Artificial intelligence in surgery.

Artificial intelligence (AI) is rapidly emerging in healthcare, yet applications in surgery remain relatively nascent. Here we review the integration of AI in the field of surgery, centering our discussion on multifaceted improvements in surgical care in the preoperative, intraoperative and postoperative space. The emergence of foundation model architectures, wearable technologies and improving surgical data infrastructures is enabling rapid advances in AI interventions and utility. We discuss how maturing AI methods hold the potential to improve patient outcomes, facilitate surgical education and optimize surgical care. We review the current applications of deep learning approaches and outline a vision for future advances through multimodal foundation models.

Risk prediction algorithms for prolonged postoperative ileus: A systematic review.

AIM: Prolonged postoperative ileus (PPOI) is common and is associated with a significant healthcare burden. Previous studies have attempted to predict PPOI clinically using risk prediction algorithms. The aim of this work was to systematically review and compare risk prediction algorithms for PPOI following colorectal surgery. METHOD: A systematic literature search was conducted using MEDLINE, Embase, Web of Science and CINAHL Plus. Studies that developed and/or validated a risk prediction algorithm for PPOI in adults following colorectal surgery were included. Data were collected on study design, population and operative characteristics, the definition of PPOI used and risk prediction algorithm design and performance. Quality appraisal was assessed using the PROBAST tool. RESULTS: Eleven studies with 87 549 participants were included in our review. Most were retrospective, single-centre analyses (6/11, 55%) and rates of PPOI varied from 10% to 28%. The most commonly used variables were sex (8/11, 73%), age (6/11, 55%) and surgical approach (5/11, 45%). Area under the curve ranged from 0.68-0.78, and only three models were validated. However, there was significant variation in the definition of PPOI used. No study reported sensitivity, specificity or positive/negative predictive values. CONCLUSION: Currently available risk prediction algorithms for PPOI appear to discriminate moderately well, although there is a lack of validation data. Future studies should aim to use a standardized definition of PPOI, comprehensively report model performance and validate their findings using internal and external methodologies.

Characterization of gastric dysfunction after fundoplication using body surface gastric mapping.

BACKGROUND: Adverse gastric symptoms persist in up to 20% of fundoplication operations completed for gastroesophageal reflux disease, causing significant morbidity and driving the need for revisional procedures. Noninvasive techniques to assess the mechanisms of persistent postoperative symptoms are lacking. This study aimed to investigate gastric myoelectrical abnormalities and symptoms in patients after fundoplication using a novel noninvasive body surface gastric mapping (BSGM) device. METHODS: Patients with a previous fundoplication operation and ongoing significant gastroduodenal symptoms and matched controls were included. BSGM using Gastric Alimetry (Alimetry Ltd) was employed, consisting of a high-resolution 64-channel array, validated symptom-logging application, and wearable reader. RESULTS: A total of 16 patients with significant chronic symptoms after fundoplication were recruited, with 16 matched controls. Overall, 6 of 16 patients (37.5%) showed significant spectral abnormalities defined by unstable gastric myoelectrical activity (n = 2), abnormally high gastric frequencies (n = 3), or high gastric amplitudes (n = 1). Patients with spectral abnormalities had higher Patient Assessment of Upper Gastrointestinal Disorders-Symptom Severity Index scores than those of patients without spectral abnormalities (3.2 [range, 2.8-3.6] vs 2.3 [range, 2.2-2.8], respectively; P = .024). Moreover, 7 of 16 patients (43.8%) had BSGM test results suggestive of gut-brain axis contributions and without myoelectrical dysfunction. Increasing Principal Gastric Frequency Deviation and decreasing Rhythm Index scores were associated with symptom severity (r > .40; P < .05). CONCLUSION: A significant number of patients with persistent postfundoplication symptoms displayed abnormal gastric function on BSGM testing, which correlated with symptom severity. Our findings advance the pathophysiologic understanding of postfundoplication disorders, which may inform diagnosis and patient selection for medical therapy and revisional procedures.

Variation in the definition of 'failure to rescue' from postoperative complications: a systematic review and recommendations for outcome reporting.

