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We investigate strategies to mitigate the impact of environmental noise and surface influences in long-term monitoring of subsurface reservoirs using the borehole-deployable Portable Active Seismic Source (B-PASS). Unlike traditional surface seismic sources, the B-PASS system minimizes the impact of surface environmental factors such as temperature fluctuations and groundwater variations. This capability makes it particularly effective for long-term applications, especially CO 2 storage monitoring. Field tests of B-PASS were conducted in a gas field underlain by a shallow, highly attenuating beach sand. This study tested two source configurations: vertical motion and horizontal motion. By stacking the repeatable signals from B-PASS, we achieved effective noise reduction and enhanced the quality of the seismic signal. The source remained deployed in the borehole for 10 days; stability was quantitatively assessed over 7 days comprising approximately 8,000 sweeps., with stacking providing an hourly temporal resolution. The results demonstrated significant signal propagation to the farthest receiver, located approximately 450 m away, even through a highly attenuating layer. Deeper source deployment proved advantageous, enhancing the signal-to-noise (S/N) ratio for P-waves by up to five times compared to a surface source. The field experiments further demonstrated that environmental noise significantly influenced signal propagation, and midnight was identified as the optimal operational period due to less ambient noise. Therefore, by considering the daily temporal variation of the S/N ratio of the field before the long-term monitoring, we can identify the optimal operation time of the monitoring. To determine the optimal number of signal stacks, we developed a method to evaluate how the S/N ratio varies with stacking number and offset (source–receiver distance). Based on these results, the B-PASS demonstrates its potential as a reliable solution for continuous monitoring, even in geologically challenging environments with surface attenuation and noise, by optimizing the daily monitoring schedule and the number of signal stacks.

Background Postoperative complications are not rare in the elderly population after hepatectomy. However, predicting postoperative risk in elderly patients undergoing hepatectomy is not easy. We aimed to develop a new preoperative evaluation method to predict postoperative complications in patients above 65 years of age using biological impedance analysis (BIA). Methods Clinical data of 59 consecutive patients (aged 65 years or older) who underwent hepatectomy at our institution between 2017 and 2020 were retrospectively analyzed. Risk factors for postoperative complications (Clavien-Dindo ≥ III) were evaluated using multivariate regression analysis. Additionally, a new preoperative risk score was developed for predicting postoperative complications. Results Fifteen patients (25.4%) had postoperative complications, with biliary fistula being the most common complication. Abnormal skeletal muscle mass index from BIA and type of surgical procedure were found to be independent risk factors in the multivariate analysis. These two variables and preoperative serum albumin levels were used for developing the risk score. The postoperative complication rate was 0.0% with a risk score of ≤ 1 and 57.1% with a risk score of ≥ 4. The area under the receiver operating characteristic curve of the risk score was 0.810 ( p  = 0.001), which was better than that of other known surgical risk indexes. Conclusion Decreased skeletal muscle and the type of surgical procedure for hepatectomy were independent risk factors for postoperative complications after elective hepatectomy in elderly patients. The new preoperative risk score is simple, easy to perform, and will help in the detection of high-risk elderly patients undergoing elective hepatectomy.

Background Prediction of failure of nonoperative management (NOM) in uncomplicated appendicitis (UA) is difficult. This study aimed to establish a new prediction model for NOM failure in UA. Methods We included 141 adults with UA who received NOM as initial treatment. NOM failure was defined as conversion to operation during hospitalization. Independent predictors of NOM failure were identified using logistic regression analysis. A prediction model was established based on these independent predictors. Receiver operating characteristic (ROC) curve analysis and the Hosmer–Lemeshow test were used to assess the discrimination and calibration of the model, respectively, and risk stratification using the model was performed. Results Among 141 patients, NOM was successful in 120 and unsuccessful in 21. Male sex, maximal diameter of the appendix, and the presence of fecalith were identified as independent predictors of NOM failure for UA. A prediction model with scores ranging from 0 to 3 was established using the three variables (male sex, maximal diameter of the appendix ≥ 15 mm, and the presence of fecalith). The area under the ROC curve for the new prediction model was 0.778, and the model had good calibration ( P  = 0.476). A score of 2 yielded a sensitivity of 71.4% and a specificity of 90.8%. Patients were stratified into low (0–1), moderate (2), and high (3) risk categories, which had NOM rates of 5.2%, 47.1%, and 77.8%, respectively. Conclusions Our prediction model may predict NOM failure in UA with good diagnostic accuracy and help surgeons select appropriate treatments.

