Does the morphology of the umbilicus influence the incidence of surgical site infections in transumbilical single-incision laparoscopic appendectomy?

Background: Transumbilical laparoscopic appendectomy (TULA) may be a feasible alternative to conventional laparoscopic appendectomy. However, a transumbilical incision may increase incisional surgical site infections (SSIs) compared to conventional laparoscopic appendectomy. This study aimed to investigate the relationship between the morphology of the umbilicus and the incidence of SSIs in patients who underwent TULA. Patients and Methods: This retrospective study analysed the medical records of consecutive patients who underwent surgery for acute appendicitis at our institution from June 2016 to October 2020. The patients were assigned to the SSI group (those with an SSI) or the non-SSI group. The morphology of the umbilicus was calculated by measuring its width and depth on preoperative computed tomography images and was compared between the SSI and non-SSI groups. Results: The SSI group included 23 patients, while the non-SSI group included 252 patients. The width of the umbilicus was significantly shorter in the SSI group than in the non-SSI group (29 ± 10 mm vs. 34 ± 9 mm, P = 0.027). The umbilicus was slightly deeper in the SSI group than in the non-SSI group; however, the difference was not significant (16 mm vs. 15 mm, P = 0.384). Conclusions: This was the first study investigating the correlation between the morphology of the umbilicus and SSI development in TULA. SSIs tended to occur more commonly in a narrow and deep umbilicus. An extension of the umbilical incision may help prevent SSI in patients with this umbilical morphology.

Transumbilical Single-Incision Laparoscopic-Assisted Appendectomy (TULAA) Is Useful in Adults and Young Adolescents: Comparison with Multi-Port Laparoscopic Appendectomy.

Background and objectives: Single-port laparoscopic appendectomy (SLA) in most previous studies has used intracorporeal excision of the appendix and needed a longer operative time than multi-port laparoscopic appendectomy (MLA), although SLA does have the potential benefit of an almost invisible scar within the umbilicus. Some studies have reported that extracorporeal transumbilical single-incision laparoscopic-assisted appendectomy (TULAA) in children took a considerably reduced operative time compared to MLA. We adopted TULAA in adults, adding routine dissection of the peritoneal attachment of the appendix. The aim was to compare the operative outcomes between TULAA and MLA. Materials and Methods: Between March 2013 and January 2016, 770 patients with acute uncomplicated and complicated appendicitis from 15 to 75 years of age were enrolled retrospectively. The operation was performed as early (EA) and interval appendectomy (IA). Results: Operative time was shorter in the TULAA group than in the MLA group, except for IA. No open conversion occurred in the TULAA group, except one case of ileocecal resection for IA. No intra-abdominal fluid collection was found in the TULAA group. Extended resection (especially partial cecectomy) was performed less frequently in the TULAA group than in the MLA group for IA. Mean postoperative hospital stay was shorter in the TULAA group for uncomplicated appendicitis. When the data of the EA group and the IA group were compared, operative time was significantly shorter in the IA group for both MLA and TULAA. The open conversion rate and the complication rate tended to be lower in the IA group. Confined to IA, the TULAA group tended to have shorter mean initial, postoperative, and total hospital stays. Conclusions: TULAA can be a useful surgical alternative to MLA in adults and young adolescents, because it lacks open conversion and provides both a shorter operative time and a shorter postoperative hospital stay. TULAA is feasible for IA in that it showed a lower rate of extended resection and complications.

Could laparoscopic appendectomy in pregnant women affect obstetric outcomes? A multicenter study.

