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© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Ultrasound features and the diagnostic strategy of subhepatic
appendicitis
Dong Yu1#, Chenyao Gu2#, Shuchen Zhang2, Hui Yang3, Taotao Yao4
1Department of Radiology, Jizhong Energy Fengfeng Group Hospital, Handan, China; 2Department of Radiology, Yancheng No. 1 People’s
Hospital, Yancheng, China; 3Department of Orthopaedic, Jizhong Energy Fengfeng Group Hospital, Handan, China; 4Rehabilitation Center, the
First Afliated Hospital of Guangzhou University of Traditional Chinese Medicine, Guangzhou, China
Contributions: (I) Conception and design: D Yu; (II) Administrative support: S Zhang; (III) Provision of study materials or patients: C Gu; (IV)
Collection and assembly of data: H Yang; (V) Data analysis and interpretation: T Yao; (VI) Manuscript writing: All authors; (VII) Final approval of
manuscript: All authors.
#These authors contributed equally to this work.
Correspondence to: Dr. Shuchen Zhang. Department of Radiology, Yancheng No. 1 People’s Hospital, 166 Yulong Road, Tinghu District, Yancheng,
China. Email: 2220099999@qq.com.
Background: This study aimed to compare the differences of ultrasound findings between subhepatic
appendicitis and appendicitis at a normal position, then discuss the diagnostic strategies and improve the
accuracy of diagnosis.
Methods: A retrospective analysis was performed in our hospital. One thousand five hundred ninety-
one patients with appendicitis were diagnosed from January 2014 to January 2018. Eighteen patients with
subhepatic appendicitis and 25 patients with appendicitis with regular positions were selected randomly as
the control group. The difference in ultrasound features between the two groups was studied. Comparisons
between the two groups showed statistically significant differences in the frequencies of the fishbone sign,
enlarged appendix, appendicoliths, and hyperechoic omental cap (P<0.05).
Results: Statistical significance was not observed with the difference in the frequency of whether there was
lymphadenectasis (P>0.05) in the abdominal cavity between the two groups. The Pareto chart was drawn
to look for the main factors associated. The results of interpretation on the critical points of diagnosis for
subhepatic appendicitis: (I) the fishbone sign of a dilated ileum in the right lower abdomen; and (II) the
fishbone sign of a dilated ileum in the right lower abdomen + presence of an enlarged appendix in the right
upper abdomen.
Conclusions: An abnormally dilated ileum in the right lower abdomen – the fishbone sign, is a vital sign leading
to the diagnosis of subhepatic appendicitis. The fishbone sign of a dilated ileum in the right lower abdomen +
whether there is a vermiform structure is an important diagnostic indicator for subhepatic appendicitis.
Keywords: Subhepatic appendicitis; the fishbone sign; hyperechoic omental cap; diagnostic strategy; 20/80 rule;
the Pareto principle
Submitted Jun 17, 2020. Accepted for publication Aug 25, 2020.
doi: 10.21037/atm-20-5265
View this article at: http://dx.doi.org/10.21037/atm-20-5265
Introduction
EAES and WSES guidelines recommended to make
a combination of “ultrasound” and “comprehensive
clinical indicators” to form a clinical-imaging score
could significantly improve the sensitivity and specificity
of appendicitis diagnosis, and reduce the need for CT
examinations in the diagnosis of acute appendicitis.
Although the clinical-imaging score could significantly
improve the accuracy and specificity of appendicitis
diagnosis, the diagnosis of appendicitis remained to be a
1083
Original Article
Yu et al. Ultrasound features of subhepatic appendicitis
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Page 2 of 11
challenge and the clinical management of appendicitis was
also in dispute (1). After review of the appendicitis surgery
data in our hospital from January 2014 to January 2018,
we found that the main reason for the missed diagnosis
of appendicitis was the abnormal location of the appendix
(the appendix located far away from the McBurney point).
