TITLE: A PROSPECTIVE CROSS-SECTIONAL STUDY OF THE SENSITIVITY OFULTRASOUND IN THE DIAGNOSIS OF ACUTE APPENDICITIS
ARTICLE TYPE: ORIGINAL ARTICLE / RESEARCH
SECTION/CATEGORY: EMERGENCY ULTRASOUND
AUTHORS:
:1. ADETUNJI S OGUNTOLA, MBBS, FWACS; DEPT OF SURGERY, LAUTECH OGBOMOSO NIGERIA
2. TEMITOPE O BELLO,MBBS, FWACS; DEPT OF RADIOLOGY, LAUTECH OGBOMOSO NIGERIA
3. JEHAD ALAKABANI. MBBS, MSC DEPT OF RADIOLOGY, ALHAWRA GENERAL HOSPITAL, UMMLUJ, TABUK REGION KINDOM OF SAUDI ARABIA.
CORRESPONDING AUTHOR: DR. TEMITOPE O BELLO, MBBS, FWACS
RADIOLOGY DEPT., LADOKE AKINTOLA UNIVERSITY. NIGERIA
ABSTRACT:
INTRODUCTION: - Diagnosis of appendicitis is mainly clinical
but usually supported with laboratory and radiological diagnosis
especially ultrasonography. There has been conflicting report on the role
of ultrasound in the management of appendicitis. Our objective is to
assess the sensitivity of ultrasound in the diagnosis of appendicitis.
METHODS:-forty three patients with clinicaly diagnosed acute appendicitis
were involved in this study. Emergency Pelvic ultrasonography was done on
the patients to assess the appendix; all the patients had open
appendectomy. Criteria considered for ultrasound diagnosis of
appendicitis include non-compressible appendix and maximal outer diameter
(MOD) greater than 6 mm, edema of the appendix, presence of faecolith,
peri-appendiceal fluid collection and mesenteric lymphadenopathy.
The intraoperative findings were compared to the ultrasound assessment.
Also, the removed appendices were sent for histology. The sensitivity of
ultrasound in the diagnosis of appendicitis was estimated, and the
histology results were used as the gold standard. Data for age, sex,
clinical diagnosis, intra-operative findings, ultrasound results,and
histological results were collected and analysis performed using SPSS
version 15 ( Illinois, Chicago, USA). P-values less than 0.05 were
accepted as significant.
RESULTS; forty three patients were seen during the study period, the mean
age was 21.9 ±9.51yrs. Ultrasound correctly diagnosed appendicitis
in 24 patients. The ultrasonography signs were edema of the appendix in
24 patients, presence of faecolith in 6 patients and periappendiceal
fluid in 8 patients, one patient demonstrated appendiceal mass. The MOD
of the appendix ranges from 6 to 17 mm (mean 9.91mm ±3.21) and 37% of
appendix with MOD above 10mm had appendicitis.
True positive on Ultrasound is 24 , and false negative is 18. The
sensitivity rate is 57 %.
CONCLUSSION: - Ultrasound is a good adjunct in the clinical diagnosis of
equivocal appendicitis
Keywords: pelvic ultrasonography, acute appendicitis, emergency
ultrasound
Title: A prospective cross-sectional study of the sensitivity of ultrasound in the diagnosis of
acute appendicitis
INTRODUCTION
Acute appendicitis is the commonest acute surgical condition in the developed world with
mortality of about 1%1, 2. It is also the most common surgical condition in the third world,
and the cost of investigation and prompt therapy may be out of reach of the patients resulting
in higher mortality.3 It has also been established that acute abdominal pain is a common
presentation of children seeking medical care. Suspected acute appendicitis is the most
common condition requiring abdominal surgery in the paediatric population and must be
differentiated from other conditions that may mimic its signs.4 Occasionally, clinical
presentations may be confusing, especially in children and older patients. A history of
abdominal pain, classically beginning in the periumbilical region and migrating to
McBurney’s point, combined with leucocytosis and other associated symptoms such as
anorexia remains the best diagnostic clue.5
Diagnosis of appendicitis is mainly clinical but usually supported with laboratory and
radiological diagnosis. The frequency of unnecessary appendectomy has been estimated to be
between 10 and 30%. This implies that there is a need for accurate preoperative assessment;
imaging by ultrasound or computerized axial scan to assess the state of the appendix is
important to reduce unnecessary appendectomy However, ultrasonography offers the
advantage of affordability, ionizing radiation free, and portability, therefore it is usually the
first imaging test in the evaluation of patients with suspected appendicitis6.
