modulation is required to enhance patient benefits and operative outcomes. Methods: The authors applied a parallel and statistically integrated bacterial profiling and metabonomic approach to characterise Roux-en-Y gastric bypass (RYGB) effects in a non-obese rat model. Results: Substantial shifts of the main gut phyla towards higher concentrations of Proteobacteria (52-fold), specifically Enterobacter hormaechei, are shown. Low concentrations of Firmicutes (4.5-fold) and Bacteroidetes (twofold) in comparison with sham-operated rats were also found. Faecal extraction studies revealed a decrease in faecal bile acids and a shift from protein degradation to putrefaction through decreased faecal tyrosine with concomitant increases in faecal putrescine and diaminoethane. Decreased urinary amines and cresols were found and indices of modulated energy metabolism were demonstrated after RYGB, including decreased urinary succinate, 2-oxoglutarate, citrate and fumarate. These changes could also indicate renal tubular acidosis, which is associated with increased flux of mitochondrial tricarboxylic acid cycle intermediates. A surgically induced effect on the gut–brain–liver metabolic axis is inferred from modulated faecal γ-aminobutyric acid and glutamate. Conclusion: This profound co-dependence of mammalian and microbial metabolism, which is systematically altered after RYGB surgery, suggests that RYGB exerts local and global metabolic effects. The effect of RYGB surgery on the host metabolic–microbial cross-talk augments our understanding of the metabolic phenotype of bariatric procedures and can facilitate enhanced treatments for obesity-related diseases.

Introduction Emergency surgery for colorectal cancer (CRC) conveys high postoperative morbidity and mortality. The aim of this study is to identify patient groups at high risk of emergency presentation and quantify their overall survival. Method All patients diagnosed with colorectal cancer between the year 1997–2011 were identified from the Hospital Episode Statistics (HES) database. Logistic regression analyses were undertaken to identify patient groups at risk of undergoing emergency surgery for colorectal cancer at first presentation. Survival plots using multivariable cox proportional hazard analyses were generated. Results Over this time period, 286,591 patients underwent resection for CRC, 69,718 (24.3%) of which were as emergencies. While, the overall rate of emergency CRC resection has significantly decreased from 29.5% in 1997 to 16.5% in 17.2% in 2011 (p 79 yrs old) are 55% more likely to require emergency surgery (OR 1.55, CI: 1.50–1.60, p Conclusion Whilst the overall rate of emergency colorectal cancer surgery is reducing, elderly patients, those from a socioeconomically deprived background and Black Afro-Caribbean patients remain at high risk of emergency attendance. Post-operative morbidity and mortality remains high in emergency presenters and 5-year survival in this patient group remains poor. Targeting screening of these high-risk patient groups is essential to reduce the number of patients attending as an emergency further. Disclosure of interest None Declared.

Introduction Population-based bowel cancer screening has resulted in increasing numbers of patients with T1 colonic neoplasia. The need for colectomy in this group is questioned due to the low risk of lymphatic spread and increased treatment morbidity. This study examined the quality-of-life benefits and risks of local excision compared with results after colectomy, for low- and high-risk T1 colonic cancer. Method Decision analysis using a Markov simulation model was performed: patients were managed with either local excision (advanced therapeutic endoscopy) or colectomy. Lesions were considered high-risk according to accepted national guidelines. Probabilities and utilities were derived from published data. Hypothetical cohorts of 65- and 80-year-old, fit and unfit patients, with low- or high-risk T1 colonic cancer were studied. The primary outcome was quality-adjusted life expectancy (QALE) in life-years (QALYs). Results In low-risk T1 colonic neoplasia, local excision increases QALE by 2.72 QALYS for fit 65-year olds (15.5% increase over surgery) and by 0.93 for unfit 80-year-olds (20.9% increase). For high-risk T1 cancers, the QALE benefit for local excision is 1.82 QALYs for fit 65-year-olds (10.5% improvement) and 0.82 for unfit 80-year-olds (18.6% improvement). In sensitivity analysis, colectomy was only preferred for 65-year-old patients, when risk of recurrence following local excision exceeded 17.3%. Conclusion Under a wide range of assumptions, for all patient cohorts, local excision is a reasonable treatment option for both low- and high-risk T1 colonic cancer. Exploration of methods to facilitate local excision of T1 colonic neoplasia appears warranted. Disclosure of interest None Declared.

