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JOURNAL OF THE
ROYAL MEDICAL SERVICES

Official Publication for the Jordanian Royal Medical Services

Visualization of Normal Appendix during Non-Contrast Renal CT Scan at King Hussein Medical Centre


Tareq Bisheh MD*, Mazen Humedi MD*, Mohammad Arafat MD*


ABSTRACT

Objective: To evaluate the rate of visualization of normal appendix, its caliber and position among patients without history of prior surgery presenting to the Radiology Department for  non-contrast renal CT scan in stone protocol.

Methods: A total of 125 patients with no history of appendectomy who underwent non-contrast computed tomography scan in stone protocol for evaluation of their renal colic between March and August 2011 were included in this study and their images were reviewed. Identification of normal appendix, its contents and location along with the adequacy of intraperitoneal fat were evaluated in both axial, coronal and sagittal planes.

Results: Normal appendices were visualized in 91.2% of cases. The most common location of appendiceal tip was paracolic, and the maximum outer diameter of the normal appendix ranged between 3 and 9mm (mean 5 ± 1.2 mm).  Intraperitoneal fat was adequate in 71% of the cases.

Conclusion: Most of normal appendices are seen on non-enhanced Multi Detector Computed Tomography scan in stone protocol as identification of normal appendix is critical to exclude the diagnosis of acute appendicitis among patients with right sided abdominal pain.

Key words: Appendicitis, Computed Tomography, Normal appendix

JRMS March 2013; 20(1): 11-14

 

Introduction

The appendix was first described in the 16th century, and in 1886, Reginald Fitz described the term “appendicitis” and emphasized the need for early diagnosis and surgical intervention.(1-3) Acute appendicitis is the most common cause of acute abdominal pain with a lifetime risk reaches 7%  and usually presents in a classical clinical feature in only 60% of cases and the diagnosis is usually based on clinical and laboratory findings except in atypical cases where imaging plays an important role especially ultrasonography (US) and computed tomography (CT).(4-10)

US is widely available, inexpensive and mobile with no need for patient preparation and has no ionizing radiation with reported sensitivity between 76-94%.(2,9) According to a study by Rioux, the detection of normal appendix on US safely rules out appendicitis, however, the negative US scan does not exclude the diagnosis.(9,11)  Magnetic Resonance Imaging (MRI) is also used in cases of suspected appendicitis especially in pregnant women due to lack of ionizing radiation with good reported visualization rate reaching 78%.(12)

With the introduction of multi detector CT (MDCT) technology, visualization of normal appendix was improved as the spatial resolution becomes higher and with the ability to evaluate the appendix by multiplanar reformation images.(4,13)   The rate of visualization of normal appendix ranges from 43% to 91%, with few studies found in the literature addressing this issue.(14,15)


Table I: Appendiceal tip position among the study group

Position

No.

%

Paracolic

51

45

Retrocecal

11

10

Pelvic

16

14

Midline

36

31

 

114

100


Table II: Appendiceal contents

 

No.

%

Air

43

38

Different contents (Fluid, Faecal matter)

69

60

Appendicolith       

2

2


Several studies show that lack of visualization of appendix on CT reliably excludes the diagnosis of acute appendicitis especially in the absence of secondary inflammatory signs and the visualization of normal appendix suggests a normal scan.(14,16,17)

The aim of this study was to evaluate the rate of visualization of normal appendix, its position, content, caliber and the presence or absence of adequate intraperitonial fat at King Hussein Medical Centre (KHMC).

 

Methods

This study was conducted at the Radiology Department at King Hussein Medical Centre between March and August 2011. A total of 125 patients were included in this study, 81 were males and 44 females. The age range was (11-67 years) with median age 46 years. All patients had symptom and signs of urinary tract calculi and presented to the Radiology Department for evaluation of renal colic by non-contrast CT scan in stone protocol. Patients with previous history of appendectomy or who had clinical suspicion of acute appendicitis were excluded from this study.

