Emergency Radiology

, Volume 20, Issue 1, pp 51–56

The prevalence and patterns of intraluminal air in acute appendicitis at CT

  • Miguel Cabarrus
  • Yee-Li Sun
  • Jesse L. Courtier
  • Joseph W. Stengel
  • Fergus V. Coakley
  • Emily M. Webb
Original Article


The purpose of this study is to investigate if the presence and distribution of intraluminal air in the appendix contributes to the computed tomography (CT) diagnosis of appendicitis. We identified 100 consecutive patients (57 men and 43 women; mean age, 38) with CT prior to appendectomy for acute appendicitis over a 5-year period and a control group of 100 consecutive patients (29 men and 71 women; mean age, 39) who underwent CT for acute abdominal pain without appendicitis. Patients were scanned using multidetector row CT scanners at 1.25 or 5-mm slice thickness, peak tube voltage of 120 kVp, and milliamperse automatically adjusted to attain a noise index of 12. Ninety-two of 100 study patients and 95 of 100 controls received 150 mL intravenous contrast. Two independent readers noted the presence and distribution pattern of intraluminal air in the appendix, appendiceal diameter, wall hyperemia, wall thickening (>3 mm), and wall stratification and presence of any secondary signs of appendicitis including fat stranding and free fluid. Data were compared between groups using Fisher’s exact test and Student’s t test. Intraluminal air in the appendix was more common in control patients versus patients with appendicitis (66 of 100 versus 27 of 100, p < 0.001). No significant differences in the patterns of intraluminal air were found between cases and controls. Among appendicitis cases, there was no significant difference in mean appendiceal diameter (12.8 versus 12.0, p = 0.20) or number of CT signs of appendicitis (1.93 versus 1.86, p = 0.78) in cases with intraluminal air versus without. No case of appendicitis demonstrated intraluminal air without secondary signs of appendicitis. Although intraluminal air is sometimes assumed to exclude a diagnosis of appendicitis, it is actually a common finding seen in up to 27 % of cases at CT. The pattern of intraluminal air was not helpful in differentiating a normal appendix from appendicitis.


