Background: Advancements in genome editing technology and the globalization of life science research have highlighted the need for refined techniques in individualizing fertilized mouse eggs. Traditional embryo transfer surgery, which demands precise and objective success assessment, presents challenges for technical mastery and animal welfare. To address these issues, we developed a novel culture medium incorporating a dye library that enhances the visibility of ultrafine capillaries. Results: We screened 32 compounds based on their color properties and excluded those with clear cytotoxicity through colony formation inhibition tests. Five compounds demonstrated developmental outcomes comparable to those of the control group during embryo culture. Gene expression analysis revealed high correlation with control embryos, indicating no adverse developmental impact. No maternal toxicity was observed during and after embryo transfer using the dyed medium, which also produced normal offspring. A randomized survey confirmed improved visibility compared to conventional methods. Conclusion This study successfully identified nontoxic dyes that enhance the visibility of embryo transfer culture media, potentially improving precision and animal welfare in embryological research. Based on our findings, adding Brilliant Blue FCF or Fast Green FCF to the medium is recommended.

Background/Aims: Patients with acute cholecystitis (AC) after metallic stent (MS) placement for malignant biliary obstruction (MBO) have a high surgical risk. We performed percutaneous transhepatic gallbladder aspiration (PTGBA) as the first treatment for AC. We aimed to identify the risk factors for AC after MS placement and the poor response factors of PTGBA. Methods: We enrolled 401 patients who underwent MS placement for MBO between April 2011 and March 2020. The incidence of AC was 10.7%. Of these 43 patients, 37 underwent PTGBA as the first treatment. The patients’ responses to PTGBA were divided into good and poor response groups. Results: There were 20 patients in good response group and 17 patients in poor response group. Risk factors for cholecystitis after MS placement included cystic duct obstruction (p<0.001) and covered MS (p<0.001). Cystic duct obstruction (p=0.003) and uncovered MS (p=0.011) demonstrated significantly poor responses to PTGBA. Cystic duct obstruction is a risk factor for cholecystitis and poor response factor for PTGBA, whereas covered MS is a risk factor for cholecystitis and an uncovered MS is a poor response factor of PTGBA for cholecystitis. Conclusions The onset and poor response factors of AC after MS placement were different between covered and uncovered MS. PTGBA can be a viable option for AC after MS placement, especially in patients with covered MS.