Subhepatic appendicitis is a common type of variation in
the position of the appendix, with low morbidity and a high
rate of missed diagnosis (2). The common type of abnormal
appendicitis was subhepatic appendicitis. In this review and
analysis, the diagnostic accuracy of subhepatic appendicitis
in our hospital was only 11.1%. Due to the overhigh rate
of missed diagnosis, we focused on the ultrasound diagnosis
in subhepatic appendicitis. For open appendectomy
(OA), the accurate diagnosis of subhepatic appendicitis by
ultrasound and body surface positioning could help the
surgeon find the best surgical incision in the upper right
abdomen. For LA and SLA, the ultrasound could help the
surgeon select a more easy-to-operate “hole”. This was a
retrospective cohort study on the ultrasound features of
subhepatic appendicitis. Combining the “20/80 rule” and
“the Pareto principle”, this study made logical judgments
on the combination of direct ultrasonic images with
indirect ultrasonic images of subhepatic appendicitis and
explored the diagnostic strategy of subhepatic appendicitis
(3-5). The effective combination of statistical method and
logical judgment method was an exploration of a whole
new diagnostic mode in clinical study. The improvement
of accuracy in the diagnostic of subhepatic appendicitis by
ultrasound provided a basis for selection of surgical timing
and surgical methods.
We present the following article in accordance with the
STROBE reporting checklist (available at http://dx.doi.
org/10.21037/atm-20-5265).
Methods
Patients
All procedures performed in this study involving human
participants were in accordance with the Declaration of
Helsinki (as revised in 2013). This study was reviewed
and approved by the Ethics Committee of Jizhong Energy
Fengfeng Group Hospital and informed consent was
taken from all the patients. Totally 1,591 patients with
appendicitis who were treated at Jizhong Energy Fengfeng
Group Hospital between January 2014 and January
2018 were analyzed, and 20 patients with subhepatic
appendicitis, confirmed through an open appendectomy,
or laparoscopic appendectomy, was selected as the
population. Eighteen of the patients had complete clinical
data and preoperative US data.
Inclusion criteria: for the group of patients with
subhepatic appendicitis (Group A), cases with complete
clinical data and ultrasound data were screened. For the
group of patients with appendicitis with normal position
(Group B). Appendicitis cases with complete data were
numbered and entered in the SPSS 21.0 software, and then
25 cases were randomly selected (Figure 1).
Exclusion criteria for the study were: (I) patients without
undergoing ultrasound examination before surgery; (II)
patients with incomplete clinical data; (III) cases without
having been conrmed through surgery; (IV) patients who
are complicated by periappendiceal abscess and not t for
phase I surgical treatment; (V) Crohn’s disease; (VI) right-
sided diverticulitis; (VII) right-sided segmental omental
infarction; (VIII) appendiceal lesions with appendiceal
mucocele.
Classication: the ultrasound-positive ndings in Group
A and Group B were sorted and classied on the screening
results and clinical experience.
Equipment
Philips IU Elite Ultrasound System with L5–12 linear array
probes and C1–5 sector probes, Philips HD15 Ultrasound
System with L3–12 linear array probes and C1–5 sector
probes, and HITACHI EUB-8500 Ultrasound System with
13-6 linear array probes and 5-2 sector probes were used.
Ultrasound techniques
During the ultrasound examination, the patients were
instructed to lie in a supine position, with the abdomen
exposed and a suitable amount of ultrasound gel applied.
An abdominal ultrasound examination starts with the
right lower abdomen. All the radiologists were trained
on the standard operating procedure for acute abdominal
ultrasound diagnosis.
