Omentum preservation versus complete omentectomy in gastrectomy for gastric cancer (OMEGA trial): study protocol for a randomized controlled trial.

BACKGROUND: Potentially curative therapy for locally advanced gastric cancer consists of gastrectomy, usually in combination with perioperative chemotherapy. An oncological resection includes a radical (R0) gastrectomy and modified D2 lymphadenectomy; generally, a total omentectomy is also performed, to ensure the removal of possible microscopic disease. However, the omentum functions as a regulator of regional immune responses to prevent infections and prevents adhesions which could lead to bowel obstructions. Evidence supporting a survival benefit of routine complete omentectomy during gastrectomy is lacking. METHODS: OMEGA is a randomized controlled, open, parallel, non-inferiority, multicenter trial. Eligible patients are operable (ASA < 4) and have resectable (≦ cT4aN3bM0) primary gastric cancer. Patients will be 1:1 randomized between (sub)total gastrectomy with omentum preservation distal of the gastroepiploic vessels versus complete omentectomy. For a power of 80%, the target sample size is 654 patients. The primary objective is to investigate whether omentum preservation in gastrectomy for cancer is non-inferior to complete omentectomy in terms of 3-year overall survival. Secondary endpoints include intra- and postoperative outcomes, such as blood loss, operative time, hospital stay, readmission rate, quality of life, disease-free survival, and cost-effectiveness. DISCUSSION: The OMEGA trial investigates if omentum preservation during gastrectomy for gastric cancer is non-inferior to complete omentectomy in terms of 3-year overall survival, with non-inferiority being determined based on results from both the intention-to-treat and the per-protocol analyses. The OMEGA trial will elucidate whether routine complete omentectomy could be omitted, potentially reducing overtreatment. TRIAL REGISTRATION: ClinicalTrials.gov NCT05180864. Registered on 6th January 2022.

Effect of omentum preservation on long-term prognosis of locally advanced gastric cancer: a systematic review and meta-analysis.

BACKGROUND: The effect of omentum preservation (OP) on locally advanced gastric cancer (LAGC) remains controversial. This study aimed to investigate the long-term prognosis of LAGC patients with OP versus omentum resection (OR). METHODS: A comprehensive search of databases including PubMed, Web of Science, Embase, and Cochrane Library was conducted up until February 2024. Statistical analysis was performed using Stata 12.0 software. The primary outcome was to assess the impact of OP on the long-term prognosis of patients with LAGC, including overall survival (OS) and recurrence-free survival (RFS). RESULTS: A total of six case-control studies were included, encompassing a cohort of 1897 patients. The OP group consisted of 844 patients, while the OR group comprised 1053 patients. The study results showed that the OS (HR = 0.72, 95% CI: 0.58-0.90, P = 0.003) and 5-year RFS (HR = 0.79, 95% CI: 0.63-0.99, P = 0.038) in the OP group were superior to those observed in the OR group. Subgroup analysis indicated that 5-year OS (HR = 0.64, P = 0.003) and 5-year RFS (HR = 0.69, P = 0.005) in the OP group were also better than those in the OR group in Korea. However, the subgroup analysis conducted on stage T3-T4 tumors revealed no statistically significant differences in OS (P = 0.083) and 5-year RFS (P = 0.173) between the two groups. CONCLUSION: Compared with OR, OP shows non-inferiority in patients with LAGC and can be considered a potential treatment option for radical gastrectomy.

Torsion of a large subserosal fibroid along with omental torsion adherent to it: a rare cause of acute abdomen.

A woman in her 30s presented to emergency with complaints of acute lower abdominal pain for 3 days, not associated with any menstrual, bowel or urinary symptoms. Examination revealed an abdominopelvic mass corresponding to an 18-week gravid uterus with diffuse tenderness and guarding over her lower abdomen. The patient was a follow-up case of subserosal fibroid uterus, chronic kidney disease stage 4 and rheumatic heart disease on anticoagulants. Fibroid degeneration or torsion was suspected. Ultrasound revealed a large posterior wall subserosal fibroid with free fluid in the pelvis. As findings did not suggest degeneration or pedunculated fibroid, noncontrast CT was done, which showed a similar mass with a pedicle arising from the uterine fundus with free fluid with no other evident cause of acute abdomen. The patient was taken up for emergency laparotomy. Intraoperatively, it was found to be a case of subserosal fibroid with greater omentum adhered to it and twisted around its axis about eight times. This case is being reported to highlight a rare cause of acute abdomen.

Cholecystoappendiceal fistula associated with xanthogranulomatous cholecystitis.