Introduction Colorectal cancer (CRC) patients with Ulcerative Colitis (UC) and Crohn’s Disease (CD) can be challenging to manage in the perioperative period. The aim of this study is to examine differences between Inflammatory Bowel Disease (IBD) and sporadic CRC patients in terms of the emergency admission rates, length of stay and post operative complications. Method A national study was carried out using the Hospital Episode Statistics (HES) database between the years of 1997 to 2012. Multivariable binary logistic regression was undertaken to determine whether IBD was independently associated with the development of a postoperative complication. Results During the study time period, 286,591 patient underwent colorectal cancer resection, 0.8% of which (n = 2,322) had IBD. A greater proportion of IBD patients underwent a colorectal cancer resection as an emergency than sporadic patients (UC 25.1%, CD 34.7% and sporadic 24.3%, p Conclusion IBD patients, particularly Crohn’s patients commonly have their colorectal cancer resected in an emergency setting. IBD patients are more likely to require 30-day re-intervention, irrespective of other factors. A multi-disciplinary team approach incorporating surgeons, gastroenterologists, anaesthetists and radiologists is essential in the management of these complex patients in the peri-operative period Disclosure of interest None Declared.

Introduction Trends towards shortening hospital stay through day case surgery and enhanced recovery mean that postoperative venous thromboembolism (VTE) may increasingly occur following hospital discharge. However, population rates of postoperative VTE cannot be measured from hospital databases alone, as they do not capture information outside of the hospital setting. The National Institute for Health and Care Excellence has suggested the use of linked hospital and primary care data to gain a better understanding of rates of hospital care-related VTE, 1 however, data for surgical patients is lacking. Method Ninety-day in-hospital and post-discharge VTE and mortality were evaluated in twelve general surgical procedures performed from 1997 to 2012 using linked Clinical Practice Research Datalink (CPRD), Hospital Episodes Statistics (HES), Office of National Statistics (ONS) and National Cancer Intelligence Network (NCIN) databases. The proportion of VTE captured in each database and risk factors for VTE and mortality were evaluated. Results 168005 operations over fifteen years were evaluated. There were 981 (0.58%) VTE events recorded after 90 days postoperatively. Different datasets recorded variable rates of VTE. CPRD recorded 56.0% (549/981), HES recorded 66.3% (650/981) and ONS recorded 8.3% (81/981) of all recorded VTE. For VTE recorded in two databases, 28.3% (278/981) were in HES and CPRD and 2.1% (21/981) in HES and ONS. Overall VTE rate ranged between 0.08% (14/17554, 3.2/1000 patient years) following haemorrhoidectomy to 2.92% (61/2091, 118.3/1000 patient years) following oesophagogastrectomy. Predictors of VTE included emergency surgery (OR = 1.91), age (OR = 1.02), body mass index (OR = 1.03), previous VTE (OR = 8.07), length of stay (OR = 1.00) and cancer stages II (OR = 1.38), III (OR = 1.50) and IV (OR = 1.63). Major organ resections had the greatest odds of VTE. The frequency of in-hospital VTE ranged from 76.4 to 288.9/1000 person years, while post-discharge VTE ranged from 2.6 to 82.1/1000 patient years. Both in-hospital (OR = 2.07) and post-discharge (OR = 4.03) VTE independently predicted 90-day mortality (p Conclusion A large proportion of postoperative VTE were detected in the primary care setting. Evaluation of linked databases is a useful way of measuring postoperative VTE at population level. These resources identified substantial harm from post-discharge VTE following general surgical procedures. Disclosure of interest None Declared. Reference National Institute for Health and Care Excellence. Venous thromboembolism in patients admitted to hospital. Guideline No. 92, 2010

