Laparoscopic surgery reduced frequency of postoperative small bowel obstruction, and hospital stay compared with open surgery in a cohort of patients with colorectal cancer: a propensity score matching analysis.

BACKGROUND: Laparoscopic surgery (LS) is reported to reduce postoperative complications and hospital stay compared with open surgery (OP). Because patient selection may have been biased in previous studies, propensity score matching (PSM) analysis was used in this study to test the benefits of LS compared with OP. METHODS: A total of 759 patients with stage I-III colorectal cancer undergoing curative surgery were retrospectively reviewed. To minimize confounding bias between LS and OP groups, a 1:1 PSM analysis was performed based on adjuvant chemotherapy, age, albumin, body mass index, American Society of Anesthesiologists physical status depth of tumor, gender, lymph node dissection, maximum tumor size, obstructive tumor, previous abdominal surgery, pathological stage, tumor differentiation, and tumor location. Statistical analyses including chi-square test, Mann-Whitney U test, univariate analyses and Kaplan-Meier method and log-rank test were performed using the data after PSM to investigate the benefits of LS compared with OP. RESULTS: After PSM analysis, 460 patients remained in the study. The LS group had lower intraoperative blood loss (34 ± 70 vs 237 ± 391, mL; P < 0.001), lower frequency of postoperative small bowel obstruction (SBO) (17/213 vs 30/230; P = 0.045), lower rate of nasogastric tube insertion (7/223 vs 17/213; P = 0.036), and shorter postoperative hospital stay (13 ± 10 vs 25 ± 47, day; P < 0.001) than the OP group. Univariate analyses showed that LS significantly reduced the risk of postoperative SBO (odds ratio [OR] 0.532; 95% confidence interval [CI] 0.285-0.995; P = 0.048) and nasogastric tube insertion (OR 0.393; 95% CI 0.160-0.967; P = 0.042) compared with OP. There were no significant differences in OS and RFS between the groups. CONCLUSIONS: LS reduced intraoperative blood loss, frequency of postoperative SBO, rate of nasogastric tube insertion, and postoperative hospital stay compared with OP.

The preoperative pan-immune-inflammation value is a novel prognostic predictor for with stage I-III colorectal cancer patients undergoing surgery.

PURPOSE: The pan-immune-inflammation value (PIV) is useful for stratifying outcomes in patients with metastatic colorectal cancer. However, it is unclear whether preoperative PIV can predict the surgical outcomes of patients with stage I-III colorectal cancer who receive surgery. METHODS: The records of 758 patients with stage I-III colorectal cancer who received surgical treatment were retrospectively reviewed. The preoperative PIV was calculated as follows: (neutrophil count × platelet count × monocyte count)/lymphocyte count. The cut-off value was determined using a receiver operating characteristic curve for overall survival. RESULTS: The cut-off value of the preoperative PIV was 376. Five hundred sixty-eight patients (74.9%) had low values (≤ 376), and 190 (25.1%) had high values (> 376). Univariate and multivariate analyses revealed that the PIV (> 376/ ≤ 376) (HR 2.485; 95% CI 1.552-3.981, P < 0.001) was significantly associated with overall survival, as well as age (> 60/ ≤ 60, years) (HR 1.988; 95% CI 1.038-3.807, P = 0.038), globulin-to-albumin ratio (> 0.83/ ≤ 0.83) (HR 2.013; 95% CI 1.231-3.290, P = 0.005) and postoperative complication (C-D grade III-V/0-II) (HR 1.991; 95% CI 1.154-3.438, P = 0.013). The Kaplan-Meier method and log-rank test showed significant differences in overall survival between patients with stage I-III disease with high (> 376) and low (≤ 376) PIVs. CONCLUSION: The preoperative PIV is useful for predicting surgical outcomes in patients with stage I-III colorectal cancer.

Impact of Primary Tumor Location on Survival After Curative Resection in Patients with Colon Cancer: A Meta-Analysis of Propensity Score-Matching Studies.