Xanthogranulomatous cholecystitis is a rare chronic inflammatory disease of the gallbladder associated with complications such as perforation, dense adhesions and fistulation. We present a case of a female patient in her 20s who presented with three episodes of recurrent cholecystitis over 3 months. Her medical history included an endoscopic retrograde cholangiopancreatography for obstructive jaundice due to choledocholithiasis. As there was no possibility of performing an urgent cholecystectomy during her initial admission, she was listed for an elective operation. Laparoscopic inspection revealed a pericholecystic mass involving the omentum, transverse colon, duodenum and liver and findings suspicious of a cholecystoappendiceal fistula. Laparoscopic cholecystectomy and appendicectomy were performed. Early index admission laparoscopic cholecystectomy should be performed in patients with acute cholecystitis to prevent higher grades of operative difficulty and associated complications. This case presentation-cholecystoappendiceal fistula associated with xanthogranulomatous cholecystitis-emphasises the necessity of complying with national guidelines in managing acute calculous cholecystitis.

Sugar-binding profiles of the mesothelial glycocalyx in frozen tissues of mice revealed by lectin staining.

The mesothelium is a non-adhesive protective surface that lines the serosal cavities and organs within the body. The glycocalyx is a complex structure that coats the outer layer of the mesothelium. However, due to the limitations of conventional fixation techniques, studies on glycans are limited. In this study, lectin staining of frozen tissues was performed to investigate the diversity of glycans in the glycocalyx of mesothelial cells in mice. Datura stramonium lectin (DSL), which recognizes lactosamine and binds to Galectin-3 and -1, was broadly bound to the mesothelial cells of the visceral and parietal peritoneum but not to the pancreas, liver, intestine, or heart. Furthermore, human mesothelial cells in the omentum and parietal peritoneum were positive for DSL. Erythrina cristagalli lectin binding was specific to mesothelial cells in the parietal peritoneum, that is, the pleura, diaphragm, and peritoneum. Intriguingly, surface sialylation, the key element in reducing peritoneal dissemination and implantation, and promoting ascites formation by ovarian carcinoma cells, was much higher in the parietal peritoneum than in the omentum. These findings revealed slight differences in the glycans of mesothelial cells of different organs, which may be related to clinical diseases. These results also suggest that there may be differences in the functions of parietal and visceral mesothelial cells.

Omentoplasty versus cecal mobilization after abdominoperineal resection: A propensity score matching analysis.

BACKGROUND: Despite the minimally invasive approach and early rehabilitation, abdominal-perineal resection (APR) remains a procedure with high morbidity, notably due to postoperative trapped bowel ileus and perineal healing complications. Several surgical techniques have been described for filling the pelvic void to prevent abscess formation and ileus by trapped bowel loop. OBJECTIVE: The aim of our study was to compare the post APR complications for cancer of two of these techniques, omentoplasty and cecal mobilization, in a single-center study from an expert colorectal surgery center. PATIENTS: From 2012 to 2022, 84 patients were included, including 58 (69%) with omentoplasty and 26 (31%) with cecal mobilization. They all underwent APR at Bordeaux University Hospital Center. SETTINGS: A propensity score was used to avoid confounding factors as far as possible. Patient and procedure characteristics were initially comparable. RESULTS: The 30-day complication rate was significantly higher in the cecal mobilization group (53.8% vs. 5.2% p < 0.01), as was the rate of pelvic abscess (34.6% vs. 0% p < 0.001). CONCLUSION: These findings suggest that, when feasible, omentoplasty should be considered the preferred method for pelvic reconstruction following APR.

A Study of Omentum Reduction on the Improvement of Nausea and vomiting and Gastroesophageal Reflux Symptoms After Laparoscopic Gastric Sleeve Resection.

OBJECTIVE: To investigate the effect of omentum reduction in laparoscopic sleeve gastrectomy (LSG) on the improvement of postoperative nausea and vomiting and gastroesophageal reflux symptoms. METHODS: A retrospective study was performed on the case data of 198 obese patients who underwent LSG in the Department of Obesity and Metabolic Diseases of Xiaolan People's Hospital of Zhongshan from March 2021 to March 2022 and were divided into omentum reduction group and control group, with 99 cases in each group, and the preoperative body mass index (BMI) of the patients was recorded. Age, gender, comorbidities, and comparative analysis of operation time, blood loss, length of hospital stay, postoperative nausea and vomiting score, gastroesophageal reflux GerdQ score, postoperative pain score, weight, and postoperative complications were analyzed. RESULTS: There were no significant differences in preoperative BMI, age, gender and comorbidities between the two groups (P > 0.05), but there were significant differences in intraoperative blood loss and operation time (P < 0.05). There were differences in postoperative nausea and vomiting scores and VAS pain scores between the two groups (P < 0.05). The GerdQ scores of the omental reduction group were 8.11 ± 2.84 points at 1 year, and those in the control group were 7.56 ± 2.67 points, which were 3.97 ± 4.09 points higher than those in the preoperative omentum reduction group and 3.42 ± 3.41 in the control group, with no significant difference (P > 0.05). There was no significant difference in the postoperative excess weight loss rate %EWL and postoperative complications (p > 0.05). CONCLUSION: Omentum reduction can improve short-term nausea and vomiting after LSG, but it cannot significantly improve long-term reflux symptoms.