BACKGROUND: Failure to rescue is the rate of death amongst patients with postoperative complications and has been proposed as a perioperative quality indicator. However, variation in its definition has limited comparisons between studies. We systematically reviewed all surgical literature reporting failure to rescue rates and examined variations in the definition of the 'numerator,' 'denominator,' and timing of failure to rescue measurement. METHODS: Databases were searched from inception to 31 December 2022. All studies reporting postoperative failure to rescue rates as a primary or secondary outcome were included. We examined the complications included in the failure to rescue denominator, the percentage of deaths captured by the failure to rescue numerator, and the timing of measurement for complications and mortality. RESULTS: A total of 359 studies, including 212,048,069 patients, were analyzed. The complications included in the failure to rescue denominator were reported in 295 studies (82%), with 131 different complications used. The median number of included complications per study was 10 (interquartile range 8-15). Studies that included a higher number of complications in the failure-to-rescue denominator reported lower failure-to-rescue rates. Death was included as a complication in the failure to rescue the denominator in 65 studies (18%). The median percentage of deaths captured by the failure to rescue calculation when deaths were not included in the denominator was 79%. Complications (52%) and mortality (40%) were mostly measured in-hospital, followed by 30-days after surgery. CONCLUSION: Failure to rescue is an important concept in the study of postoperative outcomes, although its definition is highly variable and poorly reported. Researchers should be aware of the advantages and disadvantages of different approaches to defining failure to rescue.

"Failure to Rescue" following Colorectal Cancer Resection: Variation and Improvements in a National Study of Postoperative Mortality.

OBJECTIVE: To examine variation in "failure to rescue" (FTR) as a driver of differences in mortality between centres and over time for patients undergoing colorectal cancer surgery. BACKGROUND: Wide variation exists in postoperative mortality following colorectal cancer surgery. FTR has been identified as an important determinant of variation in postoperative outcomes. We hypothesized that differences in mortality both between hospitals and over time are driven by variation in FTR. METHODS: A national population-based study of patients undergoing colorectal cancer resection from 2010 to 2019 in Aotearoa New Zealand was conducted. Rates of 90-day FTR, mortality, and complications were calculated overall, and for surgical and nonoperative complications. Twenty District Health Boards (DHBs) were ranked into quartiles using risk- and reliability-adjusted 90-day mortality rates. Variation between DHBs and trends over the 10-year period were examined. RESULTS: Overall, 15,686 patients undergoing resection for colorectal adenocarcinoma were included. Increased postoperative mortality at high-mortality centers (OR 2.4, 95% CI 1.8-3.3) was driven by higher rates of FTR (OR 2.0, 95% CI 1.5-2.8), and postoperative complications (OR 1.4, 95% CI 1.3-1.6). These trends were consistent across operative and nonoperative complications. Over the 2010 to 2019 period, postoperative mortality halved (OR 0.5, 95% CI 0.4-0.6), associated with a greater improvement in FTR (OR 0.5, 95% CI 0.4-0.7) than complications (OR 0.8, 95% CI 0.8-0.9). Differences between centers and over time remained when only analyzing patients undergoing elective surgery. CONCLUSION: Mortality following colorectal cancer resection has halved over the past decade, predominantly driven by improvements in "rescue" from complications. Differences in FTR also drive hospital-level variation in mortality, highlighting the central importance of "rescue" as a target for surgical quality improvement.

Hyperactive Distal Colonic Motility and Recovery Patterns Following Right Colectomy: A High-Resolution Manometry Study.

