Surgical Science, 2011, 2, 109-116
doi:10.4236/ss.2011.23022 Published Online May 2011 (http://www.scirp.org/journal/ss)
109
Computed Tomography Diagnosis of Acute
Appendicitis—Pictorial Essay
Aarthi Govindarajan, Bhawna Dev, Roy Santosham, Santhosh Joseph
Department of Ra di ol o gy a nd Im aging Sciences, Sri Ramachandra Medical College and Research Institute,
Sri Ramachandra University, Chennai, India
Received October 11, 2010; revised December 25, 2011; accepted April 11, 2011
Abstract
Acute appendicitis is a common surgical emergency with varied clinical presentations. Early diagnosis is
absolutely necessary to minimize morbidity whereas delayed or missed diagnosis can cause adverse conse-
quences. Computed tomography is a highly accurate imaging technique for diagnosing appendicitis. Hence it
plays a valuable role in selected patients with suspected appendicitis; [1]. In this essay, we review the normal
Computed tomography anatomy of the appendix and the right lower quadrant and illustrate the Computed
tomography signs of appendicitis and important differential diagnostic entities. The Computed tomography
appearance of complications of acute appendicitis is also presented, as are issues concerning clinical presen-
tation and duration of the symptoms. Computed tomography signs can be varied and overlooked as they say
what is easy to see is also easy to miss.
Keywords: Acute Appendicitis, Multislice Computed Tomography
1. Introduction
Acute appendicitis is the commonest cause of acute ab-
domen pain which needs surgical intervention. Atypical
symptoms, varied presentations and multiple differen-
tials of abdomen pain make accurate diagnosis of appen-
dicitis difficult clinically.
Non enhanced & contrast enhanced Computed tomo-
graphy images are helpful in noninvasive evaluation of
appendicitis. The Computed tomography diagnosis of
acute appendicitis has high positiv e and negative predic-
tive values, 96% and 95% [2], respectively. It is also
possible to reconstruct the entire form and position of
appendices from successive Computed Tomography f ind-
ings with high-resolution thin-slice Multidetector com-
puted tomography images [3].
2. Normal Anatomy
Appendix is a narrow worm shaped blind ending tube
arising from the caecum. Appendix is highly mobile and
variable in length by up to 20 cm [4]. It can be retrocae-
cal, subcaecal, pelvic, preileal and post ileal in location.
Most common is the retrocaecal position [5]. Appendix
has a triangular mesentery, the meso appendix. Appen-
dix is supplied by appendicular artery, a branch of ileo-
colic artery and venous drainage is through ileocolic
vein into the superior mesenteric vein.
3. Cases with Detailed Description
(a) (b)
Figure 1. Non enhanced (a) and Enhanced (b) shows nor-
mal blind ending appendix arising from the caecum.