Variables for observation: (I) the fishbone sign: When
the jejunum dilates in the lower abdomen, the small
intestinal mucosa can be recognized, and jejunal villi can
be recognized, presenting with fishbone-like ultrasound
findings; (II) enlarged appendix: a vermiform structure in
the right lower or upper abdomen, with a lumen diameter
>6 mm and a wall thickness >2 mm (6,7); (III) the presence
Annals of Translational Medicine, Vol 8, No 17 September 2020 Page 3 of 11
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Appendicitis with
another position
n=59
Subhepatic
appendicitis had
uncomplete data
n=2
Fish bone
sign
n=16
Vermiform
structure
n=5
The total Ultrasound
features (n=30)
Subhepatic appendicitis
n=20
Subhepatic appendicitis
had complete data
Group A (n=18)
Appendicitis with
abnormal position
n=79
Appendicitis
n=1,591
Vermiform
structure
n=22
Appendicoliths
n=14
Hyperechoic
omental cap
n=13
Fish bone
sign
n=4
Lymphadenect
asis
n=7
The total Ultrasound
features (n=60)
Appendicitis with normal
position
n=1,512
Random sampng
Group B (n=25)
Appendicoliths
n=2
Hyperechoic
omental cap
n=4
Lymphadenect
asis
n=3
Figure 1 Flow diagram for the patients. Data are presented as the number of patients in each category.
of lymphadenectasis in the abdominal cavity, with the ratio
of the long axis-short axis <2 and the short axis >5 mm (8);
(IV) appendicoliths: calcied fecal deposits that are known
as appendicoliths, manifested as strong cloddy echoes with
sound shadows behind on the ultrasound imaging (9-13); (V)
hyperechoic omental cap: thickened oedematous omentum
surrounding the appendix (Figures 2-5).
General clinical data
General clinical data include patient age, sex, body
mass index (BMI), white blood cell (WBC), neutrophil
percentage, body temperature, with or without the irritative
symptoms of peritonitis, with or without signs of metastatic
lower abdominal pain, and course of the disease.
Pareto chart and the Pareto principle
The Pareto principle: factors with a cumulative distribution
of 0% to 80% were primary, factors with a cumulative
distribution of 80% to 90% secondary, and factors with a
cumulative distribution of 90% to 100% general (14).
Pareto chart: a bar chart was drawn with the ultrasound
findings of appendicitis as the X-coordinate and the
number of patients with distinct types of appendicitis on
the ultrasound imaging as the Y-coordinate. A broken line
chart was drawn with the ultrasound ndings of appendicitis
as the X-coordinate and the cumulative percentage as the
Y-coordinate. Afterward, the bar chart and the broken
line chart were integrated with the Y-coordinate as the
benchmark to form a Pareto chart.
Pathological classication of appendicitis
Pathological classification: (I) acute simple appendicitis;
(II) acute phlegmonous appendicitis; (III) acute gangrenous
appendicitis; and (IV) periappendiceal abscess (15,16). As
patients with periappendiceal abscess are not fit for phase
I surgical treatment, this type of patient is not included in
this study.
Statistical methods
SPSS21.0 software was used for statistical analysis.
Measurement variables were expressed in
sx ±
, and
the t-test was used for comparing the differences in the
Yu et al. Ultrasound features of subhepatic appendicitis
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Page 4 of 11
Figure 2 The clinical and US features of subhepatic appendicitis. (A) Subhepatic appendicitis in a 40-year-old man. The short axis shows
an enlarged appendix with the target shape (arrow); (B) Long axis showing an enlarged appendix with 9 mm outside diameter (arrows);
(C) Dilated small intestinal showing shbone sign in the right lower abdomen (arrows); (D) enlarged appendix sitting under the liver in
laparoscopic appendectomy; (E) specimen of the appendix here; (F) HE 4×10 Hemorrhage and necrosis in the appendix with neutrophil
inltration; (G) HE 10×10 Marked neutrophilic inltrate within tunica muscularis.
Figure 3 Subhepatic appendicitis in a 20-year-old, hyperechoic
omental cap (arrows). Figure 4 Appendicolithiasis in 25-year-old women (arrows).
B
D E F
CA
G
measured values between the two groups. A Chi-square test
was used for comparison of count variables between the
two groups. The Contingency Table was used for ordered
categorical variables. Spearman’s rank correlation was
used for testing on the correlation of ranked variables, and
P<0.05 showed a statistical difference. Remove cases with
incomplete data. The quality management tools of this
study are the Pareto chart and the Pareto principle. The
Pareto chart was drawn to nd the main diagnostic factors
according to the Pareto principle.
