Narrow band imaging endoscopy for real-time assessment of duodenal villi

Abstract

The technology of narrow band imaging (NBI) has been available commercially for about a decade. The NBI filter allows only blue and green wavelength of light to pass through and this gives blood vessels a dark appearance [1]. This, along with image magnification and the use of a high definition monitor, allows detailed assessment of the microsurface and microvascularity of the mucosal surface. Accordingly, the information obtained during NBI endoscopy is much more than during conventional white light endoscopy [2]. In the duodenum, villi are clearly seen during magnification NBI endoscopy. Most studies on NBI in the gastrointestinal tract have focussed on the esophagus and colon especially for the evaluation of Barrett's esophagus and detection of colorectal polyps [3,4]. In contrast, relatively little data is available on its utility in assessing duodenal pathology. This technology has been reported to be helpful in assessing ampullary lesions and detecting villous atrophy in the duodenum [5][6][7][8].The study by Goswami et al. published in the current issue of this Journal [9] assesses the role of NBI in predicting duodenal villous morphology. They prospectively enrolled 105 patients with suspected malabsorption and compared the observations made on duodenal villous morphology during NBI endoscopy with histopathology findings. Interestingly, 59 patients had celiac disease or tropical malabsorption and only 1 patient had irritable bowel syndrome (IBS). As chronic diarrhea was one of the inclusion criteria, one would have expected more IBS patients in the study population. Fiftyeight patients had villous atrophy on histology and magnification NBI imaging had 95 % sensitivity and 90.2 % specificity in detecting villous atrophy when interpreted by the person performing the procedure. The endoscopy images were also assessed by another person and they found good interobserver agreement with the primary assessor. The authors have classified the appearance of duodenal villi on magnification NBI into four categories, although this lacked external validation as the authors have mentioned. The appearance of duodenum on NBI endoscopy in patients with normal villi, partially atrophic villi, and completely atrophic villi has been already described in previous studies, and the current study does not provide any additional features for observation [6,7]. However, results from this study are a welcome addition to the data on the usefulness of NBI in duodenal disease.The findings from this study are encouraging and indicate that NBI has a potential role in detecting villous atrophy. A few previously published studies have shown similar results [6,7,10]. Table 1 shows the results of these studies along with data from the current study. All of them show very good sensitivity and specificity of magnification NBI in detecting duodenal villous atrophy. Normal duodenal villi appear finger or leaf-shaped while abnormal villi appear short and stubbed or gyrate or are completely absent. In a clinical setting, this would potentially hel...