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
3.1. Case I Computed Tomography Appearance
of Normal Appendix
Patient came for evaluation of renal calculi and Computed
tomographic images showed normal appendix as smooth
thin walled tubular organ (arrow) surrounded by mesen-
teric fat (Figures 1(a) and 1(b)). Transverse diameter of
normal appendix should not exceed 6 mm without in-
traluminal material, but some authors considered an upper
limit of 10 mm with intraluminal content [6].
3.2. Case II Acute Appendicitis
Patient presented to Emergency Room with periumblical
pain and vomiting for 2 days and Computed Tomo-
graphic images showed inflammed appendix with peri-
appendicular mesenteric stranding (Figures 2(a), 2(b),
2(c) and 2(d)).
3.3. Case III Retrocaecal Appendicitis with
Lateral Conal Fascia Thickening and
Retroperitoneal Abscess
Patient was referred from Emergency Room to rule out
acute appendicitis and Computed Tomography showed
retrocaecal long inflammed appendix with adjacent re-
troperitoneal abscess (Figures 3(a), 3(b), 3(c), 3(d), 3(e)
and 3(f))
3.4. Case IV Long inflammed Appendix with
Midline Extension
Patient with right iliac fossa pain and fever for 3 days.
Computed Tomographic images showed long appendix
crossing the midline with features of acute appendicitis
(Figures 4(a), 4(b) and 4(c)).
3.5. Case V Appendicolith without Inflammation
Patient presented with right iliac fossa pain for 2 days
and Computed Tomographic showed appendicolith with
no evidence of appendix enlargement/periappendicular
stranding (Figures 5(a) and 5(b))
3.6. Case VI Appendicolith with Inflammation
Patient complained of lower abdomen pain with vomit-
ing. Computed Tomography showed enlarged thickened
appendix with minimal periappendicular mesenteric
stranding seen. (Figures 6(a) and 6(b)).
3.7. Case VII Base Appendicitis
Patient presented with lower abdomen pain and Com-
puted Tomography showed acute inflammation at the
take off of appendix from caecum with minimal strand-
ing (Figures 7(a) and 7(b)).
3.8. Case VIII Terminal Appendicitis with
Perforation and Pneumoperitoneum
Patient presented with dull aching right iliac fossa pain
and Computed Tomographic images showed thickened
tip of appendix with mesenteric stranding (Figures 8(a),
8(b) and 8(c)).
(a) (b) (c) (d)
Figure 2. (a) Non-enhance d axial section of computed tomography shows diffuse thickening of distal cae cum with surround-
ing inflammatory mesenteric stranding (arrow); (b) Non enhanced Computed Tomography shows enlarged and thickened
appendix (arrow) with luminal diameter 11 mm in its cross section. (c) Non enhanced axial Computed Tomography shows
appendicolith (arrow) measuring 9 mm within the lumen. (d) Coronal section of Non Contrast Enhanced Computed Tomo-
graphy abdomen shows pericolic mesenteric fat stranding with thickening of distal ileal loops and caecum (arrow head) and
appendicolith within the lumen (arrow).

A. GOVINDARAJAN ET AL. 111
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Figure 3. (a) Non enhanced axial Computed Tomography shows periappendicular stranding (arrow) at the level of take off of
appendix from caecum. (b) Non enhanc ed axial Computed Tomography shows thickened appendix with transverse diameter
of 1.3 cms (arrow). (c) & (d) Non enhanced (c)and enhanced (d) axial Computed Tomography shows small loculated abscess
(c, arrow) in retro peritoneum adjacent to thickened appendix showing enhancement after contrast administration (d, arrow).
(e) Thickened retrocaec al appendix (small arrow) leading to thickened right lateral conal fascia (arrow) with multiple mesen-
teric lymph nodes (arrow head). (f) Contrast Enhanced Computed Tomography oblique images shows long retrocaecal thick-
ened appendix (arrow) (1.3 cm) extending up to posterior renal fascia.
3.9. Case IX Appendicular Mass
Right Iliac Fossa pain for 2 weeks and Computed Tomo-
graphic images showed heterog eneous mass in right iliac
fossa with thickening of ascending colon and distal il-
eum (Figures 9(a), 9(b) and 9(c)).
3.10. Case X Appendicular Abscess
Lower abdomen pain for 2 weeks and Computed Tomo

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
Figure 4. (a) Nonenhanced Computed Tomography shows 10 cm long edematous appendix (arrows) crossing the midline with
luminal diameter 1.2 cm, w ith surrounding fat stranding. Line ar appendicolith (Small arrow) is seen within the lumen. Small
pericolic fluid collection (arrowhead) is seen anterior to caecum. (b) Enhanced axial Computed Tomography shows Large
fluid collection (Arrow) anterior to rectum with attenuation similar to bladder. (c) Enhanced coronal Computed Tomogra-
phy shows long inflammed appendix (arr ows) with periappendicular str anding. Fluid collection (arrow head) seen in pelvis.
(a) (b)
Figure 5. (a) Non enhanced axial Computed tomography
shows appendicolith (arrow) noted within appendix lumen.
(b) Coronal oblique images of Computed Tomography ab-
domen shows noninflammed appendix (arrow) with faeco-
lith.
(a) (b)
Figure 6. (a) Non enhanced axial Computed Tomography
shows fluid filled thickened appendix with appendicolith
(arrow) at the neck of appendix. (b) Saggital oblique nonen-
hanced images shows fluid filled appendix with appendico-
lith.
graphy showed irregular thick walled abscess with ap-
pendix not separately visualized (Figures 10(a) and
10(b)).
3.11. Case XI Acute Appendicitis with Contained
Perforation
Patient complained of acute abdomen pain for 2 days

