Experimental investigations of the human oesophagus: anisotropic properties of the embalmed mucosa-submucosa layer under large deformation.

Mechanical characterisation of the layer-specific, viscoelastic properties of the human oesophagus is crucial in furthering the development of devices emerging in the field, such as robotic endoscopic biopsy devices, as well as in enhancing the realism, and therefore effectiveness, of surgical simulations. In this study, the viscoelastic and stress-softening behaviour of the passive human oesophagus was investigated through ex vivo cyclic mechanical tests. Due to restrictions placed on the laboratory as a result of COVID-19, only oesophagi from cadavers fixed in formalin were allowed for testing. Three oesophagi in total were separated into their two main layers and the mucosa-submucosa layer was investigated. A series of uniaxial tensile tests were conducted in the form of increasing stretch level cyclic tests at two different strain rates: 1% s[Formula: see text] and 10% s[Formula: see text]. Rectangular samples in both the longitudinal and circumferential directions were tested to observe any anisotropy. Histological analysis was also performed through a variety of staining methods. Overall, the longitudinal direction was found to be much stiffer than the circumferential direction. Stress-softening was observed in both directions, as well as permanent set and hysteresis. Strain rate-dependent behaviour was also apparent in the two directions, with an increase in strain rate resulting in an increase in stiffness. This strain rate dependency was more pronounced in the longitudinal direction than the circumferential direction. Finally, the results were discussed in regard to the histological content of the layer, and the behaviour was modelled and validated using a visco-hyperelastic matrix-fibre model.

Transnasal endoscopy: moving from endoscopy to the clinical outpatient-blue sky thinking in oesophageal testing.

Background: COVID-19 has severely affected UK endoscopy services with an estimate 86% loss of activity during the first wave. Subsequent delays in diagnostic and surveillance procedures highlight the need for novel solutions to tackle the resultant backlog. Transnasal endoscopy (TNE) provides an attractive option compared with conventional upper gastrointestinal endoscopy given its limited use of space, no sedation and reduced nursing resources. Our experience: We describe piloting and then establishing an outpatient model TNE service in the pandemic era and the implications on resource allocation, training and workforce. We also discuss our experiences and outline ways in which services can evolve to undertake more complex endoscopic diagnostic and therapeutic work. Over 90% of patients describe no discomfort and those who have previously experienced conventional transoral endoscopy preferred the transnasal approach. We describe a low complication rate (0.8%) comprising two episodes of mild epistaxis. The average procedure duration was reasonable (9.9±5.0 min) with full adherence to Joint Advisory Group quality standards. All biopsies assessed were deemed sufficient for diagnosis including those for surveillance procedures. Discussion: TNE can offer a safe, tolerable, high-quality service outside of a conventional endoscopy setting. Expanding procedural capacity without impacting on the current endoscopy footprint has great potential in recovering endoscopy services following the COVID-19 pandemic. Looking forward, TNE has potential to be used both within the endoscopy suite as part of therapeutic procedures, or outside of the endoscopy unit in outpatient clinics, community hospitals, or mobile units and to achieve this in a more sustainable and environmentally friendly way.

Experimental investigations of the human oesophagus: anisotropic properties of the embalmed muscular layer under large deformation.

The oesophagus is a primarily mechanical organ whose material characterisation would aid in the investigation of its pathophysiology, help in the field of tissue engineering, and improve surgical simulations and the design of medical devices. However, the layer-dependent, anisotropic properties of the organ have not been investigated using human tissue, particularly in regard to its viscoelastic and stress-softening behaviour. Restrictions caused by the COVID-19 pandemic meant that fresh human tissue was not available for dissection. Therefore, in this study, the layer-specific material properties of the human oesophagus were investigated through ex vivo experimentation of the embalmed muscularis propria layer. For this, a series of uniaxial tension cyclic tests with increasing stretch levels were conducted at two different strain rates. The muscular layers from three different cadaveric specimens were tested in both the longitudinal and circumferential directions. The results displayed highly nonlinear and anisotropic behaviour, with both time- and history-dependent stress-softening. The longitudinal direction was found to be stiffer than the circumferential direction at both strain rates. Strain rate-dependent behaviour was apparent, with an increase in strain rate resulting in an increase in stiffness in both directions. Histological analysis was carried out via various staining methods; the results of which were discussed with regard to the experimentally observed stress-stretch response. Finally, the behaviour of the muscularis propria was simulated using a matrix-fibre model able to capture the various mechanical phenomena exhibited, the fibre orientation of which was driven by the histological findings of the study.