This reports summarized the sensitivity of ultrasonography in the diagnosis of acute
appendicitis.
METHODOLOGY
This a prospective cross sectional study of patients with suspected acute appendicitis at the
Al-Hawra General Hospital, in the Tabuk Region of the kingdom of Saudi-Arabia over a 20-
month period spanning from August 2009 to March 2011. Patients with suspected
appendicitis were evaluated by the General Surgeon and referred for ultrasonography.
The Radiologist performed a graded compression ultrasonography with a LOGIC 400 (GE
,Phillips, USA), ultrasound machine using a 8 - 14 MHZ linear probe. Criteria for the
diagnosis of appendicitis included non-compressible appendix and measured maximal outer
diameter of greater than 6 mm, edema of the appendix, presence of faecolith, periappendiceal
fluid collection and mesenteric lymphadenopathy. The ultrasound results were
classified as confirmed appendicitis or normal .
Open appendicectomy under general anesthesia were done for all the patients. The
appearance and thickness of the appendix, presence of peri-appendicial fluids and pus were
documented. Furthermore, the specimen was sent for histologic diagnosis..
The data for age, sex, , intra-operative findings, ultrasound results, and histological results
wereanalysed using SPSS for Windows (version 15·0). P-values less than 0.05 were accepted
as significant.
RESULTS
Ninety five patients had a clinical diagnosis of appendicitis during the period of study, but
only 43 patients, who had graded ultrasound, appendectomy and histology results were
involved in the study. The Forty three patients involved in this study comprise 32 males and
11 females, the ages ranged from 5 to 44years ( mean age 21.9 ±9.51) . The mean for the
males is 23.7 years and 20.09 yrs for females.
The reference standard for the diagnosis of appendicitis was histology. Forty two out of the
43 patients were diagnosed as appendicitis on histology, out of which ultrasound correctly
diagnosed 24 true positive, 18 False negative. The true positive rate of ultrasonography is
57.14%.
The US findings included oedema of the appendix in 24(57.1%), presence of faecolith in 6
patients, and peri-appendiceal fluid in 8 patients and appendiceal mass in one patient. (Table
1 and figure 1)
FIGURE 1: Ultrasound demonstrated marked thickening of the appendix (red arrow) and
peri-appendiceal fluid collection (white arrow
The maximal outer diameter of the appendix on ultrasound ranges from 6 to 17 mm ( mean
9.91mm ±3.21). Fifteen percent of patients with diameter of the appendix below 10mm had
appendicitis, as compared to 37% of patients with appendix diameter greater than 10m,
though finding was not statistically significant (p value =0.248) (Table 1)
TABLE 1
ULTRASOUND FEATURES OF APPENDICITIS
Ultrasound findings N 42(%)
Normal 18 (42.9)
Edema 24(57.1)
Faecoliths 6(14.3)
Peri-appendicial fluid 8(19.0)
Appendiceal mass 1(2.4)
Appendiceal diameter < 6 mm
6 - 10 mm
≥10 mm
3(7.1)
13(31.0)
8 (19.0)
. In this study, ultrasound categorized all the cases of reactive lymphoid hyperplasis as
normal, this is responsible for the high false negative rate on ultrasound. However all cases of
perforated ruptured appendix were diagnosed correctly (Table 2)
.
Table 2
Ultrasound diagnosis compared with the histology report
a TP =24, FN=19, Sensitivity= 57.14%
HISTOLOGICAL DIAGNOSIS N
Normal Acute
appendicitis
Ruptured/per
forated
Reactive
lymphoid
hyperplasia
Chronic
appendicitis
Ultrasound
diagnosis
Positive 0 19 5 0 0 24
Negative 1 11 0 6 1 19
Total 1 30 5 6 1 43
Discussion
Ultrasonography features of acute appendicitis includes non compressible appendix without
peristaltic movement, thickened appendiceal wall more than 6mm,increased echogenicity of
theperi-appendiceal fat, presence of appendicoliths and appendiceal mass. There are many
disease states that can present similar to acute appendicitis such as Urolithiasis, salpingitis,
torsion of ovarian cyst. Acute appenicities has a wide range of presentations , and therefore,
there is need for accurate diagnosis prior to surgery.
