Endoscopic examination of the papilla: to cap or swap the scope?

“The real voyage of discovery consists, not in seeking new landscapes, but in having new eyes”.

Marcel Proust, in “Remembrance of Things Past”.

Standard esophagogastroduodenoscopy (S-EGD) with a forward-viewing endoscope has become an established, highly efficient procedure for examining the upper digestive tract. However, S-EGD has a limited role in offering a complete assessment of the major duodenal papilla (MDP), which is due to the tangential position of the MDP and the presence of duodenal folds, as well as occasionally to a periampullary diverticulum [1]. On the other hand, a thorough examination of the MDP is essential for the early detection of ampullary and periampullary lesions in high risk patients (for example, those with familial polyposis syndromes) and for surveillance after previous endoscopic resection of an ampullary tumor, as well as in patients who have a dilatation of the common bile duct or the main pancreatic duct, or recurrent acute pancreatitis of unclear etiology [2]. In these cases, a side-viewing endoscope is recommended [1]; nevertheless, side-viewing endoscopes are not widely available and their use requires specific experience [2].

Cap-assisted EGD (C-EGD) involves attaching a transparent cap to the tip of a forward-viewing endoscope. The cap, which protrudes for about 4 mm outside the endoscope, helps to flatten the duodenal folds, and therefore to identify and expose the MDP while keeping an adequate distance to maintain the focus and prevent loss of visualization [3]. A recent, randomized, blinded, controlled, crossover study, including 101 patients scheduled for upper gastrointestinal (GI) endoscopy, which compared C-EGD with S-EGD revealed that C-EGD allowed complete examination of the MDP in 97 % of the patients vs. 24 % with S-EGD [2]. The authors concluded that C-EGD could increase the diagnostic yield in this setting and could be incorporated in routine clinical practice.

In this issue of Endoscopy, the results of two comparative studies focusing on the use of C-EGD are presented [4] [5]. Both are well designed, with sound methodology, albeit with contradictory results.

“Cap-assisted esophagogastroduodenoscopy allows optimal examination of the upper digestive tract, including complete visualization of the major duodenal papilla, as well as detailed mucosal assessment, which is not the case for side-viewing duodenoscopy.”

The first study, conducted by the same group that had published the aforementioned randomized trial on C-EGD [2], was a prospective, randomized, blinded, controlled, noninferiority crossover study, which included patients scheduled for routine upper GI endoscopy [4]. Patients were randomized to undergo either side-viewing duodenoscopy followed by C-EGD (group A), or C-EGD followed by side-viewing duodenoscopy (group B). Photos were taking during the procedures to be evaluated by external experts, after digitally processing them to hide the cap and render the type of endoscope unrecognizable. A scoring system was applied, which included the quality of examination of the papilla (0 – 3, where 3 meant the whole MDP was visualized); the assessment of the mucosal pattern (1 – 10, where 10 meant excellent); the ability to visualize the periampullary area (1 – 10); and the overall satisfaction rate (1 – 10).

A total of 62 patients were enrolled and the duodenum was intubated in all of them. Complete visualization of the MDP (score 3) was achieved in 60/62 examinations by side-viewing duodenoscope and in 59/62 by C-EGD (97 % vs. 95 %). C-EGD seemed to provide a better assessment of the mucosal pattern, whereas the side-viewing endoscope provided a better visualization of the periampullary area. There was no significant difference with regard to the duration of each type of procedure and no complications were noted. Therefore, the authors concluded that C-EGD could be used as a substitute to side-viewing duodenoscopy to examine the MDP.

The second study was also a prospective, randomized, noninferiority trial, which included patients scheduled for endoscopic retrograde cholangiopancreatography (ERCP) who were randomized to undergo C-EGD or side-viewing duodenoscopy [5]. Visualization of the MDP was assessed by the same score (0 – 3), as previously reported. A total of 171 patients were allocated to C-EGD (n = 85) or side-viewing duodenoscopy (n = 86). Complete examination of the MDP was achieved in 68.2 % of patients (58/85) in the C-EGD group and 86.0 % (74/86) in side-viewing duodenoscopy group. Moreover, the time taken to examine the MDP was significantly longer with C-EGD. Therefore, the authors concluded that C-EGD could not replace side-viewing duodenoscopy for examination of the MDP.