Results
Comparison of general clinical data
Group A: sex (male/female): 11/7; age (42.77±16.34);
BMI (23.78±4.89), WBC (14.39±2.01)×109; neutrophils %
(76.74±4.03); body temperature (8.28±0.60) ℃; irritative
symptoms of peritonitis (+/−): 16/2; and duration from onset
to surgery (7.33±1.78) days. The total of 30 accumulated
ultrasound manifestations.
Group B: sex (male/female): 16/9; age (30.64±15.27);
Annals of Translational Medicine, Vol 8, No 17 September 2020 Page 5 of 11
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
BMI (24.32±3.88); WBC (13.01±2.71)×109; neutrophils %
(74.49±3.32); body temperature (38.41±0.57) ℃; irritative
symptoms of peritonitis (+/−): 25/1; and duration from onset
to surgery (4.16±1.49) days. The total of 60 accumulated
ultrasound manifestations.
P was greater than 0.05 for comparison between the two
groups, showing that there were no statistically signicant
differences in the clinical data of the patients between the
two groups (Table 1).
Comparison of ultrasound ndings between Group A and
Group B
Comparisons between the two groups showed an χ2=28.135
with a P value <0.05 for the fishbone sign of dilated
ileum in the right lower abdomen, an χ2=16.245 with
a P<0.05 for vermiform structure, an χ2=9.026 with a
P<0.05 for appendicoliths, and an χ2=3.882 with a P<0.05
for hyperechoic omental cap, with statistical significance
observed with differences in frequencies of the samples
between the two groups. For whether there was a presence
of lymphadenectasis, the comparison showed an χ2=0.753
with a P value of 0.386 greater than 0.05, indicating the
difference in the frequency between the two groups was not
statistically signicant (Table 2).
The observed variables of statistical significance are
screened out and ranked by the positive rate from highest to
lowest as follows:
In Group A: the fishbone sign in the right lower
abdomen (88.9%) > vermiform structure (27.8%) in the
right upper abdomen > hyperechoic omental cap (22.2%) >
appendicoliths (11.1%).
In Group B: vermiform structure in the right lower
abdomen (92.0%) > appendicoliths (56.0%) > hyperechoic
omental cap (52.0%) > dilated intestine in the right lower
abdomen (16.0%).
Appendicitis with normal position and subhepatic
appendicitis is divided into A, B, C and D types for
the two groups on the sequences of abnormal positive
ndings screened out using Chi-square test and on clinical
experience
In Group A: Type A: the fishbone sign in the right lower
abdomen; Type B: the fishbone sign in the right lower
abdomen + vermiform structure in the right upper
abdomen; Type C: the fishbone sign in the right lower
abdomen + vermiform structure in the right upper abdomen
+ hyperechoic omental cap; and Type D: the fishbone
sign in the right lower abdomen + vermiform structure
in the right upper abdomen + hyperechoic omental cap +
appendicoliths.
Figure 5 Regular posed appendicitis with panoramic ultrasound
imaging in a 19-year-old woman.
Table 1 Comparison of general clinical data between Group A and Group B
Variable Group A (n=18) Group B (n=25) F/χ2P
Sex (male/female) 11/7 16/9 0.037 0.847
Age (years) 42.77±16.34 30.64±15.27 0.156 0.695
BMI 23.78±4.89 24.32±3.88 1.220 0.276
WBC (×109) 14.39±2.01 13.01±2.71 1.410 0.242
Neutrophils % 76.74±4.03 74.49±3.32 1.834 0.183
Body temperature (℃) 38.28±0.60 38.41±0.57 0.276 0.602
Irritative symptom (+/−) 16/2 25/1 0.088a0.767
Duration from onset to surgery 7.33±1.78 4.16±1.49 2.282 0.139
a, continuity correction.
