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.

Computed tomography of a canine omental torsion secondary to a chronic abdominal gossypiboma and concurrent incidental broad ligament torsion.

A 5-year-old female spayed Dogue de Bordeaux was referred for concerns of an abdominal mass and peritoneal effusion. Abdominal radiographs identified a mid-ventral abdominal soft tissue opaque mass containing a radiopaque marker consistent with a gossypiboma. Contrast-enhanced abdominal CT identified two whirl signs associated with the abdominal gossypiboma. Exploratory laparotomy confirmed an omental torsion with encapsulated gossypiboma and concurrent incidental torsion of the remnant of the right broad ligament. Based on a literature review, omental torsions are an unreported complication of gossypibomas in canids.

Ruptured primary omental ectopic pregnancy during the first trimester.

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Omental infarction in an overweight child: conservative treatment is a safe approach.

A previously healthy but overweight (body mass index (BMI) of 24.4) adolescent boy presented with fever and significant right-sided abdominal pain. An abdominal ultrasound scan revealed an omental infarction (OI), which was treated conservatively. OI has been described in overweight teenage children with abdominal trauma but can be missed if not considered. A missed diagnosis could result in an unnecessary laparotomy or laparoscopic surgery. Although CT is the gold standard for diagnosis, ultrasonography is an effective approach to identifying OI in children. The benefits of early diagnosis of OI by abdominal ultrasound include a shorter hospital stay and a reduction in unnecessary investigations and surgery.

Computed tomography of suppurative and neoplastic diseases involving the canine omenta and omental bursa.

The greater and lesser omenta are fused peritoneal folds that largely delimit the omental bursa (lesser peritoneal cavity). The omental bursa is a potential space within the abdominal cavity that communicates with the greater peritoneal cavity via the omental (epiploic) foramen: it is subdivided into the omental vestibule, caudal omental recess, and splenic recess. Aims of this retrospective case series study were to describe the frequencies of CT findings of dogs with confirmed inflammatory or neoplastic disease of the omenta, omental bursa, or both. The sample included seven adult, medium-to-large breed dogs. All had fluid in the greater peritoneal cavity and 5/7 (71%) dogs also had fluid in the omental bursa. Primary suppurative inflammatory disease was present in three dogs, each dog had a large abscess with central gas in either the omental vestibule (two dogs) or caudal omental recess (one dog). Both abscesses in the omental vestibule arose from the papillary process of the caudate liver lobe and were surgically removed without complication. Neoplasia was present in four dogs and either arose from omentum (hemangiosarcoma, carcinoma) or infiltrated the omentum from an adjacent organ (splenic leiomyosarcoma, gastric adenocarcinoma). Neoplasms created mass-like tumors, infiltrative tumors, or both and had variable distribution (focal, multifocal, or locally extensive). All dogs with neoplasia were euthanized. CT signs of inflammatory and neoplastic disease overlapped, but the presence of gas might prioritize abscessation. CT signs helped decide feasibility of surgery based on extent of local invasion, especially involvement of structures passing through the porta hepatis.

Peri-gastric appendagitis with lesser omentum hemorrhagic infarction: US, CT, and MRI findings of a rare entity.

Peri-gastric appendagitis followed associated with gastro-hepatic ligament/lesser omentum hemorrhagic infarction has not been well investigated yet. With an accurate radiological diagnosis of peri-gastric appendagitis, even in case of hemorrhagic infarction, the patient can receive supportive measures for the self-limited pain and can forgo surgery, endoscopy, and further invasive testing.

CT and MR imaging of the greater omentum: Pictorial essay.

The greater omentum is a unique anatomical structure that serves a critical function in the containment of inflammatory and infectious processes within the abdominal cavity. It is also a common site of involvement by metastases, as well as the primary location for various pathologic lesions of clinical significance. Its fibroadipose composition, large size, and position in the most anterior aspect of abdomen allow accurate visualization of the greater omentum on CT and MR images. Careful evaluation of the greater omentum can provide important clues to the diagnosis of the underlying abdominal disorder. The aim of this article is to present the normal appearance of the greater omentum, and the wide spectrum of its pathological features as demonstrated on CT and MRI of the abdomen.

Omental infarction mimicking acute appendicitis with negative radiological findings.