PURPOSE: The purpose of this study was to compare the perioperative and obstetric outcomes of pregnant women between laparoscopic surgery and open surgery and to evaluate the predictive factors for overall obstetric outcomes. METHODS: We retrospectively reviewed the medical records of pregnant women who underwent appendectomy between January 2008 and June 2015 at six hospitals affiliated to Hallym University. RESULTS: Eighty patients were evaluated. Twenty-four underwent laparoscopic appendectomy (LA) and 56 underwent open appendectomy (OA). There were no significant differences in the patients' characteristics and gestational age at surgery between the two groups. Operation time, time to flatus, and time to soft food intake were similar in both groups. The length of stay was shorter in the LA group than in the OA group (5.1 vs 8.1 days, P = 0.044). Gestational age at delivery, birth weight, and delivery type were similar in both groups. There was no significant difference in overall obstetric poor outcome (20.8 vs 14.3 %, P = 0.516), including preterm delivery (8.3 vs 7.1 %, P = 1.000) and fetal loss (12.5 vs 7.1 %, P = 0.350). Multivariable analysis revealed that fever >38 °C (P = 0.022) and maternal age (P = 0.044) were independent predictors for the overall poor outcomes. CONCLUSIONS: LA was associated with shorter length of stay compared with OA, but perioperative and obstetric outcomes were similar with both procedures. LA can be safely performed in pregnant women in any trimester.

Comparison of short- and long-term outcomes of an early experience with robotic and laparoscopic-assisted resection for rectal cancer.

BACKGROUND/AIMS: Robotic surgery is increasingly used for rectal cancer. We compared the short- and long-term outcomes between robotic- and laparoscopic-assisted resection for rectal cancer. METHODOLOGY: A retrospective chart review was performed between 2006 and 2010. RESULTS: Seventeen robotic and 61 laparoscopic surgeries were performed consecutively. Median follow-up time was 58.2 months. No operation was converted to open surgery. No difference was observed between the groups for types of operations, diverting ileostomy rate, operation time, blood loss, and postoperative hospital stay, tumor diameter, distal margin, circumferential margin, tumor stage, differentiation, lymphovascular, or perineural invasion. However, the number of harvested lymph nodes was higher in the robot than that in the laparoscopy group (p = 0.017). Overall morbidity and reoperation rates were similar between the groups. The 5-yr overall and disease-free survival rates of all patients were 82.5% and 81.3%, respectively. The 5-yr overall and disease-free survival rates of the robotic and the laparoscopy groups were 94.1% and 79.7% (p = 0.241), and 94.1% and 77.9% (p = 0.159), respectively. CONCLUSIONS: Robot-assisted resection for rectal cancer resulted in harvesting more lymph nodes without increasing morbidity and showed a comparable survival rate, compared with those of laparoscopy.

Short-term surgical outcomes and operative risks of laparoscopic total gastrectomy (LTG) for gastric carcinoma: experience at a large-volume center.

BACKGROUND: Despite the popularity of laparoscopic distal gastrectomy (LDG), laparoscopic total gastrectomy (LTG) remains a challenging procedure because of its technical difficulties and possible complications. In this study, the authors evaluated the short-term surgical outcomes and operative risks of LTG. METHODS: The records of 118 patients who underwent LTG for middle or upper gastric cancer were retrieved from a prospectively constructed database of 1,064 patients who underwent laparoscopic gastrectomy between 2007 and 2011. Surgical outcomes of LTG, such as operative results, postoperative courses, morbidities, and mortality, were investigated and compared with those of LDG patients. RESULTS: Of the 118 LTG patients, one underwent open conversion and three experienced an intraoperative complication. Mean operating time was 292 ± 88 min, and the mean total number of harvested lymph nodes was 41 ± 16. As compared with the LDG group, the LTG group had a significantly longer operation time (292 vs. 220 min, p < 0.001), and significantly more intraoperative blood loss (256 vs. 191 ml, p = 0.002). The overall morbidity rate after LTG was 22.9%, which was significantly higher than after LDG (12.7%, p = 0.002). There were two postoperative mortalities in the LTG group. The most common complications after LTG were anastomosis leakage (n = 9) and luminal bleeding (n = 9), which were followed by anastomosis stricture (n = 4) and abdominal infection (n = 3). Univariate and multivariate analysis revealed that old age [≥60 years, odds ratio (OR) = 2.55, 95% confidence interval (CI) = 0.95-6.84], intraoperative blood loss >200 ml (OR = 3.33, 95% CI = 1.14-9.70), and D2 lymphadenectomy (OR = 3.87, 95% CI = 1.30-11.55) were independent risk factors for postoperative complications after LTG. CONCLUSIONS: LTG is a feasible and acceptable procedure for treatment of middle or upper early gastric cancer. Further refinement of anastomosis techniques and considerable experience of laparoscopic gastrectomy are required for proper application of LTG in gastric carcinoma.