Yu et al. Ultrasound features of subhepatic appendicitis
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Page 6 of 11
Table 3 Association analysis of Group A and Group B
Group Type A Type B Type C Type D Mean rank P
Group A 11 2 2 1 35.389 0.315
Group B 11 8 2 2 41.41
Table 2 Comparison of ultrasound ndings between Group A and Group B (%)
Variables of ultrasound characteristics Group A (n=18) Group B (n=25) χ2P
The fishbone sign 22.348 0.000
+ 16 (88.9) 4 (16.0)
− 2 (11.1) 21 (84.0)
Enlarge appendix 19.002 0.000
+ 5 (27.8) 23 (92.0)
− 13 (72.2) 2 (8.0)
Lymphadenectasis 0.252a0.616
+ 3 (16.7) 7 (28.0)
− 15 (83.3) 18 (72.0)
Appendicoliths 9.026 0.03
+ 2 (11.1) 14 (56.0)
− 16 (88.9) 11 (44.0)
Hyperechoic omental cap 3.882 0.049
+ 4 (22.2) 13 (52.0)
− 14 (77.8) 12 (48.0)
a, continuity correction.
In Group B: Type A: vermiform structure in the right
lower abdomen; Type B: vermiform structure in the right
lower abdomen + appendicoliths; Type C: vermiform
structure in the right lower abdomen + appendicoliths
+ hyperechoic omental cap; and Type D: vermiform
structure in the right lower abdomen + appendicoliths +
hyperechoic omental cap + the shbone sign in the right
lower abdomen.
Analysis using the contingency table for the ultrasonic
classification: the mean rank was 41.41 for Group B and
35.389 for Group A, with a P value of 0.315, supporting
the original hypothesis that the classification using the
diagnostic strategy for Group A was consistent to that for
Group B (Table 3).
Analysis of correlation between ultrasonic classification
and pathological classification: in Group B, ultrasonic
classification is positively correlated with pathological
classification, with a Spearman’s correlation coefficient of
0.716. In Group A, ultrasonic classification is positively
correlated with pathological classication, with a Spearman’s
correlation coefcient of 0.747 (Table 4).
Pareto chart and the Pareto principle
Group A: Type A and Type B were the main ultrasound
ndings, with a cumulative percentage of 81.25%. Type A:
the shbone sign of the dilated small intestine in the right
lower abdomen; Type B: the fishbone of the dilated small
intestine in the right lower abdomen + vermiform structure
in the right upper abdomen (Table 5; Figure 6).
Group B: Type A and Type B were the main ultrasound
ndings, with a cumulative percentage of 82.61%. Type A:
vermiform structure in the right lower abdomen; Type B:
vermiform structure + appendicoliths (Table 5; Figure 7).
Annals of Translational Medicine, Vol 8, No 17 September 2020 Page 7 of 11
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Table 5 The analysis of the ultrasound categorization of Group A and Group B
Categorization
Group A Group B
n Constituent ratio (%) Cumulative percentiles (%) n Constituent ratio (%) Cumulative percentiles (%)
Type A 11 68.75 68.75 11 47.83 47.83
Type B 2 12.50 81.25 8 34.78 82.61
Type C 2 12.50 93.75 2 8.70 91.30
Type D 1 6.25 100.00 2 8.70 100.00
Table 4 The association analysis on the ultrasound categorization and the pathological classication about subhepatic appendicitis
Group Type A Type B Type C Type D r (P)a
Group A 0.747
Acute simple appendicitis 8 – – –
Acute phlegmonous appendicitis 2 2 – –
Acute gangrenous appendicitis 1 – 2 1
Total 11 2 2 1
Group B 0.716
Acute simple appendicitis 9 1 – –
Acute phlegmonous appendicitis 1 6 1 –
Acute gangrenous appendicitis 1 1 1 2
Total 11 8 2 2
a, Spearman correlation test.