A male in his 30s presented to the emergency department with a 1-day history of supra-umbilical pain migrating to the right iliac fossa. On examination, his abdomen was soft but tender with localised guarding in the right iliac fossa and a positive Rovsing's sign. The patient was admitted under a presumptive diagnosis of acute appendicitis. A CT scan and ultrasound scan of the abdomen and pelvis showed no acute intra-abdominal pathology. He stayed in hospital for 2 days for observation without improvement of symptoms. A diagnostic laparoscopy was therefore performed that revealed an infarcted omentum adherent to the abdominal wall and ascending colon causing congestion of the appendix. The infarcted omentum was resected, and the appendix was removed. The CT images were reviewed by multiple consultant radiologists, but no positive findings were appreciated. This case report demonstrates the potential difficulty in diagnosing omental infarction clinically and radiologically.

Inguinal hernia leading to omental torsion: Role of CT in differentiating from other clinical mimics - a case report and literature review.

Omental torsion is a very rare cause of acute abdomen. Clinically, it mimics other common pathologies such as acute appendicitis, acute diverticulitis and acute cholecystitis. It is therefore no surprise, that it was rarely diagnosed pre operatively before the advent and easy availability of modern imaging techniques. CT scan, in particular, can diagnose omental torsion with confidence pre operatively. This can make conservative treatment possible in cases of primary omental torsion and guide regarding the appropriate treatment in cases of secondary torsion. We present a case of a young male patient who presented to Emergency department with symptoms of acute abdomen. Clinical and laboratory findings were non-specific for any specific cause of acute abdomen. CT scan, however, showed omental fat stranding with whirlpool sign representing omental torsion which was seen to be secondary to left inguinal hernia. Patient was operated in emergency and necrotic omentum was resected and hernia repaired. Post-operative recovery was uneventful.

Diagnostic Value of CT Window Technique for Primary Omentum Infarction.

Objective: The diagnostic value of CT window width technique in primary omentum infarction was evaluated by this study. Methods: The abdominal CT data of 32 patients with clinically diagnosed abdominal omentum infarction were retrospectively selected and analyzed. The fixed window position was 50 HU, and the window width was 135 HU, 250 HU (abdomen), 350 HU (mediastinum), and 500 HU, respectively. The detection rate of lesions was analyzed and compared. Results: Window widths of 135 HU, 250 HU (abdomen), 350 HU (mediastinum), and 500 HU have a detection rate of 12.5% (4 cases), 62.5% (20 cases), 100% (32 cases), 100% (32 cases) for abdominal omental lesions, respectively. However, 500 HU showed worse abdominal bowel and parenchymal organs than 350 HU. Conclusion: According to the comprehensive image quality, the ideal window width for diagnosis of primary omentum infarction is 350HU (mediastinal) window width.

Ultrasonographic misdiagnosis of multicystic mesothelioma of the omentum: A case report.

RATIONALE: Multicystic Mesothelioma (MM) is very rare and preoperative diagnosis is difficult. PATIENT CONCERNS: We report a case of a 34-year-old man with solid abdominal cystic echo mass. Physical examination showed that the patient had a flat and soft abdomen without tenderness or rebound pain, no fluid wave tremor, and no obvious abdominal mass was touched. The patient complained of repeated abdominal distention with nausea for 5 days. Sonographic examination suspected pseudomyxoma peritoneum. DIAGNOSIS: Conventional ultrasound examination showed a cystic solid echo mass in the right abdominal cavity of the patient, with uneven internal echo and honeycomb change, and clear boundary with surrounding organs. Color Doppler suggested that the blood flow in the mass was not obvious. Contrast-enhanced computed tomography of the abdomen revealed hypodensity foci in hepatic and renal crypts and right paracolic sulcus. INTERVENTIONS: Laparoscopic resection of the mass was performed, and the postoperative pathological findings were polycystic mesothelioma (greater omentum). OUTCOMES: After mass resection, all laboratory tests and abdominal ultrasound were normal, and abdominal distension and nausea disappeared. LESSONS: Improved ultrasound diagnosis of MM is useful for clinical decision-making.

ARFI elastography of the omentum: feasibility and diagnostic performance in differentiating benign from malignant omental masses.