BACKGROUND: Postoperative ileus results in morbidity, prolonged hospitalization, and increased health care expenditure. However, the underlying abnormalities in motility remain poorly understood. Recent high-resolution manometry studies demonstrated that the distal colon becomes hyperactive with a cyclic motor pattern postoperatively, but they did not track this activity beyond 16 hours after surgery. OBJECTIVE: This study used high-resolution manometry to evaluate distal colonic motility during the first 4 days after right-sided colectomy. DESIGN: An observational study of perioperative high-resolution colonic manometry using a 36-sensor catheter with 1-cm resolution. SETTING: A single tertiary hospital. PATIENTS: Adult patients undergoing elective laparoscopic or open right-sided colonic resection. MAIN OUTCOME MEASURES: Occurrence of distal colonic motor patterns during the perioperative period, defined according to a published classification system. Clinical markers of gut recovery included time to first stool, oral diet, and prolonged postoperative ileus. RESULTS: Seven patients underwent perioperative manometry recordings. Hyperactive cyclic motor patterns emerged intraoperatively and peaked in the first 12 hours postoperatively, occupying 81.8% ± 3.9% of the recording. This gradually returned to normal during the first 4 days, reaching 19.0% ± 4.4% ( p = 0.002). No patient had a bowel movement before this hyperactivity resolved. High-amplitude propagating sequences were absent in early postoperative recordings, and their return temporally correlated with the passage of stool. Abnormal high-amplitude repetitive 0.5 to 1 cycle per minute activity was observed in the left colon of 1 patient with prolonged ileus. LIMITATIONS: The invasive nature of recordings limited this study to a small sample size. CONCLUSIONS: Cyclic motor patterns are markedly hyperactive in the distal colon after right-sided colectomy and resolve during the first 4 postoperative days. High-amplitude propagating sequences are inhibited by surgery and gradually recover. Bowel function may not return until these changes resolve. Other abnormal repetitive hyperactive patterns could contribute to the development of prolonged ileus. See Video Abstract at http://links.lww.com/DCR/B967 . MOTILIDAD HIPERACTIVA DEL COLON DISTAL Y PATRONES DE RECUPERACIN DESPUS DE COLECTOMA DERECHA UN ESTUDIO DE MANOMETRA DE ALTA RESOLUCIN: ANTECEDENTES:El íleo post-operatorio produce una morbilidad significativa, una hospitalización prolongada y un aumento del gasto sanitario. Sin embargo, las anomalías subyacentes en la motilidad siguen siendo poco conocidas. Estudios recientes de manometría de alta resolución demostraron que el colon distal se vuelve hiperactivo con un patrón motor cíclico en el post-operatorio, pero no registraron esta actividad más allá de las 16 horas posteriores a la cirugía.OBJETIVO:Utilizar la manometría de alta resolución para evaluar la motilidad del colon distal durante los primeros cuatro días después de la colectomía del lado derecho.DISEÑO:Estudio observacional de pacientes sometidos a manometría colónica perioperatoria de alta resolución mediante catéter de 36 sensores con 1 cm de resolución.AJUSTE:Un solo hospital terciario.PACIENTES:Pacientes adultos sometidos a resección laparoscópica o abierta de colon del lado derecho de forma electiva.PRINCIPALES MEDIDAS DE RESULTADO:AAparición de patrones motores del colon distal durante el período perioperatorio, definidos según un sistema de clasificación publicado. Los marcadores clínicos de recuperación intestinal incluyeron, tiempo hasta la primera evacuación, dieta oral e íleo posoperatorio prolongado.RESULTADOS:Siete pacientes fueron sometidos a registros de manometría perioperatoria. Los patrones motores cíclicos hiperactivos emergieron intraoperatoriamente y alcanzaron su punto máximo en las primeras 12 horas post-operatorias, ocupando 81,8 ± 3,9% del registro. Esto volvió gradualmente a la normalidad durante los primeros cuatro días, alcanzando el 19,0 ± 4,4% (p = 0,002). Ningún paciente tuvo una evacuación intestinal antes de que se resolviera esta hiperactividad. Las secuencias de propagación de alta amplitud estaban ausentes en las grabaciones post-operatorias tempranas y su retorno se correlacionó temporalmente con el paso de las heces. Se observó actividad anormal de alta amplitud repetitiva de 0,5-1 ciclo / minuto en el colon izquierdo de un paciente con íleo prolongado.LIMITACIONES:La naturaleza invasiva de las grabaciones limitó este estudio a un tamaño de muestra pequeño.CONCLUSIONES:Los patrones motores cíclicos son marcadamente hiperactivos en el colon distal después de la colectomía del lado derecho y se resuelven gradualmente durante los primeros cuatro días posoperatorios. Las secuencias de propagación de gran amplitud se inhiben mediante cirugía y se recuperan gradualmente. Es posible que la función intestinal no regrese hasta que estos cambios se resuelvan. Otros patrones hiperactivos repetitivos anormales podrían contribuir al desarrollo de íleo prolongado. Consulte Video Resumen en http://links.lww.com/DCR/B967 . (Traducción-Dr. Mauricio Santamaria ).

Effect of prucalopride to improve time to gut function recovery following elective colorectal surgery: randomized clinical trial.

BACKGROUND: Delayed return to gut function and prolonged postoperative ileus (PPOI) delay recovery after colorectal surgery. Prucalopride is a selective serotonin-4-receptor agonist that may improve gut motility. METHODS: This was a multicentre, double-blind, parallel, placebo-controlled randomized trial of 2 mg prucalopride versus placebo in patients undergoing elective colorectal resection. Patients with inflammatory bowel disease and planned ileostomy formation were excluded, but colostomy formation was allowed. The study medication was given 2 h before surgery and daily for up to 6 days after operation. The aim was to determine whether prucalopride improved return of gut function and reduced the incidence of PPOI. The primary endpoint was time to passage of stool and tolerance of diet (GI-2). Participants were allocated in a 1 : 1 ratio, in blocks of 10. Randomization was computer-generated. All study personnel, medical staff, and patients were blinded. RESULTS: This study was completed between October 2017 and May 2020 at two tertiary hospitals in New Zealand. A total of 148 patients were randomized, 74 per arm. Demographic data were similar in the two groups. There was no difference in median time to GI-2 between prucalopride and placebo groups: 3.5 (i.q.r. 2-5) versus 4 (3-5) days respectively (P = 0.124). Prucalopride improved the median time to passage of stool (3 versus 4 days; P = 0.027) but not time to tolerance of diet (2 versus 2 days; P = 0.669) or median duration of hospital stay (4 versus 4 days; P = 0.929). In patients who underwent laparoscopic surgery (125, 84.5 per cent), prucalopride improved median time to GI-2: 3 (2-4) days versus 4 (3-5) days for placebo (P = 0.012). The rate of PPOI, complications, and adverse events was similar in the two groups. CONCLUSION: Prucalopride did not improve time to overall recovery of gut function after elective colorectal surgery. Registration number: NCT02947269 (http://www.clinicaltrials.gov).