The most widely used modalities are CT scan, Ultrasonography and Laparascopy.
Ultrasonography offers certain advantages over CT and laparascopy, it is more available,
non-invasive, portable, and affordable. These advantages are of great value in Africa, in
some parts of the continent the modest ultrasound machine may be the only available tool to
assist the surgeon to make pre-operative diagnosis. A major limitation is its use in obese
individuals and it is highly user-dependent.6,7 . The presence of gas in the abdomen and
unusual location of appendix may limit its sensitivity and specificity.8 However cost
analyses research confirmed that pelvic ultrasound for suspected appendicitis was justified
and appropriate 8,9
Diagnosis of acute appendicitis may sometimes be quite challenging, atypical presentation
may pose a dilemma even for an experienced surgeon. The confusion can result in the
removal of a normal appendix or delaying the removal of a diseased appendix.10It has been
recorded that misdiagnosis of acute appendicitis is a common and crucial problem in general
surgery. The conventional surgical wisdom is to operate when in doubt, this has led to 20-
30% increase in the negative appendicectomy, which is considered unacceptable.11To
overcome the problem of missed diagnosis , a clinical scoring system has been adopted
[Alvarado], which consist of 2 laboratory tests and 6 clinical assessments.
A major limitation of our study design is that all the patients had symptoms that were highly
suspicious of acute appendicitis, 42 out of the 43 patients were confirmed to have
appendicitis on histology. The study is designed to assess the sensitivity of ultrasonography
in the diagnosis of patients with acute appendicitis, rather than specificity of ultrasound. In
this series, only one patient was wrongly diagnosed clinically as acute appendicitis; this
patient however was correctly diagnosed on ultrasound as true negative.
However, a major advantage of this study is its ability to assess the sensitivity of
ultrasonography in the detection of appendicitis. In this study, a factor responsible for the
high false negative rate was the percentage of patients in whom the histological diagnosis was
reactive lymphoid hyperplasis. In this group of patients, the core signs of appendicitis, such
as enlarged appendix or appendicoliths were absent. Therefore, in this group of patients, the
clinical assessment was more accurate than ultrasonography. Also, ultrasound was able to
correctly diagnosed only 57% of acute appendicitis in this study
Hung Ho et al, on his study from 766 consecutive patients with suspected acute appendicitis;
noted that Ultrasound was only accurate in 43.4%, CT Scan in 74.5% and Surgeon clinical
examination in 74.9%, from these he concluded that neither CT nor US improves the
diagnostic accuracy rate. In fact, Hung et al are of the opinion that ultrasonography may
delay surgical consultation and appendectomy.
In another series, by Mohammed et, they conclude that proper clinical assessment is the
mainstay of diagnosis in acute appendicitis and addition of routine ultrasound by graded
compression technique can improve the diagnostic accuracy and may reduce adverse
outcome.12 In this study, patients were divided into 2 groups; group 1 was managed with
ultrasonography and group 2 without ultrasonography. It was observed that sensitivity was
higher in group 1 while Specificity was higher in group 2. Rate of negative appendicectomy
was 22.5% in group 1 and 4.7% in group 2.
The observations of these authors are similar to our conclusion, that ultrasonography does
have some advantages as an adjunct to the diagnosis of acute appendicitis, but imaging
studies cannot replace the clinical judgment of experienced surgeons. Another important
additional advantage of ultrasound in acute appendicitis is the diagnoses of alternative
conditions in abdomen mimicking acute appendicitis.13
Furthermore, Jahn H.et al is of the opinion that clinical judgment of junior surgeons were
disappointing and diagnostic aids are desirable to reduce negative appendicectomy rate.14
Also, Sonography has a higher negative predictive value and should be considered as a
reasonable screening tool in the evaluation of acute appendicitis..15
In conclusion, graded compression ultrasonography for suspected cases of acute or subacute
appendicitis contributes significantly to the management of patients, and the procedure
should be encourage and the skills developed in developing countries to reduce negative
appendectomy, and improve the morbidity associated with appendicitis.
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