Role of Mucosal Protrusion Angle in Discriminating Between True and False Masses of the Small Bowel on Video Capsule Endoscopy

Abstract

The diagnosis of small-bowel tumors is challenging due to their low incidence, nonspecific presentation, and limitations of traditional endoscopic techniques. In our study, we examined the utility of the mucosal protrusion angle in differentiating between true submucosal masses and bulges of the small bowel on video capsule endoscopy. We retrospectively reviewed video capsule endoscopies of 34 patients who had suspected small-bowel lesions between 2002 and 2017. Mucosal protrusion angles were defined as the angle between the small-bowel protruding lesion and surrounding mucosa and were measured using a protractor placed on a computer screen. We found that 25 patients were found to have true submucosal masses based on pathology and 9 patients had innocent bulges due to extrinsic compression. True submucosal masses had an average measured protrusion angle of 45.7 degrees ± 20.8 whereas innocent bulges had an average protrusion angle of 108.6 degrees ± 16.3 (p < 0.0001; unpaired t-test). Acute angle of protrusion accurately discriminated between true submucosal masses and extrinsic compression bulges on Fisher’s exact test (p = 0.0001). Our findings suggest that mucosal protrusion angle is a simple and useful tool for differentiating between true masses and innocent bulges of the small bowel.

Full text

Journal of
Clinical Medicine
Article
Role of Mucosal Protrusion Angle in Discriminating
between True and False Masses of the Small Bowel on
Video Capsule Endoscopy
May Min 1, * , Michael G. Noujaim 2, Jonathan Green 3, Christopher R. Schlieve 3,
Aditya Vaze 4, Mitchell A. Cahan 3and David R. Cave 5
1Department of Internal Medicine, University of Massachusetts Medical School, 55 Lake Ave N.,
Worcester, MA 01655, USA
2Department of Internal Medicine, Duke University School of Medicine, 2301 Erwin Rd,
Durham, NC 27705, USA; mgn9@duke.edu
3Department of Surgery, University of Massachusetts Medical School, 55 Lake Ave N.,
Worcester, MA 01655, USA; jonathan.green@umassmemorial.org (J.G.);
christopher.schlieve@umassmemorial.org (C.R.S.); mitchell.cahan@umassmemorial.org (M.A.C.)
4
Division of Cardiology, University of California Irvine, 333 City Blvd W., Suite 400 Orange, CA 92868, USA;
vazea@uci.edu
5Division of Gastroenterology, University of Massachusetts Medical School, 55 Lake Ave N.,
Worcester, MA 01655, USA; david.cave@umassmemorial.org
*Correspondence: maym522@gmail.com; Tel.: +1-401-330-9702
Received: 19 January 2019; Accepted: 25 March 2019; Published: 27 March 2019


Abstract:
The diagnosis of small-bowel tumors is challenging due to their low incidence, nonspecific
presentation, and limitations of traditional endoscopic techniques. In our study, we examined
the utility of the mucosal protrusion angle in differentiating between true submucosal masses
and bulges of the small bowel on video capsule endoscopy. We retrospectively reviewed video
capsule endoscopies of 34 patients who had suspected small-bowel lesions between 2002 and 2017.
Mucosal protrusion angles were defined as the angle between the small-bowel protruding lesion and
surrounding mucosa and were measured using a protractor placed on a computer screen. We found
that 25 patients were found to have true submucosal masses based on pathology and 9 patients had
innocent bulges due to extrinsic compression. True submucosal masses had an average measured
protrusion angle of 45.7 degrees
±
20.8 whereas innocent bulges had an average protrusion angle of
108.6 degrees
±
16.3 (p< 0.0001; unpaired t-test). Acute angle of protrusion accurately discriminated
between true submucosal masses and extrinsic compression bulges on Fisher’s exact test (p= 0.0001).
Our findings suggest that mucosal protrusion angle is a simple and useful tool for differentiating
between true masses and innocent bulges of the small bowel.
Keywords: small-bowel mass; small-bowel bulge; video capsule endoscopy
1. Introduction
The diagnosis of small-bowel tumors is challenging due to their low incidence, nonspecific clinical
presentation, and the limitations of traditional endoscopic techniques. Video capsule endoscopy (VCE)
has dramatically improved our ability to detect small-bowel tumors by enabling the visualization
of portions of the small-bowel that are not accessible by colonoscopy or upper endoscopy [
1
]. VCE
was able to diagnose small-bowel tumors in 8.9% of the 562 patients in a single-center retrospective
study who underwent VCE for occult gastrointestinal bleeding, abdominal pain, and a variety of other
J. Clin. Med. 2019,8, 418; doi:10.3390/jcm8040418 www.mdpi.com/journal/jcm