Background Laparoscopic hepatectomy has rapidly evolved and has become a viable alternative to open hepatectomy. However, the dissection of liver parenchyma via the laparoscopic caudal approach (parenchymal transection from the caudal to cranial direction under a laparoscopic caudal view) has several limitations. To avoid these limitations in anatomical hepatectomy along the hepatic vein with the caudal approach, it is important to recognize the “tenting sign of the hepatic vein,” which helps to identify the running of the main trunk of the hepatic vein. Technical Presentation In the bifurcation of the hepatic vein, there is a possibility of splitting of the hepatic vein branch or disorientation between the main trunk and branch. Therefore, it is vital that when the branch is pulled, the main trunk of the hepatic vein appears to be toward the direction of the branch. As a result, the main trunk appears in the direction from the original route to the pseudo route. In the caudal approach, this phenomenon is called “tenting sign of the hepatic vein.” Therefore, liver dissection should be performed in the contralateral and cranial sides of the main trunk, with the “tenting sign of the hepatic vein” in mind. This report describes specific cases of the “tenting sign of the hepatic vein.” Conclusion The “tenting sign of the hepatic vein” from the caudal approach is essential knowledge for safe and reliable anatomical laparoscopic hepatectomy and can lead to expansion of indications in the future.

BackgroundAlthough there are various advantages of laparoscopic liver resection (LLR) over open liver resection, some problems have been reported, such as disorientation and lack of control of bleeding during liver parenchymal dissection. In this study, we discuss a strategy to overcome the disorientation experienced during liver parenchymal dissection, especially in anatomical LLR.Technical presentationThis procedure involves hepatic parenchymal dissection from the hepatic vein branch along its trunk to reveal an important landmark in anatomical LLR. Knowing which region of the liver is perfused into each hepatic vein in preoperative 3D simulation allows the tracing of the hepatic vein branch that naturally leads to the hepatic vein trunk. After that, hepatic resection can be easily completed by dissecting the line connected to the other landmarks, the Glisson branch, the root of the hepatic vein, and the liver demarcation line.ConclusionIn conclusion, this surgical procedure that traces the branch of the hepatic vein exposes the trunk, which makes it a very useful tool for limited laparoscopic anatomical hepatectomy.

Surgery is an important pancreatic ductal adenocarcinoma (PDAC) treatment; existing markers are inadequate prognostic indexes. We herein evaluated the utility of the FA score (fibrinogen/albumin ratio) for predicting PDAC postoperative outcomes. We analysed the data of 67 PDAC patients who underwent surgical resection. The relationship between postoperative outcomes and the FA score was investigated. Performance of the FA score was compared to that of other variables and prognostic indexes. No patient with FA ≥130 survived >3 years, whereas all patients who survived longer had FA <130. The FA score was superior to all other indexes for predicting postoperative outcomes. Patients with FA ≥130 vs. <130 had significantly shorter overall and recurrence-free survival. The FA score is useful for predicting PDAC postoperative outcomes. Preoperatively, it may detect patients likely to have poor postoperative prognoses who may benefit from adjuvant or neoadjuvant therapy, thus improving outcomes.

Purpose Distinguishing colorectal from gastroduodenal perforations is clinically important and challenging. We aimed to establish a scoring model based on objective findings (excluding computed tomography findings) for the diagnosis of colorectal perforation and its differentiation from gastroduodenal perforation. Methods Patients diagnosed with colorectal or gastroduodenal perforations between January 2014 and December 2021 were retrospectively studied. Univariate and multivariate analyses were performed to identify independent variables, and a scoring model was developed based on these variables. Results Among 131 eligible patients, 64 (48.9%) were in the colorectal group and 67 (51.1%) were in the gastroduodenal group. White blood cell count, C-reactive protein, and quick Sequential Organ Failure Assessment score were identified as independent clinical variables associated with the diagnosis of colorectal perforation, which differentiated colorectal perforation from gastroduodenal perforation, and were used to develop a new scoring model. The scores ranged from 0 to 5, with an area under the receiver operating characteristic curve of 0.846. The probabilities of colorectal perforation with scores of 0, 1.5, 2, 3, 3.5, and 5 were 3.2, 20, 55.6, 81.8, 73.9, and 82.4%, respectively. Conclusion The new scoring model may help in treatment selection and perioperative management of patients with gastrointestinal perforation.