OBJECTIVE: To evaluate the feasibility and diagnostic performance of acoustic radiation force impulse (ARFI) elastography in different omental masses (OM). DESIGN: This was a retrospective analysis of 106 patients with OM defined as omental thickness ≥1 cm, who underwent abdominal B-mode ultrasound (US) and standardised ARFI examinations of the OM between September 2018 and June 2021 at our university hospital. A cytohistological confirmation was available in 91/106 (85.8%) of all OM, including all 65/65 (100%) malignant OM (mOM) and 26/41 (63.4%) of benign OM (bOM). In 15/41 (36.6%) of bOM; cross-sectional imaging and or US follow-up with a mean duration of 19.8±3.1 months was performed. To examine the mean ARFI velocities (MAV) for potential cut-off values between bOM and mOM a receiver operating characteristic analysis was implemented. RESULTS: The MAV in the mOM group (2.71±1.04 m/s) was significantly higher than that of bOM group (1.27±0.87 m/s) (p<0.001). Using 1.97 m/s as a cut-off yielded a sensitivity and specificity of 76.9% and 85.4%, respectively, in diagnosing mOM (area under the curve=0.851, 95% CI=0.774 to 0.928). CONCLUSION: ARFI elastography is feasible in the omentum and may represent a good non-invasive additional tool in differentiating bOM from mOM.

Primary omental torsion in children: single-center experience of 17 cases.

OBJECTIVE: Primary omental torsion (POT) is a rare condition in children often misdiagnosed because of a lack of clinical manifestations. Here we present insights gained from the treatment of pediatric POT cases at a single center over 8 years and summarize some influencing factors found in diagnosis and treatment, in order to reduce the misdiagnosis of POT in children in the future. METHODS: Demographic and clinical data of 17 children with POT treated in Shanghai Children's Hospital, Shanghai Jiaotong University from June 2012 to December 2020 were reviewed. RESULTS: The mean age of the 17 pediatric patients was 7.65 ± 2.12 years (range: 4-12 years), sixteen were male. The average time from the pain onset to operation was 73.82 ± 47.21 h (range: 21-144 h). In 5 cases, the ultrasound scan revealed a low-intensity inflammatory mass in the abdominal cavity. Only 1 of the 17 patients had normal body mass index, while others were overweight or obese. The mean computed tomography (CT) value of the mass in the lower right abdomen was - 58.74 ± 10.32 HU (range: - 70 to - 46 HU), which is close to that of its own abdominal wall fat [- 46.29 ± 9.45 HU (range: - 62 to - 32 HU)]. The location of the mass was located in front of the right colon in ten cases, except for two cases near the ligamentum teres. Five patients had whirl sign on CT images and 8 patients had pelvic fluid. Five cases were diagnosed as acute appendicitis and 12 were diagnosed as POT, the preoperative diagnosis was correct in 70.59% of cases. All 17 patients were treated with laparoscopic omentectomy. The average duration of hospitalization was 5.53 ± 1.12 days (range: 4-8 days). All cases were followed up. 1 case relapsed 8 months post operation, while the remaining cases had no complications. CONCLUSION: POT is rare in children with acute abdominal pain, which is more common in obese boys. The fatty mass in front of colon and between rectus abdominis sheath in CT image is specific, which is helpful for diagnosis of POT. Laparoscopy is an effective method for the treatment of POT in children.

Omental lipoma in pediatric age group: clinical presentation, image findings and management.

A 2-year-old female patient, admitted in the emergency room, presented diarrhea for 5 days and bloody stools in the last 24 hours. Physical examination revealed no significant findings. Ultrasound was initially performed, showing an elongated, well delimited and solid mass occupying since right hypocondrium until left iliac fossa, displacing adjacent structures. In sequence, magnetic resonance imaging was performed for confirmation of findings suggestive of omentum lipoma. After 1 week, the surgical resection was performed by videolaparoscopic acess. During 2-year follow-up, there was no sign of recurrence.

Omental desmoplastic small round cell tumor with metastasis.