Special Issue. (Special Issue.)

This special issue contains five articles which highlight the effects that the coronavirus disease 2019 (COVID-19) can have on the gastrointestinal tract and liver. One article illustrates how COVID-19 can affect pediatric gastrointestinal patients who have additional chronic disorders such as inflammatory bowel disease as well as patients who have undergone a liver transplant. Various disease symptoms and presentation of eosinophilic esophagitis, acute pancreatitis and constipation as well as review of the diagnostic criteria are also covered. Lastly, a review of the intestinal microbiome, including various probiotics and dietary interventions that have changed the way we think about this ever-expanding field.

Tailored endoscopic treatment of tracheo-oesophageal fistula using preoperative holographic assessment and a cardiac septal occluder.

Devices originally designed for closure of cardiac septal defects have also been proposed for the treatment of acquired tracheo-oesophageal fistula (TOF). Choosing the right occluder device to match TOF size and shape is essential for a tailored treatment. We report the successful endoscopic closure of a post-radiotherapy TOF using preprocedural CT scan with holographic three-dimensional reconstruction and an Amplatzer atrial septal device. Complete TOF sealing was achieved with resolution of respiratory symptoms, and the patient was maintaining his ability to eat at 4-month follow-up.

Black oesophagus, upside-down stomach and cameron lesions: cascade effects of a large hiatal hernia.

Acute oesophageal necrosis, black oesophagus (BE) or Gurvits syndrome (GS) is a rare form of severe oesophagitis appearing as a striking circumferential discolouration of distal mucosa with various proximal extensions abruptly terminating at the gastro-oesophageal junction. It is most commonly associated with acute exacerbations of medical comorbidities, while associations with altered gut anatomy are rare. We present a unique constellation of BE, Cameron ulcers (CU), and gastric volvulus from a large paraesophageal hiatal hernia. Our patient recently recovered from COVID-19 and was malnourished and frail, while the expanding paraesophageal hiatal hernia turned into an acute organoaxial gastric volvulus with accompanying outlet obstruction. In low-flow post-COVID coagulopathic states, compensatory mechanisms may lack against gastric stunning and sudden massive reflux on the oesophagus. We additionally performed a systematic review and discovered additional cases with coexistent volvulus and paraesophageal hernia, although there are no previous reports of BE with CU, which makes this study the first.

Acute oesophageal necrosis in a patient with recent SARS-CoV-2.

A 57-year-old Hispanic man with diabetes presented with dyspnoea. He had a positive SARS-CoV-2 PCR. He was intubated for severe hypoxia and treated with intermittent pressors, methylprednisolone and supportive care. He was extubated on hospital day (HD) 9 and discharged to a skilled nursing facility (SNF) on HD 18. Approximately 1 month later, he presented with melena. Endoscopy revealed two large 1.5-2 cm wide-based distal oesophageal ulcers without active bleeding. Histology showed ulcerated squamous mucosa with extensive necrosis extending to the muscularis propria and coccoid bacterial colonies with rare fungal forms suggestive of Candida He was treated with fluconazole and pantoprazole and was discharged to a SNF. Approximately 3 weeks later, he was readmitted for complications. Repeat endoscopy demonstrated improvement and histology revealed chronic inflammation with reactive epithelial changes. Incidentally, SARS-CoV-2 PCR was positive during this visit without any respiratory symptoms.