Omentum pregnancy resulting in severe hemoperitoneum: Lessons learned from a review of the literature along with a case report.

Abdominal pregnancies are a rare form of ectopic pregnancy with omentum pregnancies being even rarer. Ectopic pregnancy should be diagnosed and terminated early to prevent the risk of harm to the mother. This case report describes a rare case of omentum pregnancy with severe hemoperitoneum. The patient had not visited a doctor until she failed to menstruate for 3 months, by which point she had developed severe hypogastralgia. The patient was diagnosed with a ruptured ectopic pregnancy after ultrasonography. The omentum pregnancy was complicated by severe hemoperitoneum, which was confirmed by emergency laparotomy. The patient was treated successfully with fetal extraction and partial omentectomy. Ultrasound examination in early pregnancy is essential to detect and treat ectopic pregnancies as early as possible, as surgery is usually required for abdominal pregnancies. Prompt treatment of ectopic pregnancies is critical, as an omentum pregnancy is dangerous and may result in severe intraperitoneal bleeding.

Comparative assessment of the capability of machine learning-based radiomic models for predicting omental metastasis in locally advanced gastric cancer.

The study aims to investigate the predictive capability of machine learning algorithms for omental metastasis in locally advanced gastric cancer (LAGC) and to compare the performance metrics of various machine learning predictive models. A retrospective collection of 478 pathologically confirmed LAGC patients was undertaken, encompassing both clinical features and arterial phase computed tomography images. Radiomic features were extracted using 3D Slicer software. Clinical and radiomic features were further filtered through lasso regression. Selected clinical and radiomic features were used to construct omental metastasis predictive models using support vector machine (SVM), decision tree (DT), random forest (RF), K-nearest neighbors (KNN), and logistic regression (LR). The models' performance metrics included accuracy, area under the curve (AUC) of the receiver operating characteristic curve, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). In the training cohort, the RF predictive model surpassed LR, SVM, DT, and KNN in terms of accuracy, AUC, sensitivity, specificity, PPV, and NPV. Compared to the other four predictive models, the RF model significantly improved PPV. In the test cohort, all five machine learning predictive models exhibited lower PPVs. The DT model demonstrated the most significant variation in performance metrics relative to the other models, with a sensitivity of 0.231 and specificity of 0.990. The LR-based predictive model had the lowest PPV at 0.210, compared to the other four models. In the external validation cohort, the performance metrics of the predictive models were generally consistent with those in the test cohort. The LR-based model for predicting omental metastasis exhibited a lower PPV. Among the machine learning algorithms, the RF predictive model demonstrated higher accuracy and improved PPV relative to LR, SVM, KNN, and DT models.

Microbiota alert: Proteobacteria consume arginine to dampen omental antitumor immunity.

The microbiota can impact antitumor immunity, but whether the microbiota regulates omental antitumor immunity remains elusive. In this issue of Cell Host & Microbe, Meza-Perez et al. demonstrated that Proteobacteria consume arginine to increase Treg cell suppressive capacity and inhibit antitumor immune responses, promoting tumor growth in the omentum.

Cystic lymphangioma of the lesser omentum in an adult patient.

INTRODUCTION: Lymphangiomas belong to the group of benign vascular tumors that originate in the lymphatic tissue. Up to 90% of cases manifest in children before the second year of life. In adults, their presence is very rare. In most cases, they are located in the head, neck and axilla. Intra-abdominal lymphangiomas are very rare and represent less than 1% of all cases. CASE REPORT: The authors present the case of a 64-year-old female patient diagnosed with an intra-abdominal cystic lesion following a routine examination. A CT scan of the abdomen confirmed a cystic lesion located in the lesser omentum between the left lobe of the liver and the lesser curvature of the stomach. The patient was scheduled for laparoscopic exstirpation of the lesion. Histological examination confirmed the clinical diagnosis of cystic lymphangioma of the lesser omentum. CONCLUSION: The etiopathogenesis of lymphangiomas remains unclear. Despite the fact that they are benign tumors, lymphangiomas tend to have an infiltrative pattern of growth, invading surrounding structures. The majority of cases are asymptomatic and the diagnosis is incidental. The gold standard in treatment remains complete surgical extirpation with microscopically negative margins.