How can we explain such contradictory results? Both studies used high resolution endoscopes and the same scoring system for MDP visualization, as well as similar types of 4-mm caps for C-EGD. Nevertheless, we can underline three major differences.

First, the patient populations were different: patients scheduled for routine upper GI endoscopy in the study by Abdelhafez et al. [4] and patients scheduled for ERCP in the study by Shi et al. [5]. Patients in the first study were younger with symptoms such as reflux and dyspepsia, in contrast to patients who were older with biliary stones in the second study. Periampullary diverticula were identified in 18/171 of the patients (10.5 %) in the second study, which hindered complete MDP examination with C-EGD.

Second, the procedures in the study by Abdelhafez et al. were performed with the patients under deep sedation with propofol, whereas conscious sedation with midazolam and pethidine was given to the patients in the study of Shi et al., which could influence the quality of the examination.

Finally, a potential factor that could interfere with performance was the operators’ experience: in the study by Abdelhafez et al., the two operators had a threshold of > 1600 ERCPs and > 100 C-EGDs, while in the study of Shi et al., the threshold for the four operators was > 1000 ERCPs and > 10 C-EGDs.

Despite the divergent results, it can still be concluded that C-EGD may be a useful addition to our toolbox for high risk patients undergoing routine upper GI endoscopy. C-EGD allows optimal examination of all of the upper digestive tract, including complete visualization of the MDP, as well as detailed mucosal assessment, which is not the case for side-viewing duodenoscopy. Moderate experience is required to perform C-EGD, but the learning curve is easy and most endoscopists should be capable of successfully performing C-EGD, irrespective of their ERCP experience [6]. On the other hand, for patients scheduled for therapeutic procedures such as ERCP or endoscopic papillectomy, in whom optimal examination of the periampullary area, as well as the MDP, is essential, the use of a side-viewing endoscope is sufficient and C-EGD probably has no added value.

In conclusion, C-EGD can be of additional value for screening in routine upper GI endoscopy in patients at high risk of MDP lesions. Nevertheless, these findings have to be confirmed in larger trials, including in patients in whom the procedures are performed without sedation.

• References

• 1 Chathadi KV, Khashab MA. ASGE Standards of Practice Committee. et al. The role of endoscopy in ampullary and duodenal adenomas. Gastrointest Endosc 2015; 82: 773-781
• 2 Abdelhafez M, Phillip V, Hapfelmeier A. et al. Cap assisted upper endoscopy for examination of the major duodenal papilla: a randomized, blinded, controlled crossover study (CAPPA Study). Am J Gastroenterol 2017; 112: 725-733
• 3 Choi YR, Han JH, Cho YS. et al. Efficacy of cap-assisted endoscopy for routine examining the ampulla of Vater. World J Gastroenterol 2013; 19: 2037-2043
• 4 Abdelhafez M, Phillip V, Hapfelmeier A. et al. Comparison of cap-assisted endoscopy vs. side-viewing endoscopy for examination of the major duodenal papilla: a randomized, controlled, non-inferiority crossover study. Endoscopy 2019; 51: 419-426
• 5 Shi X, Luo H, Ning B. et al. Effect of cap-assisted esophagogastroduodenoscopy on examination of the major duodenal papilla: a non-inferior, randomized controlled trial. Endoscopy 2019; 51: 427-435
• 6 Kallenberg FG, Bastiaansen BA, Dekker E. et al. Cap-assisted forward-viewing endoscopy to visualize the ampulla of Vater and the duodenum in patients with familial adenomatous polyposis. Endoscopy 2017; 49: 181-185