Examinations were performed using 16-slice MDCT scanner (GE light speed, GE Medical Systems, Milwaukee, Wis.) and 64-slice MDCT scanner (Brilliance, Philips Medical Systems, Cleveland, Ohio). Renal stone protocol included a frontal scout view at 70 KVp and 30 mA, followed by 5-mm slice thickness helical scan from the diaphragm down to symphysis pubis. Scan parameters included: 120 KVp, 250 mA, collimation 0.6 mm, pitch 1, and table speed of 50-mm per rotation. Axial images were reconstructed at 3mm thickness with a 1.5mm increment. Neither oral nor intravenous contrast materials were used.

Reconstructed images reviewed using Picture Archiving and Communicating System (PACS) workstation (IMPAX, Agfa Healthcare, Ridgefield, NJ) and interpretation of images done with axial, coronal and sagittal planes by two experienced radiologists.

The position of caecum was identified with the localization of ileocaecal junction, and then the appendix was identified if visualized. The appendix was interpreted as visualized or non-visualized and its thickness was measured from the area of maximum caliber. The presence of intraluminal air and appendicolith was recorded and the locations of the tip of appendix relative to the caecum were described as paracolic, midline, pelvic and retrocecal. The adequacy of intraperitoneal fat was considered as adequate if fat completely surrounds the caecum.

 

Results

Among patients included in this study, 114 normal appendices were visualized (91.2%). Normal appendix was seen on axial images alone in 110 scans and in four cases confident visualization required coronal and sagittal reformation images. The tip of appendix was most commonly located in paracolic position (45%), followed by midline position (31%). In 14% of cases the position was pelvic and retrocecal in 10% as shown in Table I.

Intraperitonial fat was described as adequate in 89 patients (71%), and inadequate in 36 patients (29%). The luminal contents of visualized appendices included air in 43 patients, fluid and faecal matter in 69 patients (Fig. 1 & 2).   In two cases calcified appendicolith were demonstrated (Table II). The maximum outer diameter of the normal appendix ranged between three and nine mm (mean 5 ± 1.2 mm) and in 85% of cases the outer diameter was greater than 5mm.
Fig. 1: Normal appendix


Fig. 2: Air filled appendix

Discussion

Appendix is a blind-ended tubular structure arising from postero-medial aspect of the caecum with average length 8 cm and variable location of its tip. The pathogenesis of acute appendicitis is luminal obstruction leading to distension, venous and lymphatic congestion with subsequent bacterial invasion of the wall.(18,19)  

Puylaert was first to describe ultrasonographic features of acute appendicitis in 1986, with US being the imaging modality of choice in cases of suspected appendicitis until late 1990’s when CT scan become the most imaging modality used in adults with suspected appendicitis with high accuracy rate.(19,20)   On CT, appendix is seen as thin-walled tubular structure, collapsed or filled with gas or fluid and surrounded by fat. CT criteria of acute appendicitis include thick appendix, periappendiceal fat stranding and wall diameter greater than 6-7mm along with calcified appendicolith.(18,21,22)  The rate of visualization is directly related to age, as it increases with age, probably due to an increase in intra abdominal fat.(23)

This study showed a high visualization rate compared to other studies which is attributed to the use of multiplanar reformates and patient selection regarding age group and appears comparable to the results of other studies.(24)

Only two cases with appendicolith were described in this study which is explained by patients older age group as the presence of appendicolith in children is associated with perforated appendicitis and found in 65% of cases with acute appendicitis, while in adults it is seen less commonly (28%) and can be seen in symptomatic and asymptomatic adults.(25, 26) In view of results of this study, we recommend routine scanning for normal appendix when reporting non contrast renal CT scan.

 

Limitation of our study

The limitation includes lack of surgical correlation as there was no documented pathological report of normal appendix. 

 

Conclusion

Most of normal appendices should be seen on non-enhanced MDCT scan as identification of normal appendix is critical to exclude the diagnosis of acute appendicitis among patients with right sided abdominal pain.

 

References

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2.Lee S, Ho H. Ultrasonography and computed tomography in suspected acute appendicitis. Seminars in ultrasound, CT, and MR 2003; 24(2): 69-73.

3.Ganguli S, Raptopoulos V, Lomlos F, et al. Right lower quadrant pain: Value of the nonvisulaized appendix in patients at multidetector CT. Radiology 2006; 241(1): 175-180.