16
14
12
10
8
6
4
2
0
100.00%
80.00%
60.00%
40.00%
20.00%
0.00%
Group A
n
Cumulative
percentiles (%)
Type A Type B Type C Type D
Figure 6 Group A: Type A and Type B were the main ultrasound
ndings, with a cumulative percentage of 81.25%.
20
15
10
5
0
100.00%
80.00%
60.00%
40.00%
20.00%
0.00%
Group B
n
Cumulative
percentiles (%)
Type A Type B Type C Type D
Figure 7 Group B: Type A and Type B were the main ultrasound
ndings, with a cumulative percentage of 82.61%.
Discussion
Appendicitis is the most common surgical abdominal
emergency in the developed world and developing world
(17-21). Although anatomic variations are less common,
most of the surprises encountered during an appendectomy
are usually due to the various positions of the appendix. It is
of great signicance for surgeons and ultrasonographers to
gain a full understanding of the appendix with an abnormal
Yu et al. Ultrasound features of subhepatic appendicitis
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Page 8 of 11
position (22-24).
Subhepatic appendicitis, also called appendicitis with a
high position, refers to the inflamed appendix above the
navel and is the most common type of appendicitis with the
abnormal position (25-27) (Figure 2D). The development
of the appendix is closely related to the development of the
midgut. The primitive gut begins to develop at four weeks
of gestation and can be divided into the foregut, midgut, and
hindgut by the end of the fifth week. The first structures
of the caecum and appendix become visible as bud of the
caecum The appendix becomes visible in the eighth week
of gestation. Colon stretching and elongation results in the
descent of the caecum and vermiform appendix, pushing
the appendix ahead of the caecum. In the postpartum
period, the appendix and the caecum descend to the normal
position. Subhepatic appendicitis primarily results from
midgut malrotation, non-descent of the caecum, or is a
result of free caecum (28-30).
Dilated jejunum is due to the widening of the jejunum
and deposition of intestinal contents, with the intestinal
mucosa displayed clearly against the background of the
intestinal contents. It is primarily manifested as the
fishbone sign on the ultrasound imaging (Figure 2C). It
has a low display rate of only 8% in appendicitis with
the normal position, but a display rate of up to 88.9% in
subhepatic appendicitis. These results could be attributed
to the following: (I) variation in the anatomic position:
in subhepatic appendicitis, the colon moves up, and the
jejunum rotates and aggregates in the right lower abdomen.
The display rate of the ileum is high; (II) inflammatory
stimulation: the inflammatory exudates of subhepatic
appendicitis flow in the direction of gravity into the right
lower abdomen, and paralysis is caused to the ileum due to
inammatory stimulation from the exudates, consequently
resulting in reduced peristalsis and deposition of intestinal
contents; (III) display of the small intestinal mucosa: the
dilated small intestine can be displayed on the ultrasound
imaging. The above factors lead to a high positive rate of
the shbone sign in the right lower abdomen in subhepatic
appendicitis. The shbone sign is also the main lead in the
ultrasonic diagnosis of subhepatic appendicitis.
The vermiform structure is direct evidence for a
diagnosis of appendicitis (Figure 5). When performed by
ultrasonographers properly trained on acute abdominal
ultrasound, appendicitis with the standard position was
displayed by up to 90%. This figure shows the advantage
of ultrasound in the diagnosis of appendicitis in a
normal position. While in Group A, the display rate was
only 27.8%. This difference could be attributed to the
following: (I) the physician performing the examination
was not familiar with subhepatic appendicitis, resulting in
a decreased detection rate of subhepatic appendicitis; (II)
signicant anatomic variation exists with an appendix with
a high position, for it can appear at any position in the
abdominal cavity. The uncertainty of the anatomic position
has increased the difficulty in locating the appendix; (III)
the appendix with the high position is mostly located in
posterior colon/jejunum, and gas present in the colon
interferes with the display of the appendix.
