Abdominal hernia (AH) is one of the most common clinical diseases. A large number of observational studies have found that obesity is an important risk factor for AH. However, the causal relationship between obesity and AH cannot be determined because of the clinical studies on AH induced by obesity are relatively few and only have some small- or medium-scale observational studies. Observational studies have so many confounding factors and reverse causality due to their shortcomings. From an evidence-based medicine perspective, they are not sufficiently convincing. Therefore, there is still a lack of high-quality, evidence-based medical evidence supporting a causal relationship between obesity and AH. A causal relationship between obesity and AH is also almost impossible to confirm by randomized controlled trials (RCTs). Our study based on Mendelian randomization (MR) may provide a higher level of evidence-based medical support for the relationship between obesity and AH. Body mass index (BMI) is the most common measure used for defining obesity. Finally, we employed two-sample Mendelian randomization (TSMR) to explore the causal relationship between BMI and AH.
AH-related single nucleotide polymorphisms (SNPs) data were obtained from the FinnGen Biobank (FB), and BMI-related single nucleotide polymorphisms (SNPs) data were obtained from the UK Biobank (UKB). Genetic loci are used as instrumental variables (IVs), methods such as inverse variance weighted (IVW) were used for two-sample Mendelian randomization analysis, and the odds ratio (OR) value was used to evaluate the causal relationship between BMI and AH.
The results of the horizontal pleiotropy test were calculated by Egger-intercept method: p = 0.34 > 0.05. The Cochran Q test of MR-Egger method and IVW method showed heterogeneity P = 0.03 < 0.05, so the IVW random effect model was used as the gold standard. We found a genetically determined 1-standard deviation (SD) increment of BMI causally increased a 66.0% risk of AH (N = 371 SNPs, OR = 1.66, 95% CI 1.46-1.89, p = 1.55E-14) based on the IVW random effect model which was almost consistent with the results of other seven methods.
Our MR found genetic evidence for BMI and AH. The risk of developing AH increases with the number of BMI. This finding provides further evidence that maintaining a healthy BMI can prevent the development of AH. In addition, clinicians may need to focus on the potential risk of AH on some high-BMI patients.

BACKGROUND: Drain-site hernia (DSH) has an extremely low morbidity and has rarely been reported. Small bowel obstruction is a frequent concurrent condition in most cases of DSH, which commonly occurs at the ≥ 10 mm drain-site. Here we report a rare case of DSH at the lateral 5 mm port site one month postoperatively without visceral incarceration. Simultaneously, a brief review of the literature was conducted focusing on the risk factors, diagnosis, and prevention strategies for DSH.
METHODS: A 76-year-old male patient was admitted to our institution with intermittent abdominal pain and a local abdominal mass which occurred one month after laparoscopic radical resection of rectal cancer one year ago. A computed tomography scan showed an abdominal wall hernia at the 5 mm former drain-site in the left lower quadrant, and that the content consisted of the large omentum. An elective herniorrhaphy was performed by closing the fascial defect and reinforcing the abdominal wall with a synthetic mesh simultaneously. The postoperative period was uneventful. The patient was discharged seven days after the operation without surgery-related complications at the 1-mo follow-up visit.
CONCLUSIONS: Emphasis should be placed on DSH despite the decreased use of intra-abdominal drainage. It is recommended that placement of a surgical drainage tube at the ≥ 10 mm trocar site should be avoided. Moreover, it is advisable to have a comprehensive understanding of the risk factors for DSH and complete closure of the fascial defect at the drainage site for high-risk patients.

The use of synthetic surgical meshes for abdominal hernia repair presents numerous challenges due to insufficient mechanical strength, nonabsorbability, and implant rigidity that leads to complications including chronic inflammatory reactions and adhesions. In this study, a naturally derived, high-strength, flexible, and bioresorbable silk fibroin mesh was developed by knitted textile engineering and biochemical manipulation. The mechanical properties of the mesh were optimized with the trial of different surface coating methods (thermal or chemical treatment) and 12 different knit patterns. Our silk fibroin mesh showed sufficient tensile strength (67.83 N longitudinally and 62.44 N vertically) which afforded the high mechanical strength required for abdominal hernia repair (16 N). Compared to the commonly used commercial nonabsorbable and absorbable synthetic meshes (Prolene mesh and Ultrapro mesh, respectively), the developed silk fibroin mesh showed advantages over other meshes, including lower elongation rate (47.14% longitudinally and 67.15% vertically, p < 0.001), lower stiffness (10-1000 fold lower, p < 0.001), and lower anisotropic behavior (λ = 0.32, p < 0.001). In a rat model of large abdominal hernia repair, our mesh facilitated effective hernia repair with minimal chronic inflammation which gradually decreased from 15 to 60 days postoperation, as well as lower adhesion formation rate and scores compared to control meshes. There was more abundant and organized collagen deposition, together with more pronounced neovascularization in the repaired tissue treated with silk fibroin mesh as compared to that treated with synthetic meshes. Besides, the silk fibroin mesh gradually transferred load-bearing responsibilities to the repaired host tissue as it was bioresorbed after implantation. Its isotropic architecture favored an ease of use during operations. In summary, our findings indicate that the use of knitted silk fibroin mesh provides a safe and effective alternative solution for large abdominal hernia repairs as it overcomes the prevailing limitations associated with synthetic meshes.

Abdominal hernia is a common disease, and the most effective treatment of it is using surgical meshes. However, it was found that due to the mismatch of the mechanical properties between the mesh and the tissues around the hernia, there was still a recurrence rate of more than 33% and a high probability of postoperative discomfort. Currently, because of the complex mechanical environment provided by the abdominal tissues and the lack of quantitative research, it is still difficult to select a mesh with suitable mechanical properties for a hernia with specific position and size. Therefore, the purpose of this study is to use numerical models to evaluate the mechanical behavior of both abdominal wall and meshes after repair, and to determine the most suitable mechanical properties of meshes for specific hernias, including elastic modulus and tensile strength. To realize that purpose, defects with different locations and sizes were considered, including defects of 20 mm and 40 mm in diameter on linea alba (LA20 and LA40) and on rectus abdominis (RA20 and RA40), and laparoscopic repair was simulated. The mechanical properties of the most suitable mesh we determined are as follows: suitable modulus for LA20, LA40, RA20 and RA40 are 1 MPa, 3 MPa, 2 MPa and 4 MPa, respectively; suitable tensile strength for LA20, LA40, RA20 and RA40 are 0.35 MPa, 0.89 MPa, 0.77 MPa and 1.43 MPa, respectively. These data could give a standard of mechanical properties which can be referenced in mesh design and evaluation and provide surgeons with treatment advice for specific patients.