BACKGROUND: Recent retrospective subgroup analyses of patients with unresectable colon cancer (CC) receiving systemic chemotherapy have demonstrated that there is a significant difference in treatment outcome between patients with right-sided CC (RSCC) and those with left-sided CC (LSCC). However, it is impossible to divide patients with CC randomly into RSCC and LSCC groups before surgery. Therefore, the aim of this study is to explore the impact of primary tumor location (PTL) on survival after curative surgery for patients with CC using propensity score-matching (PSM) studies instead of randomization. MATERIALS AND METHODS: We performed a comprehensive electronic search of the literature up to January 2019 to identify studies that had used databases allowing comparison of postoperative survival between patients with RSCC and those with LSCC. To integrate the impact of PTL on 5-year overall survival (OS) after curative surgery, a meta-analysis was performed using random-effects models to calculate the risk ratio (RR) and 95% confidence interval (CI) for the selected PSM studies. RESULTS: Five studies involving a total of 398,687 patients with CC were included in this meta-analysis. Among 205,641 patients with RSCC, 69,091 (33.6%) died during the observation period, whereas among 193,046 patients with LSCC, 63,380 (32.8%) died during the same period. These results revealed that patients with RSCC and those with LSCC had almost the same 5-year OS (RR, 0.98; 95% CI, 0.89-1.07; p = .64; I2 = 97%). CONCLUSION: This meta-analysis has demonstrated that there was no significant difference in 5-year OS between patients with RSCC and those with LSCC after curative resection. IMPLICATIONS FOR PRACTICE: To integrate the impact of primary tumor location (PTL) on 5-year overall survival (OS) after curative surgery, five propensity score-matching (PSM) studies involving a total of 398,687 patients with colon cancer (CC) were included in this meta-analysis. Among 205,641 patients with right-sided CC (RSCC), 69,091 (33.6%) died during the observation period, whereas among 193,046 patients with left-sided CC (LSCC), 63,380 (32.8%) died during the same period. These results revealed that patients with RSCC and those with LSCC had almost the same 5-year OS (risk ratio, 0.98; 95% confidence interval, 0.89-1.07; p = .64; I2 = 97%).

Omentectomy Does Not Affect the Postoperative Outcome of Patients With Locally Advanced Gastric Cancer: A Systematic Review and Meta-Analysis.

OBJECTIVE: To explore the influence of omentectomy on postoperative outcomes in patients with locally advanced gastric cancer (LAGC). BACKGROUND: Although several meta-analyses have investigated the influence of bursectomy on postoperative outcomes in patients with LAGC, no meta-analyses have explored the influence of omentectomy on postoperative outcomes in such patients. METHODS: We performed a comprehensive electronic search of the literature up to December 2020 to identify studies that compared postoperative outcomes between patients with LAGC who did and did not undergo omentectomy. A meta-analysis was performed using random-effects models to calculate the risk ratio (RR) and 95% confidence interval (CI), and heterogeneity was analyzed using I2 statistics. RESULTS: Eight retrospective studies involving a total of 2658 patients with LAGC who underwent surgery were included in this meta-analysis. Among them, 3 propensity score matching (PSM) studies demonstrated that the 5-y recurrence-free survival (RFS) rate was 72.9% (314/431) in patients with LAGC who did not undergo omentectomy, whereas it was 70.3% (303/431) in those who did. The results revealed no significant difference in 5-y RFS between groups (RR, 0.91; 95% CI, 0.74-1.13; P = 0.41; I2 = 0%). Two PSM studies also revealed no significant difference in 5-y overall survival (OS) between groups (RR, 0.77; 95% CI, 0.52-1.13; P = 0.18; I2 = 47%). CONCLUSIONS: The results of these meta-analyses show that omentectomy had no significant influence on 5-y OS, especially 5-y RFS, in patients with LAGC.

Severity of liver fibrosis using shear wave elastography is influenced by hepatic necroinflammation in chronic hepatitis patients, but not in cirrhotic patients.

