Al-Azhar Assiut Medical Journal

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 16  |  Issue : 1  |  Page : 21--26

A retrospective comparative study to evaluate the accuracy of ultrasound and multidetector abdominal computed tomography in the diagnosis of acute appendicitis


Abdel N Ghareep1, Lamya A Bekhet1, Ola I Saleh1, Rashad Al-Fkey2,  
1 Department of Radiodiagnosis, Faculty of Medicine, Al-Azhar University, Cairo, Egypt
2 Department of General Surgery, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

Correspondence Address:
Ola I Saleh
Department of Radiodiagnosis, Faculty of Medicine, Al Azhar University, Cairo, 11728
Egypt

Abstract

Objectives The aim of this study was to compare the diagnostic accurateness of ultrasound (US) with that of multidetector computed tomography (MDCT) for the diagnosis of appendicitis in patients with doubted acute appendicitis (AA). Patients and methods A retrospective study was carried out on 110 patients of all age groups in the period between November 2014 and January 2016. All patients presented to the emergency department in our institute with suspected diagnosis of AA using sonography and MDCT. Results US diagnosed correctly AA in 70/75 (93.3%) cases confirmed on histopathology. Computed tomography diagnosed correctly AA in 74/75 (98.6%) cases that confirmed on operation and by histopathology. Conclusion MDCT has mild superiority to US in the diagnosis of AA; however, US with expert hands and newer US machines have high sensitivity and specificity in the diagnosis, and without the hazards of radiation.



How to cite this article:
Ghareep AN, Bekhet LA, Saleh OI, Al-Fkey R. A retrospective comparative study to evaluate the accuracy of ultrasound and multidetector abdominal computed tomography in the diagnosis of acute appendicitis.Al-Azhar Assiut Med J 2018;16:21-26


How to cite this URL:
Ghareep AN, Bekhet LA, Saleh OI, Al-Fkey R. A retrospective comparative study to evaluate the accuracy of ultrasound and multidetector abdominal computed tomography in the diagnosis of acute appendicitis. Al-Azhar Assiut Med J [serial online] 2018 [cited 2020 Jul 6 ];16:21-26
Available from: http://www.azmj.eg.net/text.asp?2018/16/1/21/244151


Full Text



 Introduction



Acute appendicitis is the most common cause of acute abdominal pain requiring urgent surgery. A typical presentation results in difficulty in the clinical diagnosis. A wide spectrum of conditions can cause acute abdomen [1]. The possibility of perforation in children with acute appendicitis (AA) is high and happens in 23–73% of cases [2]. Generally, the normal appendix is not seen on ultrasound (US); however, other investigators have reported seeing even normal appendices on US in 5–50% of patients [3]. Before the appearance of modern techniques in diagnostic imaging, the diagnosis of AA was exclusively done clinically, and the need for imaging was to reduce the rate of perforated appendicitis and negative findings as much as possible [4].

The graded compression US technique styled by Puylaert et al. [5] has been verified to be valuable in the assessment of doubted AA and is now achieved routinely for most of the cases in our hospitals. Several studies have shown the negative appendectomy rate to decrease from more than 20% to less than 9% with the use of imaging [4],[6],[7]. Computed tomography (CT) is freely obtainable, nonoperator dependent, relatively easy to do, and has outcomes that are easy to interpret, but radiation hazards have to be kept in mind in younger age groups and considered the second choice when necessary [7].