Acute appendicitis CT Intraluminal air 


  1. 1.
    Choi D, Park H, Lee YR et al (2003) The most useful findings for diagnosing acute appendicitis on contrast-enhanced helical CT. Acta Radiol 44(6):574–582PubMedGoogle Scholar
  2. 2.
    Ives EP, Sung S, McCue P et al (2008) Independent predictors of acute appendicitis on CT with pathologic correlation. Acad Radiol 15(8):996–1003PubMedCrossRefGoogle Scholar
  3. 3.
    Rao PM, Rhea JT, Novelline RA (1997) Sensitivity and specificity of the individual CT signs of appendicitis: experience with 200 helical appendiceal CT examinations. J Comput Assist Tomogr 21(5):686–692PubMedCrossRefGoogle Scholar
  4. 4.
    Whitley S, Sookur P, McLean A et al (2009) The appendix on CT. Clin Radiol 64(2):190–9PubMedCrossRefGoogle Scholar
  5. 5.
    Moteki T, Horikoshi H (2007) New CT criterion for acute appendicitis: maximum depth of intraluminal appendiceal fluid. AJR Am J Roentgenol 188(5):1313–1319PubMedCrossRefGoogle Scholar
  6. 6.
    Moteki T, Ohya N, Horikoshi H (2009) Prospective examination of patients suspected of having appendicitis using new computed tomography criteria including “maximum depth of intraluminal appendiceal fluid greater than 2.6 mm”. J Comput Assist Tomogr 33(3):383–389PubMedCrossRefGoogle Scholar
  7. 7.
    Gale ME, Birnbaum S, Gerzof SG et al (1985) CT appearance of appendicitis and its local complications. J Comput Assist Tomogr 9(1):34–37PubMedCrossRefGoogle Scholar
  8. 8.
    Rao PM, Rhea JT, Novelline RA (1997) Appendiceal and peri-appendiceal air at CT: prevalence, appearance and clinical significance. Clin Radiol 52(10):750–754PubMedCrossRefGoogle Scholar
  9. 9.
    Rettenbacher T, Hollerweger A, Macheiner P et al (2000) Presence or absence of gas in the appendix: additional criteria to rule out or confirm acute appendicitis—evaluation with US. Radiology 214(1):183–187PubMedGoogle Scholar
  10. 10.
    Kim HC, Yang DM, Kim SW, Park SJ (2012) Reassessment of CT images to improve diagnostic accuracy in patients with suspected acute appendicitis and an equivocal preoperative CT interpretation. Eur Radiol 22(6):1178–85PubMedCrossRefGoogle Scholar
  11. 11.
    Killen DA, Brooks DW Jr (1965) Gas-filled appendix: a roentgenographic sign of acute appendicitis. Ann Surg 161:474–478PubMedCrossRefGoogle Scholar
  12. 12.
    Lim MS (1977) Gas-filled appendix: lack of diagnostic specificity. AJR Am J Roentgenol 128(2):209–210PubMedGoogle Scholar
  13. 13.
    Musgrove JE (1952) Unusual roentgenographic findings in gangrenous appendicitis. Can Med Assoc J 67(6):666–667PubMedGoogle Scholar
  14. 14.
    Johnson PT, Eng J, Moore CJ, Horton KM, Fishman EK (2006) Multidetector-row CT of the appendix in healthy adults. Emerg Radiol 12(6):248–53PubMedCrossRefGoogle Scholar
  15. 15.
    Tamburrini S, Brunetti A, Brown M et al (2005) CT appearance of the normal appendix in adults. Eur Radiol 15(10):2096–2103PubMedCrossRefGoogle Scholar
  16. 16.
    Webb EM, Wang ZJ, Coakley FV et al (2010) The equivocal appendix at CT: prevalence in a control population. Emerg Radiol 17(1):57–61PubMedCrossRefGoogle Scholar
  17. 17.
    Levine CD, Aizenstein O, Wachsberg RH (2004) Pitfalls in the CT diagnosis of appendicitis. Br J Radiol 77(921):792–799PubMedCrossRefGoogle Scholar
  18. 18.
    Daly CP, Cohan RH, Francis IR et al (2005) Incidence of acute appendicitis in patients with equivocal CT findings. AJR Am J Roentgenol 184(6):1813–1820PubMedGoogle Scholar
  19. 19.
    Stengel JW, Webb EM, Poder L et al (2010) Acute appendicitis: clinical outcome in patients with an initial false-positive CT diagnosis. Radiology 256(1):119–26PubMedCrossRefGoogle Scholar
  20. 20.
    Landis JR, Koch GG (1977) The measurement of observer agreement for categorical data. Biometrics 33(1):159–174PubMedCrossRefGoogle Scholar
  21. 21.
    Balthazar EJ, Megibow AJ, Siegel SE et al (1991) Appendicitis: prospective evaluation with high-resolution CT. Radiology 180(1):21–24PubMedGoogle Scholar
  22. 22.
    Funaki B, Grosskreutz SR, Funaki CN (1998) Using unenhanced helical CT with enteric contrast material for suspected appendicitis in patients treated at a community hospital. AJR Am J Roentgenol 171(4):997–1001PubMedGoogle Scholar
  23. 23.
    Kamel IR, Goldberg SN, Keogan MT et al (2000) Right lower quadrant pain and suspected appendicitis: nonfocused appendiceal CT—review of 100 cases. Radiology 217(1):159–163PubMedGoogle Scholar
  24. 24.
    Malone AJ Jr, Wolf CR, Malmed AS et al (1993) Diagnosis of acute appendicitis: value of unenhanced CT. AJR Am J Roentgenol 160(4):763–766PubMedGoogle Scholar
  25. 25.
    Raman SS, Lu DS, Kadell BM et al (2002) Accuracy of nonfocused helical CT for the diagnosis of acute appendicitis: a 5-year review. AJR Am J Roentgenol 178(6):1319–1325PubMedGoogle Scholar
  26. 26.
    Rao PM, Rhea JT, Novelline RA et al (1997) Helical CT technique for the diagnosis of appendicitis: prospective evaluation of a focused appendix CT examination. Radiology 202(1):139–144PubMedGoogle Scholar
  27. 27.
    Rao PM, Rhea JT, Novelline RA et al (1997) Helical CT combined with contrast material administered only through the colon for imaging of suspected appendicitis. AJR Am J Roentgenol 169(5):1275–1280PubMedGoogle Scholar

Copyright information

© Am Soc Emergency Radiol 2012

Authors and Affiliations

  • Miguel Cabarrus
    • 1
  • Yee-Li Sun
    • 1
  • Jesse L. Courtier
    • 1
  • Joseph W. Stengel
    • 1
  • Fergus V. Coakley
    • 1
  • Emily M. Webb
    • 1
  1. 1.Department of Radiology and Biomedical ImagingUniversity of California San FranciscoSan FranciscoUSA

Personalised recommendations