Definition and classification of complications of gastrectomy for gastric cancer based on the accordion severity grading system.

BACKGROUND: Postoperative complications still comprise the marker used most frequently to assess the quality of gastrectomy. However, the definition and grading of morbidity is not standardized, hampering meaningful comparisons over time and among centers. This study proposes specific definitions and a reproducible classification of complications following gastrectomy using standardized grading tools. METHODS: We defined each complication based on the literature, and adopted the Accordion Severity Grading System to stratify morbidity. The classification was applied to 890 patients with gastric cancer seen between January 2010 and April 2011. The correlation between the complication grades and the length of hospital stay (LOS) was analyzed, and risk factors for complications were examined with special reference to severity grade. RESULTS: The overall morbidity rate was 18.1 %. Mild complications occurred in 31 patients (3.5 %), moderate in 77 patients (8.7 %), severe--invasive procedure/no general anesthesia (GA) in 27 patients (3.0 %), severe--invasive procedures/GA in 18 patients (2.0 %), and severe--organ failure in 3 patients (0.3 %). Five patients (0.6 %) died postoperatively. The grade of complications had a significant effect on the LOS (p < 0.001). Operating time and cardiovascular and pulmonary co-morbidities were independent risk factors for severe complications [odds ratio (OR) 1.001, p = 0.016; OR 2.226, p = 0.006; OR = 2.896, p = 0.003, respectively]. CONCLUSIONS: The complications after gastrectomy could be classified into different severity grades that had distinct clinical outcomes. The use of this classification provides more reliable, practical outcome data. Consequently, complications should be reported using a standardized classification tool such as the Accordion Severity Grading System, which requires consensus on the definition of specific complications.

Editorial for the Special Issue on Analysis, Design and Fabrication of Micromixers II.

Micromixers are important components of lab-on-a-chip systems, and also have many biological and chemical applications [...].

Evaluation of Hydrodynamic and Thermal Behaviour of Non-Newtonian-Nanofluid Mixing in a Chaotic Micromixer.

Three-dimensional numerical investigations of a novel passive micromixer were carried out to analyze the hydrodynamic and thermal behaviors of Nano-Non-Newtonian fluids. Mass and heat transfer characteristics of two heated fluids have been investigated to understand the quantitative and qualitative fluid faction distributions with temperature homogenization. The effect of fluid behavior and different Al2O3 nanoparticles concentrations on the pressure drop and thermal mixing performances were studied for different Reynolds number (from 0.1 to 25). The performance improvement simulation was conducted in intervals of various Nanoparticles concentrations (φ = 0 to 5%) with Power-law index (n) using CFD. The proposed micromixer displayed a mixing energy cost of 50-60 comparable to that achieved for a recent micromixer (2021y) in terms of fluid homogenization. The analysis exhibited that for high nanofluid concentrations, having a strong chaotic flow enhances significantly the hydrodynamic and thermal performances for all Reynolds numbers. The visualization of vortex core region of mass fraction and path lines presents that the proposed design exhibits a rapid thermal mixing rate that tends to 0.99%, and a mass fraction mixing rate of more than 0.93% with very low pressure losses, thus the proposed micromixer can be utilized to enhance homogenization in different Nano-Non-Newtonian mechanism with minimum energy.

Kinematic Properties of a Twisted Double Planetary Chaotic Mixer: A Three-Dimensional Numerical Investigation.