J. Clin. Med. 2019,8, 418 2 of 8
indications [
2
]. Furthermore, VCE missed only 10% of small-bowel tumors compared to a collective
miss rate of 73% by double balloon enteroscopy, small-bowel series, colonoscopy, and ileoscopy [3].
One of the major limitations of VCE is its inability to biopsy lesions identified during passage
through the small bowel. Though double balloon enteroscopy can potentially be used to visualize the
entire small intestine, reported rates for total enteroscopy are widely variable (ranging between 20 and
90%) and are highly user-dependent [
1
]. A group of experts at the 2006 International Conference on
Capsule Endoscopy identified several major and minor characteristics of small-bowel lesions that are
predictive of tumors, including mucosal disruption, bleeding, irregular surface, polypoid appearance,
color, delayed passage, white villi, and invagination [
4
]. However, in the absence of these features,
it can be challenging to differentiate between true submucosal masses and benign bulges arising from
extrinsic compression by adjacent structures.
In order to address this challenge, Girelli et al. developed the “smooth, protruding lesions
index at capsule endoscopy” (SPICE) and examined its utility through a single-center, prospective
study of
25 patients [5]
. SPICE score was calculated by adding one point for each of the following:
(1) Well-defined boundary with surrounding mucosa, (2) diameter less than height, (3) visible lumen,
and (4) image of lesion lasting more than 10 min. A SPICE score >2 was found to be 83.3% sensitive
and 89.4% specific for identifying true submucosal masses, therefore supporting a novel system for
differentiating true from false masses on VCE. Through our retrospective study, we will evaluate the
utility of an additional morphologic criterion, the mucosal protrusion angle. We have defined this
as the angle between the small-bowel protruding lesion and surrounding mucosa. We hypothesize
that false masses arising from extrinsic compression will create more obtuse protrusion angles
>90◦
compared with true submucosal masses, <90
◦
. By determining the utility of the mucosal protrusion
angle, we hope to increase the specificity and sensitivity of VCE for detecting submucosal masses of
the small bowel.
2. Experimental Section
2.1. Study Design
Patient demographics, indication for VCE, findings on VCE, radiographic studies, endoscopic
and surgical interventions, pathology results, and survival following VCE were all collected
retrospectively. Only those patients who were found to have a small-bowel protruding lesion on
VCE were included in the study. Small-bowel protruding lesions were defined as any masses seen
on VCE, including suspected submucosal masses and benign bulges. In total, we analyzed the
VCEs of 34 patients. All VCEs were performed with the M2 A, PillCam
TM
SB2 or SB3 (Medtronic,
Minneapolis, MN, United States) and were analyzed using RAPID
TM
version 8.3 (Given Imaging LTD,
Yoqneam, Israel). This study was approved by the UMass Medical School Institutional Review board
on December 2, 2015.
2.2. Angle Measurement
All angles were obtained through VCE images on RAPID
TM
software version 8.3 (Given Imaging
LTD, Yoqneam, Israel). The mucosal protrusion angle was defined as the angle between the protruding
lesion and surrounding mucosa. Mucosal protrusion angles were measured using a protractor placed
on the computer screen. We categorized lesions as having a protrusion angle of either >90
◦
or <90
◦
and hypothesized that an angle >90
◦
suggests an external protrusion or bulge while an angle <90
◦
suggests a submucosal mass. The frame for protrusion angle measurement was selected independently
at each user’s discretion based on the frame in which they felt the protrusion angle could best be
measured. A sample image with angle measurement technique was provided to each operator
(see Figure 1). Angles were measured independently by two novice users and one expert user to assess
for interobserver agreement. Both novice users performed <10 VCEs prior to this study and the expert
user performed >1000 VCEs.