AIM: Shear wave elastography (SWE) in patients with chronic liver diseases is a noninvasive useful method for the diagnosis of liver fibrosis severity, which can be an alternative to liver biopsy. However, the liver stiffness measurement using SWE can be affected by various factors including hepatic inflammation, extrahepatic cholestasis, heart failure, and underlying liver diseases. The aim of this study is to clarify the correlation between liver stiffness using SWE and hepatic necroinflammation serologically and pathologically. METHODS: A total of 843 patients with chronic liver disease who received liver biopsy were analyzed. Liver stiffness measurement using transient elastography (TE) and virtual touch quantification (VTQ) were carried out on the same day as the liver biopsy. The correlation between SWE and hepatic inflammation was analyzed serologically and pathologically. RESULTS: The liver stiffness values increased significantly with the progression of liver fibrosis and inflammation (overall p < 0.001). In patients with F0-1, F2, and F3, TE and VTQ values of A2 or A3 were significantly higher than those of A0 or A1 (p value, all <0.05), but not in patients with F4. The median alanine aminotransferase (ALT) values increased significantly with the progression of liver inflammation (p < 0.001). Moreover, TE and VTQ in patients with ALT ≥70 IU/L were significantly higher than those in patients with ALT <70 IU/L (p < 0.01), but not in patients with F4. CONCLUSION: Shear wave elastography can be affected by hepatic necroinflammation in F0-F3 fibrosis, but not in F4.

A high preoperative Glasgow prognostic score predicts a high likelihood of conversion from laparoscopic to open surgery in patients with colon cancer.

BACKGROUND: Although the use of laparoscopic resection for colon cancer (LRC) has been increasing, conversion to open surgery sometimes becomes necessary because of intraoperative difficulties. Although the Glasgow prognostic score (GPS) is well known to be a predictor of outcome in patients with various cancers, it is unclear whether the preoperative GPS can predict the need for conversion from laparoscopic to open surgery. OBJECTIVE: To investigate factors predictive of conversion from laparoscopic to open surgery in patients with colon cancer. METHODS: Data from 308 consecutive patients who underwent LRC between January 2006 and March 2017 were retrospectively enrolled. Preoperative clinical factors in patients who had undergone LRC were compared between conversion and non-conversion groups, and multivariate regression analysis was performed to identify preoperative factors that might predict conversion from laparoscopic to open surgery. RESULTS: Among 308 patients who had undergone LRC, conversion to open surgery was necessary in 28 (9.1%). Sixteen of the latter patients (6.8%) had GPS 0 (among a total of 234) and 6 (11.5%) had GPS 1 (among a total of 52). The proportion of patients with GPS 2 who required conversion was 27.2% (6/22), which was significantly higher than for those with GPS 0 or 1. Multivariate analysis demonstrated that GPS 2 (odds ratio [OR] 3.352; 95% confidence interval [CI] 1.049-10.71; p = 0.041) and preoperative ileus (OR 7.405; 95% CI 2.386-22.98; p = 0.001) were independent factors predictive of conversion from laparoscopic to open surgery. CONCLUSIONS: A high preoperative GPS is an independent factor predictive of conversion from laparoscopic to open surgery in patients with colon cancer.

Impact of Tumor Location on Postoperative Outcome of Intraductal Papillary Neoplasm of the Bile Duct.

BACKGROUND: The concept of intraductal papillary neoplasm of the bile duct (IPNB) has been proposed to be the biliary equivalent of intraductal papillary mucinous neoplasm (IPMN) of the pancreas. While the classification of IPMNs is based on their location of duct involvement, such classification has not been fully evaluated for IPNBs. The aim of this study is to investigate the value of IPNB classification based on its location. METHODS: A total of 306 consecutive patients who underwent surgical resection with a diagnosis of bile duct tumor were enrolled. Among these patients, 21 were diagnosed as having IPNB. The IPNBs were classified into two groups as follows: extrahepatic IPNB, which located in the distal or perihilar bile duct, and intrahepatic IPNB, which located more peripherally than the hilar bile duct. The clinicopathological features of the two groups were then compared. RESULTS: Extrahepatic IPNB tended to show more invasive characteristics than intrahepatic IPNB (presence of invasive component: 40.0 vs. 9.1%, p = 0.084). Moreover, patients with extrahepatic IPNB showed significantly poorer relapse-free survival (RFS) than those with intrahepatic IPNB [5-year RFS rate (%): 81.8 vs. 16.2, p = 0.014]. CONCLUSION: Patients with intrahepatic IPNB show more favorable pathological characteristics and postoperative survival outcomes than those with extrahepatic IPNB.

Risk Factors for Stoma Outlet Obstruction after Proctocolectomy for Ulcerative Colitis.

