Advanced endoscopic techniques and optical diagnosis in the lower gastrointestinal tract

Smith, Samuel Charles Lloyd (2023). Advanced endoscopic techniques and optical diagnosis in the lower gastrointestinal tract. University of Birmingham. Ph.D.

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Abstract

Inflammatory bowel disease describes debilitating chronic diseases (Ulcerative colitis and Crohn’s Disease) of the gastrointestinal tract that requires many patients to take long term medications, have an increased risk of malignancy and can often lead to major abdominal surgery. With the advent of modern therapies, in particular biological therapies, clinicians and patients can increasingly achieve mucosal healing. Mucosal healing is associated with favourable outcomes such as reduced hospitalisation, colectomy and fewer courses of steroids. However, the definition of mucosal healing was based on endoscopic scoring systems developed in a previous generation of endoscopic technology. Novel endoscopic technology, such as Virtual Electronic Chromoendoscopy, can gain more accurate assessments of inflammatory activity, closing the gap to histological activity. The term optical diagnosis refers to the ability of an endoscopist to accurately predict the histology of an endoscopic finding, albeit in predicting inflammatory activity in inflammatory bowel disease or in predicting the histology of a colorectal polyp. With ever improving endoscopic technology successful optical diagnosis is increasingly possible.

The PICaSSO score is a score that was developed using Virtual Electronic Chromoendoscopy and is the first to define endoscopic features in keeping with mucosal healing. This thesis includes a large multicentre international prospective study which investigates the correlation of the PICaSSO score and other established endoscopic scores (MES and UCEIS) against multiple histological indices (RHI, NHI, ECAP, Geboes, and Villanacci) and prospectively assessed outcomes at 6 and 12 months. There was strong correlation between PICaSSO and histology scores, significantly superior to correlation coefficients of MES and UCEIS with histology scores. A PICaSSO score of ≤3 detected histologic remission by RHI with AUROC 0.90 (95% CI 0.86-0.94). PICaSSO score ≤3 predicted better outcomes than PICaSSO >3.

The next study moves from optical characterisation to molecular characterisation of inflammatory activity using Raman Spectroscopy. Raman Spectroscopy (RS) describes the scattering of inelastic light giving spectra that are highly specific for individual molecules. This study aimed to establish spectral changes before and after treatment and whether Raman Spectroscopy can accurately differentiate between inflammation and MH. Reductions in intensity at 1003cm-1 and 1252cm-1 when a reduction in inflammation was seen post-treatment and when MH was present. MH was associated with an increase in intensity at 1304cm-1. A trained neural network differentiated MH from active inflammation with high sensitivity, specificity, PPV, NPV and accuracy in UC and CD. Raman Spectroscopy may represent an additional tool in the assessment of mucosal healing in IBD.

To implement optical diagnosis in practice there needs to be robust training. The next study presents a randomised controlled study comparing the performance of self-training vs. didactic training on the diagnostic accuracy of diminutive/small colonic polyp histological prediction by trainees using established polyp classification tools. The study showed self-learning can achieve results similar to didactic training which, could enable widespread implementation of optical diagnosis in clinical practice. Following this study, I present a meta-analysis and systematic review of optical diagnosis training in small/diminutive colorectal polyps. Optical diagnosis training is effective in improving accuracy of histology prediction in colorectal polyps and didactic and computer-based training show comparable effectiveness in improving diagnostic accuracy. The final study presented is implementing optical diagnosis training and setting quality standards in IBD surveillance endoscopy. A significant improvement in quality was seen in the proportion of procedures using dye-based chromoendoscopy, use of polyp classification tools and an increase lesion detection.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):