J. Clin. Med. 2019,8, 418 3 of 8
J. Clin. Med. 2019, 8, x FOR PEER REVIEW 3 of 8
(a)
(b)
Figure 1. (a) Demonstration of acute angle measurement on RAPIDTM. (b) Demonstration of obtuse
angle measurement on RAPIDTM.
2.3. SPICE Calculation
SPICE scores were calculated for each patient as outlined in Girelli et al. [5]. Lesions were given
1 point for the following: (1) Sharp boundary with surrounding mucosa, (2) height larger than
diameter, (3) visible lumen in the frames in which the lesion appears, and (4) image of the lesion
lasting more than 10 minutes. Any lesion with greater than two of the four SPICE criteria were
predicted to be true submucosal masses per the findings in Girelli et al. A ruler placed directly on the
computer screen was used to determine exact height and diameter of the small-bowel lesions.
2.4. Statistics
We calculated the sensitivity, specificity, positive predictive value (PPV), and negative
predictive value (NPV) of both SPICE and protrusion angle. Fisher’s Exact Test was performed to
assess the association between protrusion angle and true vs. false submucosal mass. All Fisher’s tests
were one-tailed and the cutoff for significance was set at a p-value of <0.05. Interobserver agreement
(kappa statistic) was assessed by comparing angle measurements of two novice VCE users and an
expert user. We ran a logistic regression on capsule angle measurements for expert and novice users
combined using a cutoff value of <90 degrees for a true mass and fit the data to a receiver operating
characteristic (ROC) curve. We also ran a logistic regression on SPICE scores using a cutoff of >2 for
true mass and fit the data to an ROC curve. Statistical analysis was performed using Stata Statistical
Software: Release 13 (College Station, TX, USA).
3. Results
3.1. Demographics
We retrospectively reviewed the charts of 289 patients over the age of 18 who had undergone
VCE for suspected small-bowel protruding lesions between January 2002 and March 2017. Of the
patients, 241 were excluded because no protruding lesion was identified between the pylorus and
ileocecal valve. Five patients were excluded because they were later identified as having true
submucosal masses but did not have available pathology reports in our medical records. Nine
patients were excluded because either the protrusion angle or SPICE score could not be determined
due to poor image quality or limited visualization of the protruding lesion. In total, we analyzed the
Figure 1.
(
a
) Demonstration of acute angle measurement on RAPID
TM
. (
b
) Demonstration of obtuse
angle measurement on RAPIDTM.
2.3. SPICE Calculation
SPICE scores were calculated for each patient as outlined in Girelli et al. [
5
]. Lesions were given
1 point for the following: (1) Sharp boundary with surrounding mucosa, (2) height larger than diameter,
(3) visible lumen in the frames in which the lesion appears, and (4) image of the lesion lasting more
than 10 min. Any lesion with greater than two of the four SPICE criteria were predicted to be true
submucosal masses per the findings in Girelli et al. A ruler placed directly on the computer screen was
used to determine exact height and diameter of the small-bowel lesions.
2.4. Statistics
We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive
value (NPV) of both SPICE and protrusion angle. Fisher’s Exact Test was performed to assess the
association between protrusion angle and true vs. false submucosal mass. All Fisher’s tests were
one-tailed and the cutoff for significance was set at a p-value of <0.05. Interobserver agreement
(kappa statistic) was assessed by comparing angle measurements of two novice VCE users and
an expert user. We ran a logistic regression on capsule angle measurements for expert and novice users
combined using a cutoff value of <90 degrees for a true mass and fit the data to a receiver operating
characteristic (ROC) curve. We also ran a logistic regression on SPICE scores using a cutoff of >2 for
true mass and fit the data to an ROC curve. Statistical analysis was performed using Stata Statistical
Software: Release 13 (College Station, TX, USA).
3. Results
3.1. Demographics
We retrospectively reviewed the charts of 289 patients over the age of 18 who had undergone VCE
for suspected small-bowel protruding lesions between January 2002 and March 2017. Of the patients,
241 were excluded because no protruding lesion was identified between the pylorus and ileocecal
valve. Five patients were excluded because they were later identified as having true submucosal
masses but did not have available pathology reports in our medical records. Nine patients were
excluded because either the protrusion angle or SPICE score could not be determined due to poor
image quality or limited visualization of the protruding lesion. In total, we analyzed the VCEs of