Desmoplastic small round cell tumor (DSRCT) is a very rare diagnosis with about 200 cases reported in literature. DSRCT is a recently described histopathological entity by Gerald and Rosai in 1989. Abdominopelvic cavity especially peritoneum is the most common site. We report a case of a huge omental DSRCT with lymph node metastasis which was initially misdiagnosed as gastrointestinal stromal tumor on radiology. A 26-year-old male presented with complaints of upper abdominal swelling associated with constant dull pain. On examination there was a large 15 × 12 cm intraabdominal mass in the epigastric and umbilical region. Imaging studies were suggestive of neoplastic mesenchymal etiology. Image-guided fine-needle aspiration cytology (FNAC) was suggestive of mesenchymal neoplastic etiology. On laparotomy, there was a huge 20 × 15 cm mass arising from omentum with multiple omental and mesenteric seedlings and mesenteric, peripancreatic and perigastric lymphadenopathy. The patient underwent debulking surgery with uneventful post-operative recovery. Histopathological examination with immunohistochemistry revealed a diagnosis of DSRCT of omentum and small bowel mesentery with lymph node metastasis. Patient then received adjuvant chemotherapy with multiple chemotherapeutic drugs as per P6 protocol and has stable disease at 1 year follow up.

Primary liposarcoma of the omentum: A case report.

RATIONALE: Omental liposarcoma is extremely rare, and only a few reports have been published in the literature. Due to the rarity of the disease, establishing a clear diagnosis and formulating a treatment plan may be challenging for clinicians. PATIENT CONCERNS: The patient was a 51-year-old woman who presented with a protruding mass and pain in the lower abdomen. DIAGNOSIS: Magnetic resonance imaging revealed a tumor measuring 15 cm in diameter in the pelvis. Ovarian cancer was suspected based on pre-operative imaging findings. INTERVENTIONS: An exploratory laparotomy was performed. Intra-operative analysis of the frozen section suggested a benign tumor. OUTCOMES: Postoperative histopathological analysis confirmed the diagnosis of omental liposarcoma. The patient recovered well after surgery. LESSON: This case report helps clinical oncologists to develop a comprehensive understanding of this disease and treat it accordingly.

Solitary Fibrous Tumor of the Great Omentum: A Case Report and Literature Review.

BACKGROUND: We report a case of a 23-year-old man with a solitary fibrous tumor of the great omentum who presented clinically as a case of dull abdominal pain. CASE PRESENTATION: Solitary fibrous tumor normally occurs in the visceral pleura. Extrathoracic solitary fibrous tumor is rare, especially those from the great omentum, with approximately 31 cases reported in the literature. CONCLUSION: After reviewing and summarizing the imaging findings of 31 cases of solitary fibrous tumor of the greater omentum, we considered that the characteristic findings can provide a reliable basis for preoperative diagnosis.

Complete enclosure of gall bladder inside the lesser omentum - a rare anomaly.

Gall bladder is known for many congenital anomalies such as duplication, intrahepatic position, floating position etc. Most of its anomalies can be detected in ultrasound examination and radiography. We report an extremely rare congenital anomaly of gall bladder as observed in a male cadaver during dissection classes. The gall bladder was totally enclosed in the right free margin of the lesser omentum, in front of the usual contents of the right free margin of lesser omentum. The size, shape and blood supply of the gall bladder were normal. Though this anomaly might not cause any functional disturbances, it might result in complications during laparoscopic cholecystectomy.

[Small Bowel Obstruction Due to Internal Hernia Caused by the Vermiform Appendix, Mesentery of the Small Intestines, and Greater Omentum in a Patient with No History of Abdominal Surgery].

Our patient was a 69-year-old man being treated for hyperlipidemia. He was admitted to our hospital with the chief complaint of vomiting and abdominal pain. Abdominal computed tomography(CT)showed dilation of the distal small intestines, a small amount of ascites in the small intestines near the right pelvis, and a closed loop of the small intestine. Enhanced abdominal CT was performed to evaluate intestinal ischemia. Given the adequate blood flow to the wall, the small intestines forming the closed loop, and no increase in ascites, the patient was treated conservatively. Diagnostic laparoscopy was performed because of the narrowed lumen and incomplete obstruction observed on the abdominal CT and contrast- enhanced imaging of the ileal tube. The tip of the appendix adherent to the mesentery of the small intestines, approximately 80 cm from the ileum, and the omentum adherent to the bottom of the right pelvis caused the obstruction. A cord dissection and appendectomy were performed. Making the diagnosis was difficult because there was no history of appendicitis and the small intestinal obstruction was caused by adhesions in 2 places with no history of laparotomy.