Published online Jan 28, 2019. doi: 10.3748/wjg.v25.i4.498
Peer-review started: September 30, 2018
First decision: November 15, 2018
Revised: December 3, 2018
Accepted: December 19, 2018
Article in press: December 20, 2018
Published online: January 28, 2019
Processing time: 118 Days and 16.6 Hours
Esophageal lesions are traditionally described according to the distance from the incisors. This measure, while helpful in roughly describing large lesions, lacks radial orientation and is inaccurate for the precise location of dysplastic lesions and small flat tumors. Furthermore, commonly used esophageal divisions comprising cervical, thoracic, and abdominal segments are unrecognized during an upper GI examination, making this surgical division meaningless for endoscopists. As esophageal endoluminal anatomy has been poorly studied, current endoscopy practice lacks these essentials; offering vague lesion identification to a second intervening endoscopist.
Although anatomical and cross-sectional radiological studies, have identified two esophageal landmarks, the left main bronchus and the left atrium, and revealed their anterior location to the esophagus, the long tubular esophageal shape has limited our ability to accurately orientate and assess the location of esophageal lesions. Even though we have postulated that these landmarks can be used to divide the esophageal length into three sections as part of the upper systematic alphanumeric coded endoscopic approach, an endoluminal study characterizing these landmarks has never been reported.
Our study aimed to determine the frequency of these landmarks, distance from the incisors and their quadrant orientation using white light endoscopy, and to confirm these findings by endoscopic ultrasound (EUS).
Quadrant orientation and distance from the incisors were estimated in 207 consecutive patients using white light examination. A sub-study was also performed using white light followed by EUS in 25 consecutive patients to confirm the findings. Once in the esophageal lumen, the endoscope was oriented with the left esophageal quadrant between 6 and 9 o’clock. This position was confirmed as follows: with the patient in the left lateral position, 3 mL of 0.25% Indigo Carmine was poured into the esophageal lumen using an irrigation catheter. Utilizing gravity, the pooled water identified the left quadrant of the esophageal circumference. By positioning the left quadrant between 6 and 9 o’clock as previously mentioned, the other three quadrants were defined as follows: Anterior quadrant: the portion of the circumference between 9 and 12 o’clock; Right quadrant: the portion of the circumference contralateral to the left quadrant and located between 12 and 3 o’clock; Posterior quadrant: portion of the circumference contralateral to the anterior quadrant and located between 3 and 6 o’clock. This esophageal orientation was defined as the natural axis and was maintained throughout the exam. After identifying the radial orientation of the landmark, the distance from the incisors was estimated using the standard demarcation of the endoscope located every 5 cm as a primary reference, and finally, for precise estimation, a flexible ruler marked in millimeters was positioned between the incisors and the closest endoscope mark.
The left main bronchus and left atrium esophageal landmarks were identified using white light in 99% and 100% of subjects at a mean distance of 25.8 cm (SD 2.3), and 31.4 cm (SD 2.4) from the incisors, respectively. The left main bronchus landmark was found to be a tubular, concave, non-pulsatile, esophageal external compression, occupying approximately 1/4 of the circumference. The left atrium landmark was identified as a round, convex, pulsatile, esophageal external compression, occupying approximately 1/4 of the circumference. Both landmarks were identified using white light on the anterior esophageal quadrant. In the sub-study, the left main bronchus was identified in 24 (92%) patients at 25.4 cm (SD 2.1) and 26.7 cm (SD 1.9) from the incisors, by white light and EUS, respectively. The left atrium was recognized in all patients at 30.5 cm (SD 1.9), and 31.6 cm (SD 2.3) from the incisors, by both white light and EUS, respectively. EUS confirmed that the landmarks corresponded to these two structures, respectively, and that they were located on the anterior esophageal wall. The Bland-Altman plot demonstrated high agreement between the white light and EUS measurements.
Although these endoscopic measurements require further inter-observer validation studies, this study provides an endoscopic characterization of esophageal landmarks corresponding to the left main bronchus and left atrium, to permit radial and longitudinal orientation and accurate lesion location.
Endoscopic recognition of these two landmarks may have different clinical applications. First, when taken together along with the cricopharyngeal narrowing and the esophagogastric (EG) junction landmarks, these constitute the fundamentals for the systematic alphanumeric endoscopic proposal to evaluate the esophagus, and can be used, as reported by us, to improve longitudinal orientation by dividing the esophagus into three non-equal, but practical endoscopic sections: the upper third, located between the cricopharyngeal narrowing and the left main bronchus; the middle third, located between the left main bronchus and the left atrium; and the distal third, extending from the left atrium downward to the EG junction. The potential usefulness of this endoscopic classification requires further study, but currently provides clinically relevant data to fulfill published guidelines by major gastroenterology societies, which recommend accurate photo documentation of endoscopic landmarks and a careful description of the location of a lesion to allow subsequent therapeutic applications and future surveillance. Second, appropriate recognition of the main left bronchus and/or the left atrium landmarks and their anterior location to the esophagus, may significantly improve radial quadrant orientation for both standardization of anterior or posterior approaches in POEM procedures, and precise localization of Barrett’s esophagus with dysplasia and small squamous cell carcinomas. Furthermore, after identification of the left esophageal quadrant as described herein, these landmarks can potentially be used to properly distinguish the 4-quadrants in any esophageal portion including the EG junction. When accurate radial orientation is achieved, a clock face-distribution can be used to precisely locate any abnormalities in the esophageal circumference.