 Patients and methods



Our institutional review board approved this retrospective study in accordance with the Helsinki Declaration. A study was carried on 100 patients of all age groups in the period between November 2014 and January 2016. All patients presented to the emergency department in our institute with suspected diagnosis of AA using sonography (My Lab50; Esaote) and multidetector computed tomography (MDCT) (Siemens-Somatom Sensation 64-slice, Siemens, Munich, Germany, and Toshiba Aquilion prime 164). Exclusion criteria were claustrophobia for imaging studies, patients cannot receive intravenous contrast, pregnant patients, Alvarado score less than 5, and fear of surgery. Of the admitted 110 patients with clinical suspicion of AA, 100 were examined with both US and MDCT, as five patients had Alvarado score 9–10 and needed to undergo urgent surgery (two of them were pregnant) and five patients left the hospital because of fear of surgery and were therefore excluded from imaging. Twenty-five patients after imaging were not operated as they were diagnosed to have diseases of other organs. In the rest of the 75 cases, surgery was done after imaging. An informed written consent was obtained from each patient or from patient’s relative. All patients were evaluated by the surgical team before diagnostic workup. Each patient was assigned a score using the Alvarado scoring system [8]. CT and US results were correlated with surgical and histopathologic outcomes.

For US, we used 12-MHz linear array transducer using the graded-compression technique with posterior manual compression of the right iliac fossa. We further asked the patient to pinpoint the area of maximum pain with his index finger and then starting US examination from all over the abdomen. The key feature to launch the diagnosis of AA on US remained direct visualization of the thickened inflamed appendix: a concentrically hypoechoic incompressible ([Figure 1]) blinded end tube-like structure (banana sign) on longitudinal scan and giving ‘Target’ appearance on transverse scan with a diameter of more than 7 mm ([Figure 2] and [Figure 3]) with moderately thickened wall of more than 3.5 mm establish at the area of maximum tenderness, with expanded lumen and echogenic inflamed surrounding fat with or without an appendicolith ([Figure 4] and [Figure 5]). The diagnostic criteria for negative findings on US are normal sized appendix (if visualized) with no tenderness in right iliac fossa.{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}

CT scans were done with multidetector CT machine by means of a rapid thin-scanning technique. Nonenhanced CT images were done first followed by contrast-enhanced scans performed after oral administration of 30 ml of Gastrografin diluted in 1 l of water. Rectal contrast was also ordered in some limited cases. The patients received a 125-ml intravenous bolus of contrast media (Omnipaque 300 mg/ml or Visipaque 320 mg/ml); a single breath-hold scan from diaphragmatic cupola to the symphysis pubis was obtained using 5-mm beam collimation and 5-mm/s table speed. The images were reconstructed at 1.5-mm intervals by different soft-tissue windows in multiplanar coronal and sagittal reformats.

In the current study, CT findings were considered as positive for AA when dilated thickened appendix of more than 6 mm in outer width with or without wall enhancement or luminal appendicolith was recognized ([Figure 5] and [Figure 6]). An appendix less than 6 mm in outer diameter was diagnosed as radiologically normal if no other supporting findings were seen and if the appendix was seen with intraluminal air and oral contrast.{Figure 6}

 Results



Twenty-five patients of 100 revealed different diseases other than appendicitis by US and/or CT, like one case of right-sided undisturbed ectopic pregnancy, two cases of mesenteric lymphadenitis, two cases ruptured right ovarian cysts, and 20 cases of right distal ureteric stone, and therefore, they did not undergo appendicectomy. The remaining 75 cases are diagnosed preoperatively as AA by US or CT ([Table 1]). The surgery was done in these 75 cases, and all are confirmed by histopathology as AA.{Table 1}

US diagnosed correctly AA in 70/75 (93.3%) cases confirmed on histopathology. US failed to correctly diagnose appendicitis in five patients because of appendicitis only of tip, subhepatic position, and perforation. CT diagnosed correctly AA in 74/75 (98.6%) cases, which were confirmed on operation and by histopathology. CT could not diagnose appendicitis in one case of appendicitis involving the tip, but it diagnosed the cases of appendicitis in subhepatic appendix and appendicular perforation, which were missed on US ([Table 2]).{Table 2}

 Discussion



According to Alvarado scores, patients with scores of 9 or 10 almost certainly have AA, so the accepted management for these patients is to proceed with appendectomy as soon as possible without further workup. Patients with scores 0–4 have very low chance of having appendicitis and imaging studies are not recommended for them as well. Patients who have scores of 7 and 8 are still very likely to have appendicitis, and those with scores of 5 or 6 are not exactly diagnostic but may still have AA. These clinically equivocal cases need further investigations helping with the diagnosis [9].