J. Clin. Med. 2019,8, 418 4 of 8
34 patients. The average age was 73.0
±
16.6 years. There was a larger proportion of female patients
(67.6%) compared with male patients (32.4%) (see Table 1)
Table 1. Patient Characteristics.
Gender Age Indication Novice
Angle b
Expert
Angle Location Imaging cEndoscopy cSurgery Final Diagnosis
F 65 OGB 42.5 20.0 Jejunum CTE + ASBE + Yes GIST
M 52 OGB 16.0 10.0 Ileum CT + ASBE + Yes GIST
M 81 OGB 50.0 30.0 Ileum CT −ASBE −Yes Carcinoid
F 56 Carcinoid a20.0 10.0 Ileum CT ±Colo + Yes Carcinoid
F 77 IDA 27.5 20.0 Ileum CT −RSBE + Yes Carcinoid
F 56 CD 55.0 50.0 Ileum CTE ±RSBE + Yes Carcinoid
F 58 AP 10.0 20.0 Ileum CT ±Colo + Yes Carcinoid
F 62 AP 100.0 10.0 Ileum CT + Colo −Yes Carcinoid
M 38 AP 72.5 30.0 Jejunum CT + ASBE −Yes Inflammatory
Polyp
F 73 OGB 35.0 110.0 Jejunum ND ASBE + No Lymphangiectasia
M 53 OGB 25.0 30.0 Ileum CT −Colo −Yes DLBCL
F 30 Peutz-Jeghers a45.0 30.0 Jejunum ND RSBE + Yes Peutz-Jeghers
F 39 Peutz-Jeghers a47.5 30.0 Ileum ND RSBE + No Peutz-Jeghers
F 36 Peutz-Jeghers a45.0 50.0 Duodenum ND ASBE + Yes Peutz-Jeghers
M 37 IDA 27.5 40.0 Jejunum ND ASBE + Yes Peutz-Jeghers
F 49 OGB 50.0 20.0 Jejunum ND ASBE + No Peutz-Jeghers
F 58 OGB 52.5 15.0 Jejunum CT −ASBE + No Inflammatory
Polyp
M 37 Crohn’s a65.0 20.0 Jejunum CT −ASBE + No Inflammatory
Polyp
F 76 OGB 40.0 40.0 Jejunum CTE + ASBE + Yes Hamartoma
F 57 OGB 45.0 10.0 Duodenum ND ASBE + No Hamartoma
M 78 BO 60.0 20.0 Ileum MRE ±ASBE −Yes Lipoma
F 83 AP 82.5 >90 Duodenum ND ASBE + No Tubular Adenoma
F 41 OGB 35.0 10.0 Ileum ND Colo −Yes Leiomyoma
F 48 OGB 47.5 10.0 Jejunum ND ASBE −Yes Hemangioma
M 47 AP 30.0 60.0 Duodenum CT + ASBE + No
Hyperplastic Polyp
F 70 AP, OGB 130.0 70.0 Jejunum CT −ASBE −No Bulge
M 51 Leukemia a95.0 50.0 Jejunum PET CT + NA No Bulge
F 61 AP/CD 115.0 20.0 Duodenum ND ND No Bulge
F 29 AP 105.0 110.0 Ileum CT −Colo −No Bulge
F 55 OGB 75.0 20.0 Jejunum NA NA No Bulge
M 85 AP 122.5 130.0 Ileum ND Colo −No Bulge
M 29 AP 105.0 30.0 Ileum CT −Colo −No Bulge
F 54 OGB 125.0 130.0 Ileum CT −Colo −No Bulge
F 73 IDA 102.5 130.0 Ileum CT −ASBE −No Bulge
AP, abdominal pain; ASBE, anterograde small-bowel enteroscopy; BO, bowel obstruction; CD, chronic diarrhea;
Colo, colonoscopy; CT, CT abdomen/pelvis; CTE, CT enterography; DLBCL, diffuse large B cell lymphoma; GIST,
gastrointestinal stromal tumor; IDA, iron deficiency anemia; MRE, magnetic resonance enterography; NA, not
available; ND, not done; OGB, obscure gastrointestinal bleeding; PET CT, positron emission tomography CT; RSBE,
retrograde small-bowel enteroscopy.
a
Video capsule endoscopy performed for screening or surveillance.
c
Novice
angle represents an average of measurement of 2 novice users.
b
Signs (+), (
−
), and (
±
) indicate positive, negative,
and equivocal findings, respectively.
3.2. Diagnosis
The most common indication for VCE was obscure gastrointestinal bleeding (41.2%), followed
by abdominal pain (29.4.%). Twenty-five patients were found to have true submucosal masses based
on pathology report (6 carcinoid, 2 gastrointestinal stromal tumor, 1 diffuse large B-cell lymphoma,
1 leiomyoma, 5 Peutz-Jeghers, 1 tubular adenoma, 1 hyperplastic polyp, 3 inflammatory polyps,
2 hamartomas, 1 lipoma, 1 cavernous hemangioma, 1 lymphangiectasia) and 9 patients had innocent