Appendicoliths is the leading cause responsible for
the acute onset of appendicitis (31-35) (Figure 4). In
appendicitis with normal position (Group B), the display
rate of appendicoliths could be up to 56% due to a fixed
position of the appendix. While in subhepatic appendicitis
(Group A), the display rate of appendicoliths was low due to
the different anatomic position and impact of surrounding
tissues. It was only 11.1%.
Hyperechoic omental cap is a manifestation of extra-
intestinal fat inflammation. Accumulation of purulence
in the appendiceal cavity increases pressure in the cavity,
and the involvement of fats surrounding the appendix by
inflammation leads to lipedema, with fats encapsulating
around the appendix. The occurrence of a hyperechoic
omental cap indicates the worsening of appendicitis. The
display rate of the hyperechoic omental cap was 52.0% in
Group B, and 22.2% in Group A. Hyperechoic omental cap
helps localize inammation. Subhepatic appendicitis is often
complicated by an abnormal distribution of fats around the
appendix, with incomplete fat encapsulation (Figure 3).
After a statistical comparison, the observed variable
lymphadenectasis in the abdominal cavity was not included
as a subject of this study, and it fulfills the diagnostic
thinking. Appendiceal inammation is not an independent
correlation factor for lymphadenectasis. (I) Age is a
confounding factor for the display of lymphadenectasis,
which has a varying rate of display in different age groups,
with a higher rate in the infants than in the adults. (II)
Multiple abdominal disorders can lead to lymphadenectasis,
including inflammatory bowel disease, gastrointestinal
tumor, mesenteric lymphadenitis. The Pareto principle is
also known as the 80/20 rule, the law of the vital few, or
the principle of factor sparsity (36,37). The Pareto chart is
a bar chart of frequencies sorted by frequency. The most
commonly used incarnation of the chart puts the highest
bars on the left and includes a line showing the scores
produced by adding the heights in order from left to right.
Annals of Translational Medicine, Vol 8, No 17 September 2020 Page 9 of 11
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
This chart is used widely in quality control settings to nd
critical factors leading to failure or defects in a process. The
Pareto chart principle is widely applied in the management,
and applying this principle can show the leading factors
of the problem efficiently and objectively. We applied
this principle in finding the leading factors for ultrasonic
findings of subhepatic appendicitis in this study, which
was a combination of statistics and management. This
principle was used to summarize the diagnosis of subhepatic
appendicitis: only 20% of ultrasound-positive features
were presented in 80% of the patients with subhepatic
appendicitis (38-42).
In subhepatic appendicitis (Group A), the main types of
ultrasound ndings are (I) dilated ileum in the right lower
abdomen, and (II) dilated ileum in the right lower abdomen
+ vermiform structure in the right upper abdomen. Dilated
ileum in the right lower abdomen is the main, leading
to the diagnosis of subhepatic appendicitis. In the case
of clinical data of suspicious appendicitis, the surgeon
and the ultrasonographer should consider the possibility
of subhepatic appendicitis and perform a careful scan
examining whether there are echoes of vermiform structure
in the right upper abdomen when dilated ileum is seen in
the right lower abdomen, to avoid a missed diagnosis of
subhepatic appendicitis.
In appendicitis with normal position (Group B), the main
types of ultrasound findings are as follows: (I) vermiform
structure in the right lower abdomen; and (II) vermiform
structure in the right lower abdomen + appendicoliths
observed in the vermiform structure. Dilated ileum in the
right lower abdomen was a general factor in appendicitis with
a normal position. In other words, the possibility of dilated
ileum occurring in appendicitis with the normal position is
low. It may only exist in cases of serious exudation from the
appendix causing small intestinal paralysis.
Currently, laparoscopic appendectomy (LA) was the
main treatment for acute appendicitis. Mini-incision
open appendectomy (MOA), single port laparoscopic
appendectomy (sLA) and (Natural orifice transluminal
endoscopic surgery (NOTES) via various methods were
also the treatments. The treatments for normal appendicitis
and subhepatic appendicitis were basically in consistency,
for which the surgical excision was recommended. However,
the positions of surgical incisions between the two were
different. For normal appendicitis, generally appendectomy
was conducted at the McBurney point in the right lower
abdomen. For subhepatic appendicitis, the best surgical
approach needed to be in the near location after positioning
of body surface by ultrasound. When selecting LA, for
subhepatic appendicitis, the body surface projection was
needed to be labelled under the guidance of ultrasound.