Objectives: Stoma outlet obstruction (SOO) occurs with an incidence of approximately 40% after proctocolectomy for Ulcerative colitis (UC) with diverting ileostomy. This study aimed to identify the risk factors for SOO after proctocolectomy with diverting ileostomy for patients with UC. Methods: We reviewed the data of 68 patients with UC who underwent proctocolectomy and diverting ileostomy between April 2006 and September 2021. These cases were analyzed on the basis of clinicopathological and anatomical factors. SOO was defined as small bowel obstruction displaying symptoms of intestinal obstruction, such as abdominal distention, abdominal pain, insertion of a tube through the stoma. Results: The study included 38 (56%) men and 30 (44%) women with a median age of 42 years (range, 21-80). SOO categorized as at least Clavien-Dindo grade II occurred in 11 (16%) patients. Six patients required earlier stoma closure than scheduled. Compared with patients without SOO, patients with SOO had a significantly higher total steroid dose from the onset of UC to surgery (p = 0.02), a small amount of intraabdominal fat (p = 0.04), and a higher rate of laparoscopic surgery (p < 0.01). Conclusions: A high preoperative steroid dose, a small amount of intraabdominal fat and laparoscopic surgery were identified as risk factors for SOO. Early detection and treatment for SOO are important for patients at risk.

Clinical influence of prophylactic lateral lymph node dissection on oncologic outcomes of patients with mid-low rectal cancer undergoing mesorectal excision: a meta-analysis.

BACKGROUND: Although several recent meta-analyses have investigated the clinical influence of the addition of lateral lymph node dissection (LLND) on oncologic outcomes in patients with mid-low rectal cancer (RC) undergoing mesorectal excision (ME), most studies included in such meta-analyses were retrospectively designed. Therefore, this study aimed to explore the clinical influence of prophylactic LLND on oncologic outcomes in patients with mid-low RC undergoing ME. METHODS: A comprehensive electronic search of the literature up to July 2022 was performed to identify studies that compared oncologic outcomes between patients with mid-low RC undergoing ME who underwent LLND and patients with mid-low RC undergoing ME who did not undergo LLND. A meta-analysis was performed using fixed-effects models and the generic inverse variance method to calculate hazard ratios (HRs) and 95% CIs, and heterogeneity was analyzed using I2 statistics. RESULTS: A total of 6 studies, consisting of 3 randomized and 3 propensity score matching studies, were included in this meta-analysis. The results of the meta-analysis of 2 randomized studies demonstrated no significant effect of prophylactic LLND on improving oncologic outcomes concerning overall survival (OS) (HR, 1.22; 95% CI, 0.89-1.69; I2 = 0%; P = .22) and relapse-free survival (RFS) (HR, 1.03; 95% CI, 0.81-1.31; I2 = 28%; P = .83). CONCLUSION: The results of this meta-analysis revealed no significant influence of prophylactic LLND on oncologic outcomes-OS and RFS-in patients with mid-low RC who underwent ME.

Influence of the no-touch isolation technique on oncologic outcomes for patients with colon cancer undergoing curative surgery: A systematic review and meta-analysis.

OBJECTIVE: To explore the influence of the no-touch isolation technique (NTIT) on oncologic outcomes for patients with colon cancer (CC) undergoing curative surgery. BACKGROUND: Although several studies have investigated this topic, there have been no meta-analyses exploring the influence of NTIT on oncologic outcomes for these patients. METHODS: We performed a comprehensive electronic literature search of studies published prior to March 2022 to identify those that compared oncologic outcomes for patients with CC who did or did not undergo NTIT. We conducted a meta-analysis using a random-effects model to calculate risk ratio (RRs) and 95% confidence intervals (CIs), analyzing heterogeneity using I2 statistics. RESULTS: Four studies involving a total of 2885 patients with CC who underwent curative surgery met the inclusion criteria for this meta-analysis. The 5-year overall survival (OS) rate was 76.6% for patients with CC who underwent NTIT and 77.2% for those who did not. A meta-analysis of the 3 studies that reported 5-year OS revealed no significant difference between groups (RR, 0.84; 95% CI, 0.62-1.16; P = 0.30; I2 = 70%). In addition, there were no significant differences in 5-year recurrence-free survival (RR, 1.17; 95% CI, 0.93-1.48; P = 0.19; I2 = 45%), and 5-year liver recurrence-free survival (RR, 0.95; 95% CI 0.62, 1.46; P = 0.82; I2 = 65%). CONCLUSIONS: The use of NTIT has no significant influence on oncologic outcomes for patients with CC undergoing curative surgery.