CT scan has been shown in many studies to be highly sensitive and specific for diagnosing AA and is dependent on fewer operators [3].

We found in our retrospective study that CT shows mildly higher sensitivity, specificity, and positive predictive value compared with US. According to the study by Reich et al. [10], radiologist-operated US had inferior sensitivity and positive predictive value when compared with CT. According to the study by Jeffrey et al. [11], accuracy of US has brought down the negative laparotomy rate omitted at ∼10%. The sensitivity of graded-compression US technique was found to be 93.3% in our study, and this confirms other results.

Ultrasound (US) is a quick, noninvasive, and low-cost diagnostic modality, and no special patient preparation or contrast material administration is required and is without the hazards of radiation. However, graded compression US is an operator-dependent technique and needs good experience with greater hand skills. There are patient-related factors limiting the diagnostic capability of US such as patient obesity, patients with a retrocecal appendix, and those who have severe abdominal pain, who are hard to study using US. One of the limitations of US is the low sensitivity and specificity in diagnosis of perforated appendicitis [12]. Moreover, other reported possible difficulties in the US diagnosis of appendicitis are focal appendicitis limited to the distal appendix, retrocecal appendicitis, and perforated appendicitis, as appendix decompresses and is then harder to identify on US [3]. In our study, the rate of accuracy of diagnosing AA on US has been high, owing to an expert senior and dedicated sonologist and as only patient with a Alvarado score of more than 5 was taken. Only five cases were missed on US, who were subhepatic, retrocecal appendicitis, and perforated appendix; however, these were diagnosed by CT scans ([Figure 7]), except one.{Figure 7}

CT clearly has its advantages, with sensitivity approaching 100% and the ability to perform the study in a way that is not operator dependent, and in patients in which US is difficult to perform, such as those who are obese. However, the risks of contrast administration, exposure to ionizing radiation, and cost are all limiting factors [10].

Our study shows the multidetector CT is mildly superior to graded compression US in the diagnosis of AA. CT showed a significantly higher sensitivity than US (98 vs. 93.3%). Distal appendicitis (inflammation of only tip of appendix) is a potential cause of false negative CT which may show a normal cecal apex and proximal appendix as in our series one case was missed by CT. A normal appendix is seen more frequently at CT than US, thus CT carries a better true negative value.

CT technique for diagnosing appendicitis varies between authors. Multidetector CT with multiplanar reformatting is more accurate than conventional CT, and the use of oral and/or colonic contrast medium is not essential, although it is necessary to exclude other differential diagnosis. Thus, CT scanning with oral contrast and/or colonic contrast is more accurate than without oral contrast [13]. A focused technique examining the abdominopelvic junction exposes the patient to approximately one-third of the radiation dose of the full abdomen and pelvic examination; however, this technique may not reveal other relevant diagnosis, and thus in some doubtful cases, full abdominopelvic CT may be required [14].

Multidetector CT has reported sensitivities of 90–100%, specificities of 91–99%, accuracies of 94–98%, positive predictive values of 92–98%, and negative predictive values of 95–100% [15].

In our view, graded compression US with posterior manual compression and abdominopelvic MDCT both provide sensitive and accurate diagnosis of AA, and the choice of imaging modality is motivated to some extent by local experience.

US finding should not be interpreted in isolation, as the appendicitis cannot be excluded when an appendix has not been found, and clinical correlation is important as even a negative study does not preclude the diagnosis.

 Conclusion



We found in our study that MDCT has mild superiority over US in the diagnosis of AA; however, the US with expert hands and newer US machines has high sensitivity and specificity in the diagnosis, without the hazards of radiation. If the diagnosis of AA was made on initial US, then CT is not necessary and if not, the MDCT has superiority in the diagnosis of AA in these cases. Similarly, if the diagnosis is confident on plain CT, the enhanced CT scan is not required.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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