Wearable devices to monitor recovery after abdominal surgery: scoping review.

BACKGROUND: Wearable devices have been proposed as a novel method for monitoring patients after surgery to track recovery, identify complications early, and improve surgical safety. Previous studies have used a heterogeneous range of devices, methods, and analyses. This review aimed to examine current methods and wearable devices used for monitoring after abdominal surgery and identify knowledge gaps requiring further investigation. METHODS: A scoping review was conducted given the heterogeneous nature of the evidence. MEDLINE, EMBASE, and Scopus databases were systematically searched. Studies of wearable devices for monitoring of adult patients within 30 days after abdominal surgery were eligible for inclusion. RESULTS: A total of 78 articles from 65 study cohorts, with 5153 patients were included. Thirty-one different wearable devices were used to measure vital signs, physiological measurements, or physical activity. The duration of postoperative wearable device use ranged from 15 h to 3 months after surgery. Studies mostly focused on physical activity metrics (71.8 per cent). Continuous vital sign measurement and physical activity tracking both showed promise for detecting postoperative complications earlier than usual care, but conclusions were limited by poor device precision, adherence, occurrence of false alarms, data transmission problems, and retrospective data analysis. Devices were generally well accepted by patients, with high levels of acceptance, comfort, and safety. CONCLUSION: Wearable technology has not yet realized its potential to improve postoperative monitoring. Further work is needed to overcome technical limitations, improve precision, and reduce false alarms. Prospective assessment of efficacy, using an intention-to-treat approach should be the focus of further studies.

The Longitudinal Course of Low-anterior Resection Syndrome: An individual Patient Meta-analysis.

OBJECTIVE: We aimed to better understand the longitudinal course of low anterior resection syndrome (LARS) to guide patient expectations and identify those at risk of persisting dysfunction. SUMMARY BACKGROUND DATA: LARS describes disordered bowel function after rectal resection that significantly impacts quality of life. METHODS: MEDLINE, EMBASE, CENTRAL, and CINAHL databases were systematically searched for studies that enrolled adults undergoing anterior resection for rectal cancer and used the LARS score to assess bowel function at ≥2 postoperative time points. Regression analyses were performed on deidentified patient-level data to identify predictors of change in LARS score from baseline (3-6months) to 12-months and 18-24 months. RESULTS: Eight studies with a total of 701 eligible patients were included. The mean LARS score improved over time, from 29.4 (95% confidence interval 28.6-30.1) at baseline to 16.6 at 36 months (95% confidence interval 14.2%-18.9%). On multivariable analysis, a greater improvement in mean LARS score between baseline and 12 months was associated with no ileostomy formation [mean difference (MD) -1.7 vs 1.7, P < 0.001], and presence of LARS (major vs minor vs no LARS) at baseline (MD -3.8 vs -1.7 vs 5.4, P < 0.001). Greater improvement in mean LARS score between baseline and 18-24 months was associated with partial mesorectal excision vs total mesorectal excision (MD-8.6 vs 1.5, P < 0.001) and presence of LARS (major vs minor vs no LARS) at baseline (MD -8.8 vs -5.3 vs 3.4, P < 0.001). CONCLUSIONS: LARS improves by 18 months postoperatively then remains stable for up to 3 years. Total mesorectal excision, neoadjuvant radiotherapy, and ileostomy formation negatively impact upon bowel function recovery.

Post-operative ileus: definitions, mechanisms and controversies.

Post-operative ileus (POI) is a syndrome of impaired gastrointestinal transit which occurs following abdominal surgery. There are few effective targeted therapies for ileus, and research has been limited by inconsistent definitions and an incomplete understanding of the underlying pathophysiology. Despite considerable effort, there remains no widely-adopted definition of ileus, and recent work has identified variation in outcome reporting is a major source of heterogeneity in clinical trials. Outcomes should be clearly-defined, clinically-relevant, and reflective of the underlying biology, impacts on hospital resources and quality of life. Further collaborative efforts will be needed to develop consensus definitions and a core outcome set for postoperative gastrointestinal recovery. Investigation into the pathophysiology of POI has been hindered by use of low-resolution techniques and difficulties linking cellular mechanisms to dysmotility patterns and clinical symptoms. Recent evidence has suggested the common assumption of post-operative GI paralysis is incorrect, and that the distal colon becomes hyperactive following surgery. The post-operative inflammatory response is important in the pathophysiology of ileus, but the time course of this in humans remains unclear, with the majority of evidence coming from animal models. Future work should investigate dysmotility patterns underlying ileus, and identify biomarkers which may be used to diagnose, monitor and stratify patients with ileus.