J. Clin. Med. 2019,8, 418 5 of 8
bulges due to extrinsic compression (see Table 1). None of the patients with bulges had available
pathology data because no mass was seen on follow-up studies such as enteroscopy or repeat
capsule endoscopy.
3.3. Protrusion Angle and SPICE Calculations
True submucosal masses had an average measured angle of protrusion of 45.7
◦±
20.80 whereas
innocent bulges had an average protrusion angle of 108.6
◦±
16.3
◦
(p< 0.0001; unpaired t-test).
When compared with SPICE scores, a mucosal protrusion angle <90
◦
had a higher sensitivity
(
92.0% vs. 32.0%
), PPV (96.0% vs. 88.9%), and NPV (66.7% vs. 32.0%). Both protrusion angle and
SPICE scores had the same specificity of 88.9%. Acute angle of protrusion accurately discriminated
between true submucosal masses and extrinsic compression bulges on Fisher’s exact test (p= 0.0001).
Interobserver agreement between the two novice users and the expert user was good (
κ
= 0.67; 95% CI,
0.50–0.84). The area under the curve for mass angle using a cutoff value of <90 degrees for true mass
was 0.93. The area under the curve for SPICE scores using a cutoff value of >2 for true mass was 0.55
(see Figure 2).
J. Clin. Med. 2019, 8, x FOR PEER REVIEW 5 of 8
3.2. Diagnosis
The most common indication for VCE was obscure gastrointestinal bleeding (41.2%), followed
by abdominal pain (29.4.%). Twenty-five patients were found to have true submucosal masses based
on pathology report (6 carcinoid, 2 gastrointestinal stromal tumor, 1 diffuse large B-cell lymphoma,
1 leiomyoma, 5 Peutz-Jeghers, 1 tubular adenoma, 1 hyperplastic polyp, 3 inflammatory polyps, 2
hamartomas, 1 lipoma, 1 cavernous hemangioma, 1 lymphangiectasia) and 9 patients had innocent
bulges due to extrinsic compression (see Table 1). None of the patients with bulges had available
pathology data because no mass was seen on follow-up studies such as enteroscopy or repeat capsule
endoscopy.
3.3. Protrusion Angle and SPICE Calculations
True submucosal masses had an average measured angle of protrusion of 45.7° ± 20.80 whereas
innocent bulges had an average protrusion angle of 108.6° ± 16.3° (p < 0.0001; unpaired t-test). When
compared with SPICE scores, a mucosal protrusion angle <90° had a higher sensitivity (92.0% vs.
32.0%), PPV (96.0% vs. 88.9%), and NPV (66.7% vs. 32.0%). Both protrusion angle and SPICE scores
had the same specificity of 88.9%. Acute angle of protrusion accurately discriminated between true
submucosal masses and extrinsic compression bulges on Fisher’s exact test (p = 0.0001). Interobserver
agreement between the two novice users and the expert user was good (κ = 0.67; 95% CI, 0.50–0.84).
The area under the curve for mass angle using a cutoff value of <90 degrees for true mass was 0.93.
The area under the curve for SPICE scores using a cutoff value of >2 for true mass was 0.55 (see Figure
2).
(a)
(b)
Figure 2.
(
a
) The area under the receiver operating characteristic (ROC) curve for combined expert and
novice mucosal protrusion angle using a cutoff of <90
◦
for true mass. (
b
) The area under the ROC curve
for smooth, protruding lesion at capsule endoscopy (SPICE) index using a cutoff of >2 for true mass.