The surgeon selected the best position of the puncture hole
for the laparoscope according to the projection position
of body surface. The diagnosis of subhepatic appendicitis
could improve the cure rate, select the most suitable surgical
approach, shorten the operation time, and ensure patient’s
safety to the greatest extent.
When it is suspected to be subhepatic appendicitis
through “comprehensive clinical indicators”, each ultrasound
feature is of great signicance to the diagnosis of subhepatic
appendicitis. The more cumulative positive ultrasound
features, the higher the diagnostic accuracy. Combined
with the 20/80 rule, when comprehensive clinical indicators
support appendicitis with fishbone sign been found by
ultrasound scan of the right lower abdomen, the ultrasound
physician shall consider whether it is subhepatic appendicitis.
At this time, the upper right abdomen needs to be carefully
scanned for evidence of subhepatic appendicitis by the
examiner. The purpose of study on ultrasound features of
subhepatic appendicitis is to improve the diagnosis accuracy
of subhepatic appendicitis and allow patients with subhepatic
appendicitis to receive timely treatment.
Conclusions
This study has summarized the ultrasonic diagnostic
procedure for subhepatic appendicitis. This procedure
can achieve a similar diagnostic effect as the procedure for
appendicitis with a normal position. The presence of an
abnormally dilated ileum in the right lower abdomen − the
shbone sign, is the rst lead to the diagnosis of subhepatic
appendicitis.
A specialized diagnostic strategy for subhepatic
appendicitis for patients with clinically suspicious
appendicitis when a vermiform structure is not scanned
in the right lower abdomen and only dilated ileum (the
fishbone sign) should be utilized. A scan focusing on
determining whether there is a presence of vermiform
structure in the right upper abdomen should be performed,
and the possibility of subhepatic appendicitis should not be
ruled out even if the presence of the appendix with the high
position is discovered.
Acknowledgments
Funding: None.
Yu et al. Ultrasound features of subhepatic appendicitis
© Annals of Translational Medicine. All rights reserved. Ann Transl Med 2020;8(17):1083 | http://dx.doi.org/10.21037/atm-20-5265
Page 10 of 11
Footnote
Reporting Checklist: The authors have completed the
STROBE reporting checklist. Available at http://dx.doi.
org/10.21037/atm-20-5265
Data Sharing Statement: Available at http://dx.doi.
org/10.21037/atm-20-5265
Conicts of Interest: All authors have completed the ICMJE
uniform disclosure form (available at http://dx.doi.
org/10.21037/atm-20-5265). The authors have no conicts
of interest to declare.
Ethical Statement: The authors are accountable for all
aspects of the work in ensuring that questions related
to the accuracy or integrity of any part of the work are
appropriately investigated and resolved. All procedures
performed in this study involving human participants were
in accordance with the Declaration of Helsinki (as revised in
2013). This study was reviewed and approved by the Ethics
Committee of Jizhong Energy Fengfeng Group Hospital
and informed consent was taken from all the patients.
Open Access Statement: This is an Open Access article
distributed in accordance with the Creative Commons
Attribution-NonCommercial-NoDerivs 4.0 International
License (CC BY-NC-ND 4.0), which permits the non-
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the strict proviso that no changes or edits are made and the
original work is properly cited (including links to both the
formal publication through the relevant DOI and the license).
See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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(English Language Editor: J. Chapnick)
Cite this article as: Yu D, Gu C, Zhang S, Yang H, Yao T.
Ultrasound features and the diagnostic strategy of subhepatic
appendicitis. Ann Transl Med 2020;8(17):1083. doi: 10.21037/
atm-20-5265