Functional Outcome of Laparoscopic-Assisted Resection Versus Open Resection of Rectal Cancer: A Secondary Analysis of the Australasian Laparoscopic Cancer of the Rectum Trial.

BACKGROUND: Low anterior resection syndrome has a significant impact on the quality of life in rectal cancer survivors. Previous studies comparing laparoscopic to open rectal resection have neglected bowel function outcomes. OBJECTIVE: This study aimed to assess whether there is a difference in the functional outcome between patients undergoing laparoscopic versus open resection for rectal adenocarcinoma. DESIGN: Cross-sectional prevalence of low anterior resection syndrome was assessed in a secondary analysis of the multicenter phase 3 randomized clinical trial, Australasian Laparoscopic Cancer of the Rectum Trial (ACTRN12609000663257). SETTING: There were 7 study subsites across New Zealand and Australia. PATIENTS: Participants were adults with rectal cancer who underwent anterior resection and had bowel continuity. MAIN OUTCOME MEASURES: Postoperative bowel function was evaluated using the validated low anterior resection syndrome score and Bowel Function Instrument. RESULTS: The Australasian Laparoscopic Cancer of the Rectum Trial randomized 475 patients with T1-T3 rectal adenocarcinoma less than 15 cm from the anal verge. A total of 257 participants were eligible for, and invited to, participate in additional follow-up; 163 (63%) completed functional follow-up. Overall cross-sectional prevalence of major low anterior resection syndrome was 49% (minor low anterior resection syndrome 27%). There were no differences in median overall Bowel Function Instrument score nor low anterior resection syndrome score between participants undergoing laparoscopic versus open surgery (66 vs 67, p = 0.52; 31 vs 27, p = 0.24) at a median follow-up of 69 months. LIMITATIONS: The major limitations are a result of conducting a secondary analysis; the likelihood of an insufficient sample size to detect a difference in prevalence between the groups and the possibility of selection bias as a subset of the randomized population was analyzed. CONCLUSIONS: Bowel dysfunction affects a majority of rectal cancer patients for a significant time after the operation. In this secondary analysis of a randomized trial, surgical approach does not appear to influence the likelihood or severity of low anterior resection syndrome. See Video Abstract at http://links.lww.com/DCR/B794. RESULTADO FUNCIONAL DE LA RESECCIN ASISTIDA POR LAPAROSCOPIA VERSUS RESECCIN ABIERTA EN CNCER DE RECTO ANLISIS SECUNDARIO DEL ESTUDIO DE CNCER DE RECTO LAPAROSCPICO DE AUSTRALASIA: ANTECEDENTES:El síndrome de resección anterior baja tiene un impacto significativo en la calidad de vida de los supervivientes de cáncer de recto. Los estudios anteriores que compararon la resección rectal laparoscópica con la abierta no han presentado resultados de la función intestinal.OBJETIVO:Evaluar si existe una diferencia en el resultado funcional entre los pacientes sometidos a resección laparoscópica versus resección abierta por adenocarcinoma de recto.DISEÑO:La prevalencia transversal del síndrome de resección anterior baja se evaluó en un análisis secundario del ensayo clínico aleatorizado multicéntrico de fase 3, Estudio Sobre el Cáncer de Recto Laparoscópico de Australasia (Australasian Laparoscopic Cancer of the Rectum Trial, ACTRN12609000663257).AJUSTE:Siete subsitios de estudio en Nueva Zelanda y Australia.PACIENTES:Los participantes eran adultos con cáncer de recto que se sometieron a resección anterior con anastomosis.PRINCIPALES MEDIDAS DE RESULTADO:La función intestinal posoperatoria se evaluó utilizando el previamente validado puntaje LARS y el Instrumento de Función Intestinal.RESULTADOS:El Estudio Sobre el Cáncer de Recto Laparoscópico de Australasia asignó al azar a 475 pacientes con adenocarcinoma rectal T1-T3 a menos de 15 cm del borde anal. 257 participantes fueron elegibles e invitados a participar en un seguimiento adicional. 163 (63%) completaron el seguimiento funcional. La prevalencia transversal general de LARS mayor fue del 49% (LARS menor 27%). No hubo diferencias en la puntuación media general del Instrumento de Función Intestinal ni en la puntuación LARS entre los participantes sometidos a cirugía laparoscópica versus cirugía abierta (66 frente a 67, p = 0,52; 31 frente a 27, p = 0,24) en una mediana de seguimiento de 69 meses.LIMITACIONES:Las principales limitaciones son el resultado de realizar un análisis secundario; se analizó la probabilidad de un tamaño de muestra insuficiente para detectar una diferencia en la prevalencia entre los grupos y la posibilidad de sesgo de selección como un subconjunto de la población aleatorizada.CONCLUSIONES:La disfunción intestinal afecta a la mayoría de los pacientes con cáncer de recto durante un tiempo significativo después de la operación. En este análisis secundario de un ensayo aleatorizado, el abordaje quirúrgico no parece influir en la probabilidad o gravedad del síndrome de resección anterior baja. Consulte Video Resumen en http://links.lww.com/DCR/B794. (Traducción-Dr. Felipe Bellolio).