J. Clin. Med. 2019,8, 418 6 of 8
4. Discussion
VCE has emerged as a convenient way to identify small-bowel tumors because it is non-invasive
and allows for visualizuation of the entire length of the small bowel. Over the past several decades,
its role in detecting malignancies has become more important as the incidence of small-bowel tumors
has increased from 11.8 cases per million in 1973 to 22.7 cases per million in 2004. It is unclear how
much of this increase can be attributed to improved diagnosis with the advent of VCE, however
Bilimora et al. pointed to the rising incidence of carcinoid tumors as a major driving factor [
6
].
Prior studies have cited VCE malignant tumor detection rates as high as 63–83% [
7
,
8
]. In our study,
we found a lower but still significant proportion of malignant tumors (45% of true submucosal masses)
after excluding patients with Peutz-Jehgers.
Though VCE has significantly improved our ability to detect small-bowel tumors, it has also
opened up what Pennazio et al. describes as a “Pandora’s box” of findings including both malignant
and benign lesions [
9
]. Bulges are among one of the most problematic benign findings on VCE, as they
can often mimic the appearance of small-bowel tumors and contribute to false-positive outcomes [
10
].
False-positive outcomes may lead to further invasive and costly procedures, therefore highlighting
the importance of differentiating bulges from true submucosal masses. Though “alarm” features,
including bleeding, mucosal disruption, irregular surface, polypoid appearance, and white villi,
have been described based upon expert consensus for malignant small-bowel masses, there are few
studies available to support the use of these findings on VCE [
4
,
11
]. There have been prior attempts
to use of automatic detection methods based on textural alterations on VCE, however none of these
methods have been validated in clinical practice for diagnosing submucosal masses [12,13].
The SPICE score described by Girelli et al. was the first scoring system developed to distinguish
between submucosal masses and bulges on VCE [
5
]. This study showed that a SPICE score >2 was
highly sensitive (83.3%) and specific (89.4%) for detection of true submucosal masses. A validation
study by Rodrigues et al. showed a lower sensitivity (66.7%) but high specificity (100.0%) for the
SPICE score [
14
]. In our study, we found that a SPICE score >2 had an equally high specificity
when compared with the mucosal protrusion angle but a significantly lower sensitivity of 32.0%.
The discrepencies in our results may in large part be due to differences in study design, as the
Girelli et al. study
was prospective whereas ours was retrospective. Additionally, we included patients
with Peutz-Jehgers and patients with “alarm” features outlined by Shyung et al., all of whom were
excluded
by Girelli et al. [5,11]
. None of our true masses had a length time >10 min, criteria 4 on the
SPICE scale, which made SPICE less sensitive in our patient population.
We evaluated the utililty of a new, simpler measure, the mucosal protrusion angle, in differentiating
true masses from bulges. We found that an angle <90
◦
accurately discriminated between true masses
and extrinsic compression bulges (p= 0.0001). Acute protrusion angle also had a high sensitivity (92.0%)
and specificity (88.9%) for distinguishing between true masses and bulges. It should be noted that we
used both novice and expert users in our study, whereas the Girelli et al. study utilized only expert users.
Discrepencies in angle measurements between the novice and expert users in our study were likely due
to differences in the frames of the lesion on RAPID
TM
chosen by each user. Despite these discrepencies,
we found that there was good interobserver agreement between the novice and expert users when using
mucosal protrusion angle (
κ
= 0.67; 95% CI, 0.50–0.84). This suggests that mucosal protrusion angle has the
potential to be utilized by a wide range of users regardless of their VCE experience level.
5. Study Limitations
There are several limitations of this study that are important to note. First, this is a retrospective
study and therefore is subject to both confounding and selection bias. As mentioned above, one
potential source of bias is the variation in frame selection on VCE, as there was no way to ensure that
all users would select the same image for angle measurement. In the future, it would be valuable
to assess the degree of variability in frame selection between observers as this was not evaluated in
our present study. An additional limitation of our study was that none of the bulges had pathologic

J. Clin. Med. 2019,8, 418 7 of 8
confirmation due to our inability to visualize these transient lesions on subsequent interventions
and the unethical nature of performing surgery or further invasive workup in such patients. We felt
that long-term follow up provided an adequate surrogate but recognize this as a limitation. Finally,
the number of patients in our study is comparatively small.
6. Conclusions
Mucosal protrusion angle is a novel and simple tool for differentiating between true masses
and innocent bulges of the small bowel. To our knowledge, there are no prior studies examining the
utility of this index. We found that small-bowel protruding lesions with a protrusion angle >90
◦
are
more likely to represent bulges and may not warrant any additional workup, whereas lesions with
angle <90◦
are more likely to be true masses that should be evaluated for malignancy with enteroscopic
or surgical interventions. Further prospective studies are still needed to validate our results.
Author Contributions:
Conceptualization, D.R.C., M.M. and M.G.N.; methodology, D.R.C., M.M. and M.G.N.;
validation, D.R.C., M.M., and M.G.N.; formal analysis, M.M., M.G.N., J.G., and A.V.; investigation, M.M., M.G.N.,
J.G., and C.R.S.; resources, M.M. and M.G.N.; writing—original draft preparation, M.M.; writing—review and
editing, D.R.C., M.M., and M.G.N.; visualization, M.M. and M.G.N.; supervision, D.R.C. and M.A.C.; project
administration, D.R.C. and M.M.
Conflicts of Interest:
David R. Cave has a research grant with Olympus Corporation and is a clinical trial
investigator for Medtronics. Olympus Corporation and Medtronics had no role in the design of the study; in the
collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the
results. The other remaining authors have no conflicts of interest to declare.
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