[Successful Closure of Postpneumonectomy Bronchopleural Fistula with Inserting Technique of Omental Pedicle Flap into the Right Main Bronchus:Report of a Case].

A 67-year-old male was admitted to our hospital for the treatment of pyothorax due to bronchopleural fistula at right main bronchus after pneumonectomy for lung cancer( squamous cell carcinoma, pathological stageⅢB). After tube drainage and fenestration, we performed operation to close large diameter fistula, that was almost fully opened stump of the right main bronchus. Omental flap was sutured roughly to the fistula with four stiches and inserted into the bronchus lumen, and covered with latissimus dorsi muscle flap to fix omental pedicle flap and additionally performed thoracoplasty to close the residual space of the pleural cavity. Fistula at the stump became airtight after operation and pyothorax was cured, so our method was thought to be available to close large diameter bronchopleural fistula with omental pedicle flap.

Omental metastases in patients with pseudomyxoma peritonei or colorectal peritoneal metastases - is routine omentectomy justified?

BACKGROUND: The greater omentum is routinely resected during cytoreductive surgery (CRS), but few studies have analyzed the rationale behind this. This study aimed to assess the prevalence of omental metastases (OM) and the correlation between macroscopically suspected and microscopically confirmed OM, in patients with pseudomyxoma peritonei (PMP) or colorectal peritoneal metastases (PM). METHOD: All patients without previous omentectomy, treated with initial CRS and hyperthermic intraperitoneal chemotherapy for PMP or colorectal PM, at Uppsala University Hospital in 2013-2021, were included. Macroscopic OM in surgical reports was compared with histopathological analyses. RESULTS: In all, 276 patients were included. In those with PMP, 112 (98%) underwent omentectomy and 67 (59%) had macroscopic suspicion of OM. In 5 (4%) patients, the surgeon was uncertain. Histopathology confirmed OM in 81 (72%). In patients with macroscopic suspicion, 96% had confirmed OM (positive predictive value, PPV). In patients with no suspicion, 24% had occult OM (negative predictive value, NPV = 76%). In patients with colorectal PM, 156 (96%) underwent omentectomy and 97 (60%) had macroscopic suspicion. For 5 (3%) patients, the surgeon was uncertain. OM was microscopically confirmed in 90 (58%). PPV was 85% and NPV was 89%. The presence of OM was a univariate risk factor for death in PMP (HR 3.62, 95%CI 1.08-12.1) and colorectal PM (HR 1.67, 95%CI 1.07-2.60), but not in multivariate analyses. CONCLUSION: OM was common and there was a high risk of missing occult OM in both PMP and colorectal PM. These results support the practice of routine omentectomy during CRS.

Laparoscopically treated bowel obstruction secondary to a lesser omental hernia resulting from a previous laparoscopic total colectomy for ulcerative colitis: A report of two cases.

Lesser omental hernias are rare; however, they should be considered in symptomatic bowel obstruction subsequent to a subtotal or total colectomy. This report describes two cases of recurrent bowel obstruction secondary to lesser omental hernias after laparoscopic total colectomies for ulcerative colitis. Initially, these patients had been treated conservatively; however, due to symptom recurrence, surgical intervention was decided on. In both cases, laparoscopic surgery revealed lesser omental hernias. The small bowel, which had entered from the dorsal aspect of the stomach, was returned to the original position, and the lesser omentum was closed. The patients were discharged uneventfully, with no recurrent bowel obstruction during the follow-up period. These cases highlight the importance of including internal hernias in the differential diagnosis relative to recurrent bowel obstruction, in patient subpopulations with a prior history of a subtotal or total colectomy. Confirmation by computed tomography is preferable.