Potential causes of the preoperative increase in the rectosigmoid cyclic motor pattern: A high-resolution manometry study.

BACKGROUND: Cyclic motor patterns (CMPs) are the most common motor pattern in the distal colon. This study used high-resolution (HR) colonic manometry to quantify trends in distal colonic motor activity before elective colonic surgery, determine the effect of a preoperative carbohydrate load, and compare this with a meal response in healthy controls. METHODS: Fiber-optic HR colonic manometry (36 sensors, 1 cm intervals) was used to investigate distal colonic motor activity in 10 adult patients prior to elective colonic surgery, 6 of whom consumed a preoperative carbohydrate drink (200 kCal). Data were compared with nine healthy volunteers who underwent HR colonic manometry recordings while fasted and following a 700 kCal meal. The primary outcome was the percentage of recording occupied by CMPs, defined as propagating contractions at 2-4 cycles per minute (cpm). Secondary outcomes included amplitude, speed, and distance of propagating motor patterns. RESULTS: The occurrence of CMPs progressively increased in time periods closer to surgery (p = 0.001). Consumption of a preoperative drink resulted in significantly increased CMP occurrence (p = 0.04) and propagating distance (p = 0.04). There were no changes in amplitude or speed of propagating motor patterns during the preoperative period. The increase in activity following a preoperative drink was of similar magnitude to the colonic meal response observed in healthy controls, despite the lesser caloric nutrient load. CONCLUSION: Distal colonic CMP increased in occurrence prior to surgery, amplified by ingestion of preoperative carbohydrate drinks. We hypothesize that anxiety, which is also known to rise with proximity to surgery, could play a contributing role.

Intraoperative serosal extracellular mapping of the human distal colon: a feasibility study.

BACKGROUND: Cyclic motor patterns (CMP) are the predominant motor pattern in the distal colon, and are important in both health and disease. Their origin, mechanism and relation to bioelectrical slow-waves remain incompletely understood. During abdominal surgery, an increase in the CMP occurs in the distal colon. This study aimed to evaluate the feasibility of detecting propagating slow waves and spike waves in the distal human colon through intraoperative, high-resolution (HR), serosal electrical mapping. METHODS: HR electrical recordings were obtained from the distal colon using validated flexible PCB arrays (6 × 16 electrodes; 4 mm inter-electrode spacing; 2.4 cm2, 0.3 mm diameter) for up to 15 min. Passive unipolar signals were obtained and analysed. RESULTS: Eleven patients (33-71 years; 6 females) undergoing colorectal surgery under general anaesthesia (4 with epidurals) were recruited. After artefact removal and comprehensive manual and automated analytics, events consistent with regular propagating activity between 2 and 6 cpm were not identified in any patient. Intermittent clusters of spike-like activities lasting 10-180 s with frequencies of each cluster ranging between 24 and 42 cpm, and an average amplitude of 0.54 ± 0.37 mV were recorded. CONCLUSIONS: Intraoperative colonic serosal mapping in humans is feasible, but unlike in the stomach and small bowel, revealed no regular propagating electrical activity. Although sporadic, synchronous spike-wave events were identifiable. Alternative techniques are required to characterise the mechanisms underlying the hyperactive CMP observed in the intra- and post-operative period. NEW FINDINGS: The aim of this study was to assess the feasibility of detecting propagating electrical activity that may correlate to the cyclic motor pattern in the distal human colon through intraoperative, high-resolution, serosal electrical mapping. High-resolution electrical mapping of the human colon revealed no regular propagating activity, but does reveal sporadic spike-wave events. These findings indicate that further research into appropriate techniques is required to identify the mechanism of hyperactive cyclic motor pattern observed in the intra- and post-operative period in humans.

Prolonged postoperative ileus following right- versus left-sided colectomy: A systematic review and meta-analysis.