In this study, a numerical investigation based on the CFD method is carried out to study the unsteady laminar flow of Newtonian fluid with a high viscosity in a three-dimensional simulation of a twisted double planetary mixer, which is composed of two agitating rods inside a moving tank. The considered stirring protocol is a "Continuous sine squared motion" by using the dynamic mesh model and user-defined functions (UDFs)to define the velocity profiles. The chaotic advection is obtained in our active mixers by the temporal modulation of rotational velocities of the moving walls in order to enhance the mixing of the fluid for a low Reynolds number and a high Peclet number. For this goal, we applied the Poincaré section and Lyapunov exponent as reliable mathematic tools for checking mixing quality by tracking a number of massless particles inside the fluid domain. Additionally, we investigated the development of fluid kinematics proprieties, such as vorticity, helicity, strain rate and elongation rate, at various time periods in order to view the impact of temporal modulation on the flow properties. The results of the mentioned simulation showed that it is possible to obtain a chaotic advection after a relatively short time, which can deeply enhance mixing fluid efficiency.

Evaluation of osteoarthritis induced by treadmill-running exercise using the modified Mankin and the new OARSI assessment system.

To apply the Osteoarthritis Research Society International (OARSI) assessment system to an osteoarthritis model, 44 Wistar rats were randomized into treadmill-running exercise or control group. At 6, 8, and 10 weeks, medial knee joints were histopathologically evaluated, and aggrecan neoepitope and TUNEL staining were performed. Cartilage changes in exercise group were histopathologically and histochemically compatible with early OA. Total modified Mankin system (MMS) scores were significantly higher at all time points (each P ≤ 0.01) in exercise than in control group. However, only tibial OARSI scores of runners were higher at 10 weeks (P < 0.05), although OARSI scores were found to be significantly correlated with MMS scores. Both total MMS (Spearman's coefficient ρ = 0.786) and OARSI scores (ρ = 0.443 for femoral; ρ = 0.604 for tibial) were significantly associated with the exercise duration. In conclusion, the OARSI system may not be sensitive to early OA changes induced by treadmill exercise.

Editorial for the Special Issue on Analysis, Design and Fabrication of Micromixers.

During the last couple of decades, there have been rapid developments in analysis, design, and fabrication of micromixers [...].

Mixing Enhancement of Non-Newtonian Shear-Thinning Fluid for a Kenics Micromixer.

In this work, a numerical investigation was analyzed to exhibit the mixing behaviors of non-Newtonian shear-thinning fluids in Kenics micromixers. The numerical analysis was performed using the computational fluid dynamic (CFD) tool to solve 3D Navier-Stokes equations with the species transport equations. The efficiency of mixing is estimated by the calculation of the mixing index for different cases of Reynolds number. The geometry of micro Kenics collected with a series of six helical elements twisted 180° and arranged alternately to achieve the higher level of chaotic mixing, inside a pipe with a Y-inlet. Under a wide range of Reynolds numbers between 0.1 to 500 and the carboxymethyl cellulose (CMC) solutions with power-law indices among 1 to 0.49, the micro-Kenics proves high mixing Performances at low and high Reynolds number. Moreover the pressure losses of the shear-thinning fluids for different Reynolds numbers was validated and represented.

Kinematic Measurements of Novel Chaotic Micromixers to Enhance Mixing Performances at Low Reynolds Numbers: Comparative Study.

In this work, a comparative investigation of chaotic flow behavior inside multi-layer crossing channels was numerically carried out to select suitable micromixers. New micromixers were proposed and compared with an efficient passive mixer called a Two-Layer Crossing Channel Micromixer (TLCCM), which was investigated recently. The computational evaluation was a concern to the mixing enhancement and kinematic measurements, such as vorticity, deformation, stretching, and folding rates for various low Reynolds number regimes. The 3D continuity, momentum, and species transport equations were solved by a Fluent ANSYS CFD code. For various cases of fluid regimes (0.1 to 25 values of Reynolds number), the new configuration displayed a mixing enhancement of 40%-60% relative to that obtained in the older TLCCM in terms of kinematic measurement, which was studied recently. The results revealed that all proposed micromixers have a strong secondary flow, which significantly enhances the fluid kinematic performances at low Reynolds numbers. The visualization of mass fraction and path-lines presents that the TLCCM configuration is inefficient at low Reynolds numbers, while the new designs exhibit rapid mixing with lower pressure losses. Thus, it can be used to enhance the homogenization in several microfluidic systems.

Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization.

Optimum configuration of a micromixer with two-layer crossing microstructure was performed using mixing analysis, surrogate modeling, along with an optimization algorithm. Mixing performance was used to determine the optimum designs at Reynolds number 40. A surrogate modeling method based on a radial basis neural network (RBNN) was used to approximate the value of the objective function. The optimization study was carried out with three design variables; viz., the ratio of the main channel thickness to the pitch length (H/PI), the ratio of the thickness of the diagonal channel to the pitch length (W/PI), and the ratio of the depth of the channel to the pitch length (d/PI). Through a primary parametric study, the design space was constrained. The design points surrounded by the design constraints were chosen using a well-known technique called Latin hypercube sampling (LHS). The optimal design confirmed a 32.0% enhancement of the mixing index as compared to the reference design.

A Review of Passive Micromixers with a Comparative Analysis.

A wide range of existing passive micromixers are reviewed, and quantitative analyses of ten typical passive micromixers were performed to compare their mixing indices, pressure drops, and mixing costs under the same axial length and flow conditions across a wide Reynolds number range of 0.01-120. The tested micromixers were selected from five types of micromixer designs. The analyses of flow and mixing were performed using continuity, Navier-Stokes and convection-diffusion equations. The results of the comparative analysis were presented for three different Reynolds number ranges: low-Re (Re ≤ 1), intermediate-Re (1 < Re ≤ 40), and high-Re (Re > 40) ranges, where the mixing mechanisms are different. The results show a two-dimensional micromixer of Tesla structure is recommended in the intermediate- and high-Re ranges, while two three-dimensional micromixers with two layers are recommended in the low-Re range due to their excellent mixing performance.

Effects of Bridge-Shaped Microchannel Geometry on the Performance of a Micro Laminar Flow Fuel Cell.

A laminar flow micro fuel cell comprising of bridge-shaped microchannel is investigated to find out the effects of the cross-section shape of the microchannel on the performance. A parametric study is performed by varying the heights and widths of the channel and bridge shape. Nine different microchannel cross-section shapes are evaluated to find effective microchannel cross-sections by combining three bridge shapes with three channel shapes. A three-dimensional fully coupled numerical model is used to calculate the fuel cell's performance. Navier-Stokes, convection and diffusion, and Butler-Volmer equations are implemented using the numerical model. A narrow channel with a wide bridge shape shows the best performance among the tested nine cross-sectional shapes, which is increased by about 78% compared to the square channel with the square bridge shape.

Asymmetrical Split-and-Recombine Micromixer with Baffles.

The present work proposes a planar micromixer design comprising hybrid mixing modules of split-and-recombine units and curved channels with radial baffles. The mixing performance was evaluated numerically by solving the continuity and momentum equations along with the advection-diffusion equation in a Reynolds number range of 0.1-80. The variance of the concentration of the mixed species was considered to quantify the mixing index. The micromixer showed far better mixing performance over whole Reynolds number range than an earlier split-and-recombine micromixer. The mixer achieved mixing indices greater than 90% at Re ≥ 20 and a mixing index of 99.8% at Re = 80. The response of the mixing quality to the change of three geometrical parameters was also studied. A mixing index over 80% was achieved within 63% of the full length at Re = 20.

Single and Multi-Objective Optimization of a Three-Dimensional Unbalanced Split-and-Recombine Micromixer.

