Efficacy of high magnification chromoscopic colonoscopy for the diagnosis of neoplasia in flat and depressed lesions of the colorectum: a prospective analysis

Abstract

Background: High magnification chromoscopic colonoscopy (HMCC) permits the in vivo examination of the colorectal pit pattern, which has a high correlation with stereomicroscopic appearances of resected specimens. This new technology may provide an "optical biopsy" which can be used to aid diagnostic precision and guide therapeutic strategies. Conflicting data exist concerning the accuracy of this technique when discriminating neoplastic from non-neoplastic lesions, particularly when flat and depressed.

Aim: To prospectively examine the efficacy of HMCC for the diagnosis of neoplasia in flat and depressed colorectal lesions using standardised morphological, pit pattern, and histopathological criteria. Clinical recommendations for the use of HMCC are made.

Methods: Total colonoscopy was performed on 1850 patients by a single endoscopist from January 2001 to July 2003 using the C240Z magnifying colonoscope. Identified lesions were classed according to the Japanese Research Society guidelines, and pit pattern according to Kudos modified criteria. Pit pattern appearances were then compared with histopathology.

Results: A total of 1008 flat lesions were identified. The sensitivity and specificity of HMCC in distinguishing non-neoplastic from neoplastic lesions were 98% and 92%, respectively. However, when using HMCC to differentiate neoplastic/non-invasive from neoplastic/invasive lesions, sensitivity was poor (50%) with a specificity of 98%. Diagnostic accuracy was not influenced by size or morphological classification of lesions.

Conclusion: HMCC has a high overall accuracy at discriminating neoplastic from non-neoplastic lesions but is not 100% accurate. HMCC is a useful diagnostic tool in vivo but presently is not a replacement for histology. Requirements for further education and training in these techniques need to be addressed.

Figure 1

(A) Focal erythema noted at the mid transverse colon (conventional views). (B) Indigo carmine chromoscopy clearly delineates the circumferential margin of the lesion. The lesion is flat with slight elevation (JRSC IIa). No depressed component is apparent. (C) High magnification chromoscopic colonoscopy (100× magnification) shows a type I pit pattern. The lesion was hyperplastic at histology.

Figure 2

(A) Conventional views of the proximal ascending colon. The vascular net pattern is disrupted with central pallor and peripheral erythema. (B) Indigo carmine chromoscopy applied at the site of subtle mucosal abnormality in the distal ascending colon. A flat type IIb lesion is now well demarcated (non-magnified views). (C) High magnification chromoscopic colonoscopy views (100× magnification). A type IIIL pit pattern is observed. The lesion was an F-type lateral spreading tumour or carpet lesion with low grade dysplasia adenomatous histology.

Figure 3

(A) JRSC type IIa/c (flat elevation with central depression) seen using conventional views in the distal transverse colon. (B) Indigo carmine chromoscopy shows pooling of dye in the area of central depression. (C) Crystal violet chromoscopy at 100× magnification. A type IIIL pattern is seen at the periphery of the lesion with an absent amorphic pit pattern centrally.