Enteroscopy: Advances in diagnostic imaging

Ruling in or out a source of gastrointestinal bleeding

BACKGROUND AND AIMS

The search for a source of gastrointestinal bleeding is associated with two distinct approaches of trying to rule in a specific diagnosis or rule out any potential source of bleeding. The study aim was to understand the conceptual differences underlying the two searches.

METHODS

The performance of endoscopy as diagnostic test is analyzed in terms of Bayes' formula.

RESULTS

The performance of gastrointestinal endoscopy to rule in a suspected lesion is mostly influenced by its underlying specificity. Because the specificity of endoscopy is less likely to be affected by procedural exigencies, the demands on pre-procedural prep and general quality can be more relaxed. In contradistinction, the performance of endoscopy to rule out a suspected bleeding site is mostly influenced by its sensitivity, which can easily be compromised by suboptimal procedural conditions.

CONCLUSIONS

Paradoxically, the more urgent, focused, and important search (to rule in a bleeding site), carries less stringent criteria for its execution than the more general and aimless search (to rule out a bleeding site) that frequently ends up just empty handed.

Wireless capsule endoscopy of the small intestine: a review with future directions

PURPOSE OF REVIEW

Here, we review the clinical applications of small bowel capsule endoscopy. Moreover, we provide an outlook on the exceptional future developments of small bowel capsule endoscopy. We discuss clinical algorithms for diagnosis of small bowel diseases. Multiple studies have shown the potential of capsule endoscopy for identification of the bleeding source located in the small bowel and the increased diagnostic yield over radiographic studies. Capsule endoscopy could detect villous atrophy and severe complications in patients with nonresponsive celiac disease. In addition, small bowel capsule endoscopy was proven as a valid tool to diagnose polyps and tumors and Crohn's disease.

SUMMARY

Major current clinical indications of capsule endoscopy in the small bowel include evaluation of obscure gastrointestinal bleeding, diagnosis and surveillance of small bowel polyps and tumors, celiac disease and Crohn's disease. Recent developments have also passed the way for small bowel capsule endoscopy to become a therapeutic instrument.

Second harmonic generation imaging distinguishes both high-grade dysplasia and cancer from normal colonic mucosa

BACKGROUND AND AIM

Second harmonic generation (SHG) is a novel imaging technology that could provide optical biopsy during endoscopy with advantages over current technology. SHG has the unique ability to evaluate the amount of extracellular matrix collagen protein and its alignment.

METHODS

Hematoxylin- and eosin-stained slides from colon biopsies (normal, low-grade dysplasia (LGD), high-grade dysplasia (HGD), and cancer) were examined with SHG imaging. Both signal intensity and collagen fiber alignment were measured. Average intensity per pixel (AIPP) was obtained, and an analyzing polarizer was used to calculate β, an alignment parameter.

RESULTS

The mean AIPP for normal mucosa was 48, LGD was 38, HGD was 42, and malignancy was 123 (p < 0.01). The AIPP ROC curve between malignant versus non-malignant tissue was 0.96 (0.93-0.99). An AIPP value of 60 can differentiate malignancy with 87 % sensitivity and 90 % specificity. The mean β for normal tissue was 0.490, LGD was 0.379, HGD was 0.345, and cancer was 0.453 (p = 0.013), with a normal tissue mean rank of 6.5 compared to 2.5 for HGD (p = 0.029).

CONCLUSIONS

SHG signal intensity can differentiate malignant from non-malignant colonic polyp tissue with high sensitivity and specificity. Anisotropic polarization can discern HGD from normal colonic polyp tissue. SHG can thus distinguish both HGD and malignant lesions in an objective numeric fashion, without contrast agents or interpretation skills. SHG could be incorporated into endoscopy equipment to enhance white light endoscopy.