AIM: Prolonged postoperative ileus (PPOI) is a common complication following colonic surgery, and is associated with longer hospital stay, greater risk of complications and substantial cost for patients and hospitals. Some reports have recently suggested that gastrointestinal (GI) recovery varies based on the side of resection (i.e., right-sided vs. left-sided colectomy). This systematic review and meta-analysis aimed to compare GI recovery by resection side. METHODS: The MEDLINE, Embase, Cochrane Library and CENTRAL databases were systematically searched for articles reporting GI recovery outcomes in adults undergoing elective right- versus left-sided colectomy (excluding with ileostomy) of any surgical approach. The primary outcome was PPOI, and secondary outcomes included time to first passage of flatus, stool and tolerance of solid diet, and postoperative complications. Subgroup analyses of laparoscopic procedures and cohorts without inflammatory bowel disease and sensitivity analysis of adjusted multivariate results were also performed. RESULTS: Nine studies were identified, of which seven were included in the meta-analysis, comprising 29 068 colectomies (14 581 right-sided; 14 487 left-sided). PPOI was heterogeneously defined and was significantly more likely following right-sided compared to left-sided colectomy regardless of the surgical approach (OR 1.78, 95% CI 1.32-2.39; P < 0.01; I2  = 51%), as well as on subgroup analyses and adjusted multivariate meta-analysis. Secondary outcomes were reported in only a few small studies; hence meta-analysis did not produce reliable results. CONCLUSION: Based on heterogeneous definitions, consistently higher rates of PPOI were observed following right- versus left-sided colectomy. These differences are currently unexplained and highlight the need for further research into the pathophysiology of ileus.

A novel mechanism for acute colonic pseudo-obstruction revealed by high-resolution manometry: A case report.

BACKGROUND: Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic dysmotility and is associated with considerable morbidity. The pathophysiology of ACPO is considered to be multifactorial but has not been clarified. Although colonic motility is commonly assumed to be hypoactive, there is little direct pathophysiological evidence to support this claim. METHODS: A 56-year-old woman who developed ACPO following spinal surgery underwent 24 h of continuous high-resolution colonic manometry (1 cm resolution over 36 cm) following endoscopic decompression. Manometry data were analyzed and correlated with a three-dimensional colonic model developed from computed tomography (CT) imaging. RESULTS: The distal colon was found to be profoundly hyperactive, showing near-continuous non-propagating motor activity. Dominant frequencies at 2-6 and 8-12 cycles per minute were observed. The activity was often dissociated and out-of-phase across adjacent regions. The mean amplitude of motor activity was higher than that reported from pre- and post-prandial healthy controls. Correlation with CT imaging suggested that these disordered hyperactive motility sequences might act as a functional pseudo-obstruction in the distal colon resulting in secondary proximal dilatation. CONCLUSIONS: This is the first detailed description of motility patterns in ACPO and suggests a novel underlying disease mechanism, warranting further investigation and identification of potential therapeutic targets.

Clinical factors associated with successful embolization of lower gastrointestinal bleeding.

AIM: To develop a model of clinical factors that may predict: (1) technically and clinically successful embolization of a bleeding vessel at digital subtraction angiography (DSA) for lower gastrointestinal bleed (LGIB); (2) a negative DSA in the presence of positive CT-mesenteric angiography (CTMA) for LGIB. METHODS: A retrospective cohort study of all DSAs conducted with intent for embolization for acute LGIB over a 10-year period was undertaken. Pre-procedural and intra-procedural clinical variables were evaluated using uni- and multi-variate analysis. RESULTS: One hundred and twenty-three DSAs were evaluated. Technical success was 81% and clinical success 78% where DSA was positive. Technical success was associated with super-selective approach, contrast extravasation on CT, haemoglobin drop, anatomical source and time from CT to DSA on univariate analysis. On multivariate analysis, time from CT to DSA was significant with a higher success probability within 120 min with different factors being salient depending on degree of delay. Clinical success was only associated with activated partial thromboplastin time (<27.5 s). A negative DSA was associated with anatomical source, haemodynamic stability, platelet count and time from CT to DSA on univariate analysis. The latter three remained so on multivariate analysis. CONCLUSION: A triaging approach to utilizing emergency DSA may be helpful. If prolonged delay between CT and DSA is anticipated, with haemodynamic stability and a near-normal platelet count, the DSA may not be fruitful. Technical success may be more likely if DSA occurs within 120 min. Clinical success may be more likely if activated partial thromboplastin time is within normal range.

Chyme reinfusion nutritional management for enterocutaneous fistula: first international application of a novel pump technique.

