Introduction
Capsule endoscopy (CE) is a first-line diagnostic tool for known or suspected small bowel
bleeding (SBB), and its use has over time been expanded to include panenteric imaging. It
offers advantages over conventional endoscopy in minimal invasiveness and ease of use.
However several drawbacks remain including the lack of modalities other than imaging,
inability to control or propel the capsule, lesser image quality compared to conventional
endoscopy and labour-intensiveness of data interpretation.
Aims and objectives
This thesis aims to explore the ways in which use of CE can be optimised in the current clinical
or “real world” context, focusing on its use in gastrointestinal bleeding and working within
current resource and technological limitations.
Methods
A review and analysis of the existing literature was undertaken, examining the present state
of CE technology and identifying current gaps in knowledge. Meta-analyses were undertaken
examining the effectiveness of the two main methods of image enhancement in CE: the use
of bowel preparation and currently available rudimentary computer-aided diagnosis.
The following studies then looked into how to better select patients who should be prioritised
for CE examination – a pertinent issue in today’s resource-stretched healthcare systems. A
retrospective study was carried out to examine the effects of altering the timing of CE
examination in patients referred for likely SBB, using cases carried out at our tertiary care
centre over the past decade. Outcomes were compared between patients who had
undergone CE following negative bidirectional endoscopies, or negative upper
gastrointestinal tract endoscopy only. Furthermore, building on existing work, a second study
was undertaken using a prospectively-designed database to collect multicentre data on
findings and outcomes in young patients referred for CE with iron deficiency anaemia. This
study investigated factors predictive of small bowel neoplasia in this patient group.
Finally, the effect of image visualisation quality on diagnostic certainty was investigated. CE
images were processed to alter image parameters, and the resulting images presented to an
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international group of expert CE readers in order to determine thresholds for acceptable
image quality and the effects of differing image quality in the parameters examined.
Results
Currently-available image enhancement techniques:
(1) Use of bowel preparation: Laxative use did not improve the diagnostic yield of CE with
odds ratio (OR) 1.1 for both overall and significant findings when comparing laxative use with
pre-procedural fast only. However, subjectively-determined small bowel visualisation quality
improved with the use of laxatives (OR 1.60 (95%CI 1.08–2.06)), NNT 14.
(2) Use of suspected blood indicator (SBI): The overall sensitivity of SBI for bleeding or
potentially bleeding lesions was 0.553, specificity 0.578, DOR 12.354. The sensitivity of SBI
for active bleeding was 0.988, specificity 0.646, DOR 229.89.
(3) Use of FICE digital image enhancement: Overall, the use of the three FICE modes did not
significantly improve image delineation or detection rate in CE. For pigmented lesions only,
FICE setting 1 performed better in lesion delineation and detection.
Patient selection and CE pathways:
The earlier use of CE in inpatients with melena or IDA, no signs of lower gastrointestinal
pathology and negative UGIE resulted in shortened hospital stays, significant diagnostic yield
from both small bowel and upper gastrointestinal tract, and two-thirds less unnecessary
colon investigations without affecting clinical outcomes.
In young patients (age <50 years) with IDA and negative bidirectional GI endoscopy, the
overall diagnostic yield of CE for clinically significant findings was 32.3%. 5% of our cohort
was diagnosed with SB neoplasia; lower MCV and weight loss were associated with higher
diagnostic yield for significant SB pathology.
Effects of visualisation quality on diagnostic certainty:
Poor visualisation quality in all parameters affected mostly neoplastic lesions. Software to
increase contrast and sharpen images can improve visualisation quality; smart frame rate
adaptation could improve the number of high-quality frames obtained. Thoroughness in
small bowel cleansing was found to be most important when there is suspicion of neoplasia.
Conclusions
The data in this thesis show that CE could be employed earlier in the diagnostic pathway for
patients presenting clinically with SBB, as an effective diagnostic and triage tool in the semi
acute setting. Although the overall diagnostic yield of CE is lower in younger patients, young
patients with IDA and no significant findings on bidirectional endoscopy are also more likely
to have significant small bowel findings, and should perhaps be referred preferentially for CE.
This would help increase the efficiency of resource utilisation.
Of the currently available image enhancement techniques in CE, digital image enhancement
and diagnostic tools such as SBI and FICE remain of limited validity; however they show the
most promise for vascular lesions and active GI bleeding, which supports their use in the
acute to semi-acute setting to improve efficiency of CE reading. Image enhancement with
both laxatives and digital means is the most crucial when patients are suspected of having
more subtle small bowel findings such as small bowel neoplasia