The three-dimensional geometry of a micromixer with an asymmetrical split-and-recombine mechanism was optimized to enhance the fluid-mixing capability at a Reynolds number of 20. Single and multi-objective optimizations were carried out by using particle swarm optimization and a genetic algorithm on a modeled surrogate surface. Surrogate modeling was performed using the computational results for the mixing. Mixing and flow analyses were carried out by solving the convection-diffusion equation in combination with the three-dimensional continuity and momentum equations. The optimization was carried out with two design variables related to dimensionless geometric parameters. The mixing effectiveness was chosen as the objective function for the single-objective optimization, and the pressure drop and mixing index at the outlet were chosen for the multi-objective optimization. The sampling points in the design space were determined using a design of experiment technique called Latin hypercube sampling. The surrogates for the objective functions were developed using a Kriging model. The single-objective optimization resulted in 58.9% enhancement of the mixing effectiveness compared to the reference design. The multi-objective optimization provided Pareto-optimal solutions that showed a maximum increase of 48.5% in the mixing index and a maximum decrease of 55.0% in the pressure drop in comparison to the reference design.

Effectiveness of Antithymocyte Globulin Induction Dosing Regimens in Kidney Transplantation Patients: A Network Meta-analysis.

BACKGROUND: Antithymocyte globulin (ATG) is an induction therapy in kidney transplantation, but our knowledge about the relation between outcomes and ATG regimens is limited. We compared ATG effectiveness in kidney transplantation according to dosage and administration schedule. METHODS: Reports from 1970 until May 2018 in CENTRAL, MEDLINE, EMBASE, and Science Citation Index Expanded were searched. We performed direct and indirect network meta-analysis using Bayesian models and generated rankings for ATG dosage and injection number variations by generation mixed treatment comparison.We compared ATG dose and schedule in kidney transplantation in relation to all-cause death, graft failure, antibody-mediated rejection, T-cell mediated rejection, biopsy-proven acute rejection, and bacterial and viral infection. RESULTS: Ten studies (N = 1065) were analyzed by forming 6 groups: ATG alternate doses, 9 mg/kg, 6 mg/kg, and 4.5 mg/kg; single dose, 6 mg/kg, and 4.5 mg/kg; and control. Compared to placebo, ATG regimen variations were not associated with significant differences in survival, viral infection, renal function, or graft survival. ATG regimens 9 and 4.5 mg alternate dosing tended to reduce biopsy-proven acute rejection but without statistical significance. According to the highest rank probability, the 9 mg alternate dosing group had the highest tendency for cytomegalovirus and bacterial infections but without statistical significance. CONCLUSIONS: The rejection frequency tended to be lower for the 9 and 4.5 mg alternate dosing groups. Infections occurred at a higher rate in the 9 mg alternate dosing group, but the differences in the risk of infection among the groups with different ATG regimens were not statistically significant.

Multi-Objective Optimizations of a Serpentine Micromixer with Crossing Channels at Low and High Reynolds Numbers.

In order to maximize the mixing performance of a micromixer with an integrated three-dimensional serpentine and split-and-recombination configuration, multi-objective optimizations were performed at two different Reynolds numbers, 1 and 120, based on numerical simulation. Numerical analyses of fluid flow and mixing in the micromixer were performed using three-dimensional Navier-Stokes equations and convection-diffusion equation. Three dimensionless design variables that were related to the geometry of the micromixer were selected as design variables for optimization. Mixing index at the exit and pressure drop through the micromixer were employed as two objective functions. A parametric study was carried out to explore the effects of the design variables on the objective functions. Latin hypercube sampling method as a design-of-experiment technique has been used to select design points in the design space. Surrogate modeling of the objective functions was performed by using radial basis neural network. Concave Pareto-optimal curves comprising of Pareto-optimal solutions that represents the trade-off between the objective functions were obtained using a multi-objective genetic algorithm at Re = 1 and 120. Through the optimizations, maximum enhancements of 18.8% and 6.0% in mixing index were achieved at Re = 1 and 120, respectively.