Introduction Trends towards early hospital discharge mean that complications such as venous thromboembolism (VTE) may increasingly occur in the primary care setting. Guidelines recommend thromboprophylaxis after hospital discharge in patients undergoing gastrointestinal cancer resection. However factors other than the presence of malignancy may prolong VTE risk. Previous studies have shown increased VTE risk with reoperation. The combined effect of VTE and reoperation on mortality has not been reported. Method Thirty-day reoperation, 90-day VTE and 90-day mortality was measured using linked Clinical Practice Research Datalink (CPRD), Hospital Episodes Statistics (HES), Office of National Statistics (ONS) and National Cancer Intelligence Network databases. The effect of different types of reoperation on VTE risk adjusted for length of hospital stay and other short-term complications was evaluated in adults undergoing one of seven gastrointestinal surgical procedures. The combined effect of VTE and reoperation on mortality was evaluated in benign and cancer patients separately. Results 76334 procedures over fifteen years were evaluated. Thirty-day reoperation was recorded in 3.18% (2426/76334) of procedures. There were 721/76334 (0.94%) VTE events recorded after 90 days of surgery (0.51% - 294/58036 in procedures for benign disease, 2.33% - 427/18298 in procedures for cancer). Over half (57.7%, 416/721) of VTE were recorded after hospital discharge. Reoperation was an independent predictor of 90-day VTE in benign (OR=1.88, p Conclusion Reoperation increased VTE risk in patients undergoing gastrointestinal surgery for benign conditions, while reoperation and VTE acted synergistically to increase mortality in patients undergoing surgery for cancer. Reoperation was therefore associated with significant harm from VTE extending into the out-patient setting, which may infer the need for additional thromboprophylaxis in some patients. Disclosure of interest None Declared.

Introduction Anastomotic leakage is generally assumed to occur from approximately 5 days after surgery unless there has been a technical error in anastomotic construction. In order to investigate whether this assumption is correct, clinical changes associated with anastomotic leakage were studied in a homogeneous group of patients. Method Individuals were included from a prospectively collected database of patients undergoing laparoscopic total colectomy and ileorectal anastomosis (LTC and IRA) for familial adenomatous polyposis (FAP) between 2006–2013 at a single institution. Patients suffering anastomotic leakage (case group) were compared with controls that did not leak. These controls were selected as the consecutive case before and after each leak case (2 controls for each case). Panel data was collected as repeated measures of continuous post-operative parameters and time-series regression performed using a double subscript structure. A generalised least squares multivariate approach was applied in a random effects setting to calculate correlations for observations with the dependent outcome of anastomotic leak. Regression calculations were performed according to individual observations at each time point to identify outcome correlations. Results Data from 95 patients who underwent LTC and IRA for FAP between 2006 and 2013 was available for analysis. All operations were performed laparoscopically within an enhanced recovery programme. 10 patients (10.5%) developed International Classification Grade C leakage (requiring laparotomy), with a mean time to diagnosis of 7.5 +/- 2.6 days. The mean age of the 10 leak patients and 20 controls was 31.9 (+/-17.0) years. There was no significant difference between groups in age, sex, ASA grade, physiology, and operative score. Multivariate analysis of physiological parameters demonstrated a significant difference between leak patients and controls in respiratory rate, urine output, diastolic blood pressure, and heart rate within 48 h of operation. Biochemical parameters, including white cell count, neutrophil count, albumin, and C-reactive protein, did not differ significantly. Conclusion Following anastomotic leakage, significant changes in physiological parameters are identifiable within 48 h of surgery. Leakage may occur earlier than has previously been thought and identification may provide opportunities for earlier intervention in order to improve outcome. Disclosure of interest None Declared.