Total Steroid Intake is Associated With Hospital Mortality in Patients With Pan-Peritonitis due to Colorectal Perforation.

BACKGROUND: Patients with pan-peritonitis (PP) due to colorectal perforation have high mortality rate because colorectal perforation causes septic shock. The association between total steroid intake (TSI) and hospital mortality of such patients is not clear. METHODS: One hundred forty-two patients who underwent surgery for PP due to colorectal perforation were reviewed. Patients were divided into two groups by 8000 mg of TSI. The cut-off value of TSI was determined using a receiver operating characteristic curve for hospital mortality. RESULTS: The cut-off value of TSI for hospital mortality was 8000 mg. Patients with TSI>8000 mg had high rate of hemodialysis, hospital mortality, and elevated neutrophil ratio (>95%) compared with those with TSI≤8000 mg. Multivariate analyses revealed that TSI (>8000/≤8000, mg) (OR, 9.669; 95% CI, 1.011-92.49; P = .049) was significantly associated with hospital mortality as well as bleeding volume (>1000/≤1000, mL) (OR, 26.08; 95% CI, 3.566-190.4; P = .001), lymphocyte ratio (≤4/>4, %) (OR, 7.988; 95% CI, 1.498-42.58; P = .015) and C-reactive protein (≤7.5/>7.5, mg/dL) (OR, 41.66; 95% CI, 4.784-33.33; P = .001). DISCUSSION: There was a significant association between TSI and hospital mortality in patients with PP due to colorectal perforation as well as intraoperative bleeding and systemic inflammatory markers.

N2 Lymph Node Metastasis Is a Useful Predictor of Recurrence in Patients With Stage III Rectal Cancer Undergoing Adjuvant Chemotherapy Using Tegafur-uracil/leucovorin.

BACKGROUND/AIM: Fluoropyrimidine therapy or oxaliplatin combination therapy is recommended for patients with stage III colorectal cancer as adjuvant chemotherapy (AC). However, the criterion for selecting these regimens is still unclear in patients with stage III rectal cancer (RC). In order to select an appropriate regimen of AC for such patients, it is needed to identify characteristics associated with tumor recurrence. PATIENTS AND METHODS: The records of 45 patients with stage III RC undergoing AC using tegafur-uracil/leucovorin (UFT/LV) were retrospectively reviewed. The cut-off value of characteristics was determined using a receiver operating characteristic curve for recurrence. Univariate analyses using Cox-Hazard model for predicting recurrence were performed with clinical characteristics. Survival analysis was performed using Kaplan-Meier method and log-rank test. RESULTS: Thirty patients (66.7%) completed AC using UFT/LV. Fifteen patients (33.3%) did not complete AC because of adverse events, tumor recurrence and others. Sixteen patients (35.6%) had recurrence. Univariate analyses revealed that lymph node metastasis (N2/N1) (p=0.002) was associated with tumor recurrence. Survival analysis showed that lymph node metastasis (N2/N1) could stratify recurrence-free survival (p<0.001). CONCLUSION: N2 lymph node metastasis can predict tumor recurrence in patients with stage III RC undergoing AC using UFT/LV.

Transmission electron microscopy study on the effects of the ultrasound contrast agent Levovist on hepatic cells.

PURPOSE: The Ultrasound Equipment and Safety Committee of The Japan Society of Ultrasonics in Medicine performed experiments to confirm whether contrast-enhanced ultrasonography damages liver cells. METHODS: Rats were injected with 0.1 ml of 300 mg/ml ultrasound contrast agent (UCA). Diagnostic ultrasound pulses with a center frequency of 6 MHz and a mechanical index of 1.9 were applied to rat livers with a water bag as a coupler to maintain a distance of 2-6 cm between the ultrasound probe surface and the liver. Contrast-enhanced ultrasonography was carried out for 10 s to visualize the entire liver. Then, specimens of liver tissue were fixed using two types of fixation: immersion and perfusion fixation. RESULTS: Although some variations were found in electron micrographs of liver tissue fixed using immersion fixation, none of three blinded readers found any significant differences between micrographs of liver tissue from rats receiving UCA with sonication and those from sham-treated control rats. Changes observed were not thought to be group-specific but instead due to differences between individual rats. When the livers were fixed using perfusion fixation and the hepatic vein was cut after injection of physiological saline for perfusion, a large number of vacuoles ≥2 µm in diameter were observed. This finding suggested that hepatic cell damage observed in this study was caused by high perfusion pressure during the liver fixation process rather than by sonication with UCA. CONCLUSION: Blinded readings of electron micrographs showed no clear evidence that the use of Levovist in ADI mode ultrasonography causes significant damage to liver tissue.