4.Islam S, Raza S, Irfan A, et al. Visualization of normal appendix on MDCT; questioning the size criteria for appendicitis. PJR  2008; 18(3): .

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6.Tamburrini S, Brunetti A, Brown M et al. CT appearance of normal appendix in adults. Eur Radiol 2005; 15: 2096-2103.

7. Giuliano V, Giuliano C, Pinto F. Rapid Ct scan visualization of the appendix and early acute non-perforated appendicitis using an improved oral contrast method. Emergency Radiology 2004; 10: 235-237.

8. Ng S, Cheng S, Yang F, et al. Hyperdence appendix on unenhanced CT: a sign of acute appendicitis.  Abdom Imaging 2007; 32: 701-704.

9.Simonovsky V. Sonographic detection of normal and abnormal appendix. Clinical Radiology 1999; 54, 533-539.

10.Nitta N, Takahashi M, Furukawa A, et al. MR imaging of the normal appendix and acute appendicitis. Journal of Magnetic Resonance Imaging 2005; 21: 156-165.

11.Peletti A, Baldisserotto M. Optimizing US examination to detect the normal and abnormal appendix in children. Pediatr Radiol 2006; 36: 1171-1176.

12.Nikolaidis P, Hammond n, Marko J et al. Incidence of visualization of the normal appendix on different MRI sequences. Emerg Radiol 2006; 12: 223-226.

13.Kim H, Yang D, Jin W. Identification of the normal appendix in healthy adults by 64-slice MDCT: the value of adding coronal reformation images. The British Journal of Radiology 2008; 81(971):859-864.

14.Keyzer C, Pargov S, Tack D et al. Normal appendix in adults: Reproducibility of detection with unenhanced and contrast enhanced MDCT. AJR 2008; 191: 507–514.

15.Jan Y, Yang F, Huang J. Visualization rate and pattern of normal appendix on multidetector computed tomography by using multiplaner reformation display. J Comput Assist Tomogr 2005; 29: 446-451

16.Johnson P, Horton K, Makesh M, et al. Multidetector computed tomography for suspected appendicitis: Multi-institutional survey of 16-MDCT data acquisition protocols and review of patient literature. J Comput Assist Tomogr 2006; 30: 758-764.

17.Karabulut N, Boyaci N, Yagci B, et al. Computed tomography evaluation of the normal appendix: Comparison of low-dose and standard-dose unenhanced helical computed tomography. J Comput Assist Tomogr 2007; 31: 732-740

18.Cakirer S, Basak M, Colakoglu B, et al. Diagnosis of acute appendicitis with unenhanced helical CT: a study of 130 patients. Emerg Radiol 2002; 9: 155-161.

19.Whitley S, Sookur P, McLean A, et al. The appendix on CT. Clinical Radiology (2009) 64, 190-199.

20.Webb E, Wang Z, Coakley F, et al. The equivocal appendix at CT: prevalence in a control population. Emerg Radiol 2010; 17: 57-61.

21.Benjaminov O, Atri M, Hamilton P, et al. Frequency of visualization and thickness of normal appendix at nonenhanced helical CT. Radiology 2002; 225:400-406.

22.Johnson P, Eng J, Moore C, et al. Multidetector-row CT of the appendix in healthy adults. Emerg Radiol 2006; 12: 248-253.

23.Ozturkmen H, Akpinar E, Ozmen C, et al.  Visualization of the normal appendix in children by non-contrast MDCT. Acta chir belg, 2007; 107: 531-534.

24.Joo S, Lee K, Kim Y et al. Detection of the normal appendix with low-dose unenhanced CT: Use of the sliding slab averaging technique. Radiology 2009; 251: 780-787.

25.Giuliano V, Giuliano C, Pinto F, et al. Chronic appendicitis ”syndrome” manifisted by an appendicolith and thickened appendix presenting as chronic right lower abdominal pain in adults. Emerg Radiol 2006; 12: 96-98.

26.Ghiatas A, Chopra S, Chintapalli K, et al. Computed tomography of the normal appendix and acute appendicitis. Eur Radiol 1997; 7: 1043-1047.

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