Introduction Ulcerative Colitis (UC) and Crohn’s Disease (CD) are both implicated as risk factors for the development of colorectal cancer (CRC). It is unclear if this patient group has a poor survival after diagnosis. The aim of this study is to determine survival in Inflammatory Bowel Disease (IBD) associated CRC compared with sporadic CRC. Method Patients with a diagnosis of both CRC and IBD were identified from a national administrative dataset (Hospital Episode Statistics – HES). Multivariable cox proportional hazards regression analyses (adjusting for gender, age, medical comorbidity, mode of admission, operation type, chemotherapy) were used to determine survival differences. Results A total of 286,591 patients underwent surgery for CRC in England, between 1997–2012: 0.5% (n = 1,546) had UC and 0.3% (n = 776) had CD. Patients with IBD were diagnosed with CRC at a significantly younger age compared with sporadic patients (UC median age 64, CD median age 63, sporadic median age 71, p Conclusion IBD associated CRC develops at a younger age than sporadic CRC with poorer long-term survival, particularly for patients with CD. The reasons for shortened survival amongst IBD patients who develop CRC are unclear. Disclosure of interest None Declared.

Introduction Elderly patients are at increased risk of death following surgery for colorectal cancer, even in the elective setting. This national study aims to examine the relationship between patient selection for laparoscopic resection and survival in an elderly cohort. Method Elderly patients (80 years and over) undergoing elective colorectal cancer resection between the years 2001–2011 were identified from the Hospital Episode Statistics (HES) database. Mortality data from Office for National Statistics (ONS) were obtained. Survival analyses using multivariable cox proportional hazard regression were carried. Confounding variables such as gender, medical comorbidity, type of operation and chemotherapy were adjusted for. Results In the time period, 5,398 elderly patients underwent elective colorectal cancer resection, of which 1,479 patients (27.4%) underwent laparoscopic resection. The mean 5-year survival in the open group was 41.0 months (95% CI 40.3–41.7) in the open group compared with 52.3 months (95% CI 51.2–53.3) in the laparoscopic group (p Conclusion Laparoscopic resections for colorectal cancer confer a survival advantage beyond the immediate post operative period in elderly patients. Offering this high-risk patient group elective laparoscopic resections in experienced units could help deliver better outcomes. Disclosure of interest None Declared.

Introduction Imaging modalities such as endoanal ultrasound or MRI can be useful preoperative adjuncts prior to the appropriate surgical intervention for perianal fistulas. We present a systematic review of published literature comparing endoanal ultrasound with MRI for the assessment of idiopathic and Crohn9s perianal fistulas. Methods A meta-analysis was performed to obtain pooled values for specificity and sensitivity. Electronic databases were searched from January 1970 to October 2010 for published studies. Results Four studies were used in our analysis. There were 241 fistulas in the ultrasound group and 240 in the magnetic resonance group. The combined sensitivity and specificity of magnetic resonance for fistula detection were 0.87 (95% CI 0.63 to 0.96) and 0.69 (95% CI 0.51 to 0.82). There was a high degree of heterogeneity between studies reporting on MRI sensitivity (df=3, I 2 =93%). This compares to a sensitivity and specificity for endoanal ultrasound of 0.87 (95% CI 0.70 to 0.95) and 0.43 (95% CI 0.21 to 0.69) respectively. There was a high degree of heterogeneity between studies reporting on EAUS sensitivity (df=3, I 2 =92%). Conclusion From the available literature, the summarised performance characteristics for MRI and EAUS demonstrate comparable sensitivities at detecting perianal fistulas, although the specificity for MRI was higher than that for EAUS. Both specificity values are however considered to be diagnostically poor. The high degree of data heterogeneity and the shortage of applicable studies precludes any firm conclusions being made for clinical practice. Future trials with improved study design (including prospective data collection and consideration of verification bias) may help to further clarify the role of MRI in the assessment and treatment response monitoring of perianal fistulas (particularly in patients with Crohn9s disease). Competing interests None declared.