Shear wave speed measurement bias in a viscoelastic phantom across six ultrasound elastography systems: a comparative study with transient elastography and magnetic resonance elastography.

PURPOSE: To quantify the bias of shear wave speed (SWS) measurements in a viscoelastic phantom across six different ultrasound (US) systems and to compare the SWS with those from transient elastography (TE) and magnetic resonance elastography (MRE). METHODS: A viscoelastic phantom of stiffness representing fibrotic liver or healthy thyroid was measured with nine (linear probe) and 10 (convex probe) modes of six different US-based shear wave elastography (SWE) systems using linear and convex probes. SWS measurements of three regions of interest were repeated thrice at two focal depths, coupling the probe to the phantom using a jig. An MRE system using three motion-encoding gradient frequencies of 60, 90, and 120 Hz and TE were also used to measure the stiffness of the phantom. RESULTS: The SWS from different SWE systems had mean coefficients of variation of 9.0-9.2% and 5.4-5.6% with linear and convex probes, respectively, in viscoelastic phantom measurement. The focal depth was a less significant source of SWS variability than the system. The total average SWS obtained with US-SWE systems was 19.9% higher than that obtained with MRE at 60 Hz, which is commonly used in clinical practice, and 31.5% higher than that obtained with TE using the M probe. CONCLUSIONS: Despite the measurement biases associated with the SWE systems, biases were not necessarily consistent, and they changed with the probes used and depth measured. The SWS of the viscoelastic phantom obtained using different modalities increased according to the shear wave frequency used.

Postoperative Complications Associated With Intra- Versus Extracorporeal Anastomosis for Laparoscopic Right Colectomy.

OBJECTIVE: To compare the postoperative complications of intracorporeal anastomosis (ICA) and extracorporeal anastomosis (ECA) in patients undergoing laparoscopic right colectomy (LRC). BACKGROUND: Although several studies have compared postoperative complications of ICA and ECA after LRC, most were retrospective studies. METHODS: We performed a comprehensive electronic search of the literature to identify studies that compared postoperative complications between ICA and ECA in patients who underwent LRC. We performed meta-analysis using random-effects models to calculate the risk ratio (RR) and 95% confidence interval (CI) of experiencing complications, and we analyzed heterogeneity using I2 statistics. RESULTS: Fifteen studies consist of randomized controlled trials, case-control studies, and propensity score matching studies involving a total of 3219 patients who underwent LRC were included. Among 1377 patients who received ICA, 255 (18.5%) had postoperative complications, whereas among 1652 patients who received ECA, 373 (22.6%) had such complications. The results of the meta-analysis revealed that ICA was associated with a significantly reduced risk of postoperative complications (RR, .73; 95% CI: .57-.95; P = .02; I2 = 57%) compared with ECA. Although there was no significant difference between the 2 groups in risk of anastomotic leakage (RR, .67; 95% CI: .39-1.17; P = .16; I2 = 8%), there was a significant difference between them in risk of surgical site infection (RR, .50; 95% CI: .34-.71; P = .0002; I2 = 0%). CONCLUSIONS: Intracorporeal anastomosis is associated with a reduced risk of postoperative complications compared with ECA in patients undergoing LRC.

A review of physical and engineering factors potentially affecting shear wave elastography.

It has been recognized that tissue stiffness provides useful diagnostic information, as with palpation as a screening for diseases such as cancer. In recent years, shear wave elastography (SWE), a technique for evaluating and imaging tissue elasticity quantitatively and objectively in diagnostic imaging, has been put into practical use, and the amount of clinical knowledge about SWE has increased. In addition, some guidelines and review papers regarding technology and clinical applications have been published, and the status as a diagnostic technology is in the process of being established. However, there are still unclear points about the interpretation of shear wave speed (SWS) and converted elastic modulus in SWE. To clarify these, it is important to investigate the factors that affect the SWS and elastic modulus. Therefore, physical and engineering factors that potentially affect the SWS and elastic modulus are discussed in this review paper, based on the principles of SWE and a literature review. The physical factors include the propagation properties of shear waves, mechanical properties (viscoelasticity, nonlinearity, and anisotropy), and size and shape of target tissues. The engineering factors include the region of interest depth and signal processing. The aim of this review paper is not to provide an answer to the interpretation of SWS. It is to provide information for readers to formulate and verify the hypothesis for the interpretation. Therefore, methods to verify the hypothesis for the interpretation are also reviewed. Finally, studies on the safety of SWE are discussed.