Efficacy of Omentopexy on Complications of Laparoscopic Sleeve Gastrectomy.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is a commonly performed type of bariatric surgery. Early complications of LSG include bleeding, leakage, pulmonary embolism, and surgical site infections. Most surgeons try to implement preventive methods, such as omentopexy. Staple line-imbrication, which has a difficult learning curve, often prevents complications. This study aimed to evaluate the effect of omentopexy on patients with imbricated LSG. MATERIAL AND METHODS: The study applied a retrospective data analysis design to patients who underwent LSG between 2020 and 2023. All patients' staple lines were imbricated, and patients were then divided into two groups: omentopexy group and control group. Patients' demographic features, such as age, gender, height, weight, body mass index(BMI), bleeding, leakage, and reoperations, were recorded and examined retrospectively. RESULTS: A total of 1356 patients were included in the study (540 in omentopexy, 816 in control), of which the mean age was 37.9 ± 10.5 years, 82.3% were women, and mean BMI was 40.9 ± 5.8 kg/m2. The mean bleeding rate was 1.0% (1.3-0.7%), the mean leakage rate was 0.2% (0.2-0.2%, respectively), and the mean reoperation rate was 0.6% (0.7% and 0.5%, respectively). No statistically significant differences were observed. CONCLUSION: Omentopexy is a technique that is widely used to prevent staple line complications. According to our study, omentopexy applied to an imbricated stapler line increased the operation time but did not affect bleeding or leakage ratios. This is the first study to evaluate the effect of omentopexy on imbricated staple lines. The findings of the study indicate that omentopexy has no additional benefit on early complications when using staple-line imbrication.

Adipocyte pyroptosis occurs in omental tumor microenvironment and is associated with chemoresistance of ovarian cancer.

BACKGROUND: Ovarian carcinoma (OC) is a fatal malignancy, with most patients experiencing recurrence and resistance to chemotherapy. In contrast to hematogenous metastasizing tumors, ovarian cancer cells disseminate within the peritoneal cavity, especially the omentum. Previously, we reported omental crown-like structure (CLS) number is associated with poor prognosis of advanced-stage OC. CLS that have pathologic features of a dead or dying adipocyte was surrounded by several macrophages is well known a histologic hallmark for inflammatory adipose tissue. In this study, we attempted to clarify the interaction between metastatic ovarian cancer cells and omental CLS, and to formulate a therapeutic strategy for advanced-stage ovarian cancer. METHODS: A three-cell (including OC cells, adipocytes and macrophages) coculture model was established to mimic the omental tumor microenvironment (TME) of ovarian cancer. Caspase-1 activity, ATP and free fatty acids (FFA) levels were detected by commercial kits. An adipocyte organoid model was established to assess macrophages migration and infiltration. In vitro and in vivo experiments were performed for functional assays and therapeutic effect evaluations. Clinical OC tissue samples were collected for immunochemistry stain and statistics analysis. RESULTS: In three-cell coculture model, OC cells-derived IL-6 and IL-8 could induce the occurrence of pyroptosis in omental adipocytes. The pyroptotic adipocytes release ATP to increase macrophage infiltration, release FFA into TME, uptake by OC cells to increase chemoresistance. From OC tumor samples study, we demonstrated patients with high gasdermin D (GSDMD) expression in omental adipocytes is highly correlated with chemoresistance and poor outcome in advanced-stage OC. In animal model, by pyroptosis inhibitor, DSF, effectively retarded tumor growth and prolonged mice survival. CONCLUSIONS: Omental adipocyte pyroptosis may contribute the chemoresistance in advanced stage OC. Omental adipocytes could release FFA and ATP through the GSDMD-mediate pyroptosis to induce chemoresistance and macrophages infiltration resulting the poor prognosis in advanced-stage OC. Inhibition of adipocyte pyroptosis may be a potential therapeutic modality in advanced-stage OC with omentum metastasis.

Proteobacteria impair anti-tumor immunity in the omentum by consuming arginine.

Gut microbiota influence anti-tumor immunity, often by producing immune-modulating metabolites. However, microbes consume a variety of metabolites that may also impact host immune responses. We show that tumors grow unchecked in the omenta of microbe-replete mice due to immunosuppressive Tregs. By contrast, omental tumors in germ-free, neomycin-treated mice or mice colonized with altered Schaedler's flora (ASF) are spontaneously eliminated by CD8+ T cells. These mice lack Proteobacteria capable of arginine catabolism, causing increases in serum arginine that activate the mammalian target of the rapamycin (mTOR) pathway in Tregs to reduce their suppressive capacity. Transfer of the Proteobacteria, Escherichia coli (E. coli), but not a mutant unable to catabolize arginine, to ASF mice reduces arginine levels, restores Treg suppression, and prevents tumor clearance. Supplementary arginine similarly decreases Treg suppressive capacity, increases CD8+ T cell effectiveness, and reduces tumor burden. Thus, microbial consumption of arginine alters anti-tumor immunity, offering potential therapeutic strategies for tumors in visceral adipose tissue.