Background The mortality rate of gangrenous/perforated appendicitis is higher than that of uncomplicated appendicitis. However, non-operative management of such patients is ineffective. This necessitates their careful exam at presentation to identify gangrenous/perforated appendicitis and aid surgical decision-making. Therefore, this study aimed to develop a new scoring model based on objective findings to predict gangrenous/perforated appendicitis in adults. Methods We retrospectively analyzed 151 patients with acute appendicitis who underwent emergency surgery between January 2014 and June 2021. We performed univariate and multivariate analyses to identify independent objective predictors of gangrenous/perforated appendicitis, and a new scoring model was developed based on logistic regression coefficients for independent predictors. Receiver operating characteristic (ROC) curve analysis and the Hosmer–Lemeshow test were performed to assess the discrimination and calibration of the model. Finally, the scores were classified into three categories based on the probability of gangrenous/perforated appendicitis. Results Among the 151 patients, 85 and 66 patients were diagnosed with gangrenous/perforated appendicitis and uncomplicated appendicitis, respectively. Using the multivariate analysis, C-reactive protein level, maximal outer diameter of the appendix, and presence of appendiceal fecalith were identified as independent predictors for developing gangrenous/perforated appendicitis. Our novel scoring model was developed based on three independent predictors and ranged from 0 to 3. The area under the ROC curve was 0.792 (95% confidence interval, 0.721—0.863), and the Hosmer–Lemeshow test showed a good calibration of the novel scoring model ( P  = 0.716). Three risk categories were classified: low, moderate, and high risk with probabilities of 30.9%, 63.8%, and 94.4%, respectively. Conclusions Our scoring model can objectively and reproducibly identify gangrenous/perforated appendicitis with good diagnostic accuracy and help in determining the degree of urgency and in making decisions about appendicitis management.

Background Atherosclerosis is associated with various comorbidities; nonetheless, its effect on the postoperative complications of colorectal surgery in older patients with colorectal cancer (CRC) remains unclear. This study aimed to evaluate the impact of atherosclerosis on the postoperative complications of colorectal surgery in older adults with CRC. Methods Patients aged ≥ 65 years who underwent surgery for CRC between April 2017 and October 2020 were enrolled. To evaluate atherosclerosis, we prospectively calculated the cardio-ankle vascular index (CAVI) measured by the blood pressure/pulse wave test and abdominal aortic calcification (AAC) score from computed tomography. Risk factors for Clavien–Dindo grade ≥ III postoperative complications were evaluated by univariate and logistic regression analyses. Results Overall, 124 patients were included. The mean CAVI value and AAC score were 9.5 ± 1.8 and 7.0 ± 8.0, respectively. Clavien–Dindo grade ≥ III postoperative complications were observed in 14 patients (11.3%). CAVI (odds ratio, 1.522 [95% confidence interval, 1.073–2.160], p  = 0.019), AAC score (1.083 [1.009–1.163], p  = 0.026); and operative time (1.007 [1.003–1.012], p  = 0.001) were identified as risk factors for postoperative complications. Based on the optimal cut-off values of CAVI and AAC score, the probability of postoperative complications was 27.8% in patients with abnormal values for both parameters, which was 17.4 times higher than the 1.6% probability of postoperative complications in patients with normal values. Conclusions Atherosclerosis, particularly that assessed using CAVI and AAC score, could be a significant predictor of postoperative complications of colorectal surgery in older adults with CRC.

The aim of the present study was to investigate risk factors for the development of grade C compared to grade B cases of postoperative pancreatic fistula (POPF). Clinicopathological data from 43 patients who developed grade B or C POPF were retrospectively analyzed. The following types of factors were analyzed: Patient-related, surgery-related, and pancreas-related, including the value of the drain amylase and the detection of gram-negative rod bacteria within the first 7 postoperative days (PODs). Univariate analysis showed that male sex (p=0.0492) and detection of gram-negative rods within the first 7 PODs (p=0.0010) were risk factors for development of grade C POPF. Only detection of gram-negative rods within the first 7 PODs was a significant factor after multivariate analysis (p=0.0027). Sensitive and specific predictive criteria for early detection of grade C POPF should be developed to allow for a management approach appropriately tailored to this condition.