AIM: High-output enterocutaneous fistulas (ECFs) are an established cause of intestinal failure. Parenteral nutrition (PN) remains the gold standard for nutritional management but is complex, expensive and associated with significant complications. Chyme reinfusion (CR) has been reported by multiple centres as a viable option for nutritional management that improves nutritional status, provides the capacity to cease PN and is cost-effective. The aim of this paper is to describe the first use of a novel pump device (The Insides System™) by an independent centre in Australia for the nutritional management of a patient with high-output ECF. METHOD: CR was performed on a 66-year-old woman with a high-output ECF. The device consists of two main components: a centrifugal pump that sits inside the stoma appliance and a battery-powered driver that is magnetically coupled externally onto the pump. The device allows for bolus CR at a rate of infusion that is manually controlled by the patient based on comfort, volume and effluent viscosity. RESULTS: CR provided adequate nutritional support, with successful cessation of PN. Effective use of the device was learnt easily by the patient with minimal demands on nursing assistance. Side effects of CR (diarrhoea, abdominal cramping) were overcome by the patient's ability to manually adjust the reinfusion rate. CONCLUSION: Our experience with the novel Insides System™ device showed promising results in maintaining nutritional status as well as providing a minimally invasive, easy to use and low-cost system for CR. CR should be considered as a viable alternative for the nutritional management of patients with a high-output ECF.

Altered colonic motility is associated with low anterior resection syndrome.

AIM: Patients frequently suffer from low anterior resection syndrome (LARS) after distal colorectal resection. The pathophysiology of LARS has not been clearly elucidated. We hypothesized that rectosigmoid resection could impair motility patterns in the distal colon, such as the rectosigmoid brake, which contribute to control of stool form and frequency. METHOD: High-resolution colonic manometry was performed in patients who had previously undergone distal colorectal resection (mean 6.8 years after resection) and non-operative controls before and after a standardized meal. Symptoms were assessed using the LARS score. Propagating contractions were compared between patients with and without LARS, and controls. RESULTS: Data were analysed from 23 patients (11 no-LARS; 12 LARS) and nine controls. All groups demonstrated a significant meal response. LARS patients had fewer post-prandial antegrade propagating contractions than controls (P = 0.028), and fewer retrograde propagating contractions both pre- (P = 0.005) and post-prandially (P = 0.004). Post-prandially, the LARS group had a significantly lower percentage of propagating contractions that met the criteria for the cyclic motor pattern compared to the control group (26% vs. 58%; P = 0.009). There were significant differences in antegrade and retrograde amplitude (P = 0.049; P = 0.018) and distance of propagation (P = 0.003; P = 0.002) post-prandially between LARS patients and controls. CONCLUSION: Rectosigmoid resection alters the meal response following anterior resection, including impairment of the rectosigmoid brake cyclic motor pattern. These findings help to quantify the impaired functional motility after rectosigmoid resection and offer new insights into the mechanisms of LARS.

Prospective validation of classification of intraoperative adverse events (ClassIntra): international, multicentre cohort study.

OBJECTIVE: To prospectively assess the construct and criterion validity of ClassIntra version 1.0, a newly developed classification for assessing intraoperative adverse events. DESIGN: International, multicentre cohort study. SETTING: 18 secondary and tertiary centres from 12 countries in Europe, Oceania, and North America. PARTICIPANTS: The cohort study included a representative sample of 2520 patients in hospital having any type of surgery, followed up until discharge. A follow-up to assess mortality at 30 days was performed in 2372 patients (94%). A survey was sent to a representative sample of 163 surgeons and anaesthetists from participating centres. MAIN OUTCOME MEASURES: Intraoperative complications were assessed according to ClassIntra. Postoperative complications were assessed daily until discharge from hospital with the Clavien-Dindo classification. The primary endpoint was construct validity by investigating the risk adjusted association between the most severe intraoperative and postoperative complications, measured in a multivariable hierarchical proportional odds model. For criterion validity, inter-rater reliability was evaluated in a survey of 10 fictitious case scenarios describing intraoperative complications. RESULTS: Of 2520 patients enrolled, 610 (24%) experienced at least one intraoperative adverse event and 838 (33%) at least one postoperative complication. Multivariable analysis showed a gradual increase in risk for a more severe postoperative complication with increasing grade of ClassIntra: ClassIntra grade I versus grade 0, odds ratio 0.99 (95% confidence interval 0.69 to 1.42); grade II versus grade 0, 1.39 (0.97 to 2.00); grade III versus grade 0, 2.62 (1.31 to 5.26); and grade IV versus grade 0, 3.81 (1.19 to 12.2). ClassIntra showed high criterion validity with an intraclass correlation coefficient of 0.76 (95% confidence interval 0.59 to 0.91) in the survey (response rate 83%). CONCLUSIONS: ClassIntra is the first prospectively validated classification for assessing intraoperative adverse events in a standardised way, linking them to postoperative complications with the well established Clavien-Dindo classification. ClassIntra can be incorporated into routine practice in perioperative surgical safety checklists, or used as a monitoring and outcome reporting tool for different surgical disciplines. Future studies should investigate whether the tool is useful to stratify patients to the appropriate postoperative care, to enhance the quality of surgical interventions, and to improve long term outcomes of surgical patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT03009929.