Impact of anastomotic leakage on postoperative survival of patients with colorectal cancer: A meta-analysis using propensity score matching studies.

OBJECTIVE: To explore the influence of anastomotic leakage (AL) on postoperative survival in patients with colorectal cancer (CRC). BACKGROUND: Although several studies have compared the postoperative survival of patients with CRC with and without AL, the background characteristics of the two groups were not aligned in most studies. METHODS: We performed a comprehensive electronic search of the literature up to March 2020 to identify propensity score matching (PSM) studies that compared postoperative survival between CRC patients with and without AL. A meta-analysis was performed using random-effects models to calculate the risk ratio (RR) and 95% confidence interval (CI), and heterogeneity was analyzed using I (Akiyoshi et al., 2011) [2] statistics. RESULTS: Four PSM studies involving a total of 1676 patients with CRC undergoing surgery were included in this meta-analysis. Among 234 patients who had AL, 163 (69.7%) survived at 5 years after surgery, whereas among 1422 patients who did not have AL, 1156 (81.3%) survived at 5 years after surgery. Background characteristics of the two groups were adjusted with PSM in all 4 studies. The result of the meta-analysis revealed a significant difference between the two groups (RR, 1.63; 95% CI, 1.09-2.45; P = 0.02; I2 = 66%) in 5-year overall survival (OS). CONCLUSIONS: The results of this meta-analysis demonstrate a significantly decreased 5-year OS in patients with CRC who had AL compared with patients with CRC who did not have AL.

Appendectomy Does Not Increase the Risk of Future Emergence of Parkinson's Disease: A Meta-analysis.

OBJECTIVE: To explore the impact of appendectomy history on emergence of Parkinson's disease (PD). BACKGROUND: Although there are several studies to investigate the relationship between appendectomy history and emergence of PD, the results are still controversial. METHODS: We performed a comprehensive electronic search of the literature (the Cochrane Library, PubMed, and the Web of Science) up to April 2020 to identify studies that had employed databases allowing comparison of emergence of PD between patients with and those without appendectomy history. To integrate the impact of appendectomy history on emergence of PD, a meta-analysis was performed using random-effects models to calculate the risk ratio (RR) and 95% confidence interval (CI) for the selected studies, and heterogeneity was analyzed using I2 statistics. RESULTS: Four studies involving a total of 6 080 710 patients were included in this meta-analysis. Among 1 470 613 patients with appendectomy history, 1845 (.13%) had emergences of PD during the observation period, whereas among 4 610 097 patients without appendectomy history, 6743 (.15%) had emergences of PD during the observation period. These results revealed that patients with appendectomy history and without appendectomy had almost the same emergence of PD (RR, 1.02; 95% CI, .87-1.20; P = .83; I2 = 87%). CONCLUSION: This meta-analysis has demonstrated that there was no significant difference in emergence of PD between patients with and those without appendectomy history.

Proposal of a parametric imaging method for quantitative diagnosis of liver fibrosis.

PURPOSE: Coming up with a quantitative diagnosis method for liver fibrosis using ultrasound would be highly significant. To permit tissue characterization using the characteristics of the echo signal such as power spectrum, texture parameters, local attenuation, and statistical characteristics, the relation between complicated scatterer structures and the echo signal must be understood. METHODS: In this study, we analyzed the property of the echo amplitude envelope using computer-simulated scatterer models. These models mimicked various liver conditions to evaluate our quantitative parametric imaging methods. Statistical echo characteristics changed with the density of the heterogeneous scatterer buried in a speckle. RESULTS: The new analysis method for a medium in which some tissues are embedded was proposed in consideration of analysis results from computer simulations. In the new method, it is possible to eliminate the influence of a cyst or veins and to detect the existence of fibers more clearly than in previous methods.