A. GOVINDARAJAN ET AL. 113

(a) (b)
Figure 7. Axial nonenhanced (a) and Saggital oblique images shows thickening at its origin (10 mm). Body and tip of ap-
pendix (arrow head) is normal. Minimal ascites noted in right iliac fossa. (a, small arrow)
Figure 8. (a) Nonenhanced coronal Compute d Tomography shows thickened tip (arrow head) with appendicolith within and
adjacent fat stranding. Base of appendix (arrow) is nor mal. (b) Non enhanced axial Computed Tomography shows appe ndi-
colith (arrowhead) noted at the tip with surrounding mesenteric stranding. (c) Axial non enhanced Computed Tomography
shows small pneumoperi tone um (ar row) in right sub diaphragmatic space.

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114

Figure 9. Axial nonenhanced (a) and enhanced (b) axial Computed Tomography shows complex heterogeneous mass in the
right iliac fossa (arrow) .Wall enhancement noted on contrast administration (b arrow). Large 14 mm appendicolith (arrow
head) within the mass. (c) Right iliac fossa shows heterogeneous mass (arrow) fluid filled appendix (arrow) with appendico-
th (arrowhead) within the lumen. li
(a) (b)
Figure 10. Nonenhanced (a) and enhanced (b) axial Com-
puted Tomography shows ill-defined heterogeneous mass (a,
arrow) in right iliac fossa. On contrast injection, wall en-
hancement (b, arrow) seen with necrotic areas within.
and Computed Tomography taken showed perforated ap-
pendix with adjacent air pockets(Figures 11(a) and 11(b)).
3.12. Case XII Mucocele of Appendix
Patient presented with mild lower abdominal pain for 1
(a) (b)
Figure 11. Axial nonenhanced (a) and enhanc ed cor onal (b)
Computed Tomography show s thickened appendix (arrow)
at its take off from caecum with surrounding inflammed
mesentery. Small Faecolith noted at the base. Focal gas
pockets (arrowhead) noted adjacent to the appendix.
week and Computed Tomographic images showed
distended edematous fluid filled appendix with appen-
dicolith and air pockets within (Figures 12(a) and
12(b)).

A. GOVINDARAJAN ET AL. 115

(a) (b)
Figure 12. Nonenhanced (a) and enhanced (b) axial Com-
puted tomography shows enlarged, edematous (10 mm)
fluid filled appendix(arrow) with appendicolith (small
arrow) in the base and few air pockets (a, arrowhead) seen
within. Enhancement of appendicular wall (b, arrow) in
Contrast Enhanced Computer Tomogr aphy.
4. Pathophysiology
The pathophysiology of appendicitis is the constellation
of processes that leads to the development of acute ap-
pendicitis from a normal appendix. Appendicitis results
due to obstruction of the appendiceal lumen. The main
source of obstruction include lymphoid hyperplasia due
to infection in the gastrointestinal tract and occasionally
by inflammatory bowel disease (Crohn’s disease and
ulcerative colitis), feces, parasites, or growths that clog
the appendiceal lumen and trauma to the abdomen
Understanding the pathophysiology helps to explain all
the signs and symptoms and the complications seen in
appendicitis. In all the cases, independent of etiology, the
main thrust of events is increase in the pressu re within the
lumen followed by continuous secretion of fluids and mu-
cus and the stag nation of this mater ial leading to co mpro-
mised blood supply and becoming very vulnerable to in-
vasion by bacteria found in t he gut norm all y.
The pathophysiology [7] involved in inflammation of
appendix is as follows:
Luminal Obstruction
↓
Continuous Secretion of Mucus
↓
Raised Intraluminal Presume with Distended Lumen
↓
Reduced Venous Supply
↓
Arterial Compromise with Ischemia
↓
Micro Perforation & Bacterial Colonization
5. Discussion

Appendicitis is an acute inflammation of the vermiform
appendix, typically resulting in abdominal pain, anor exia,
and abdominal tenderness
Computed Tomography Criteria for Diagnosing
Acute Appendicitis: Computed Tomography is a highly
accurate and effective cross-sectional imaging technique
for diagnosing and staging acute appendicitis. Abdomi-
nal and pelvic Computed Tomography scanning with or
without oral & intravenous contrast can be done, de-
pending upon radiologist preference. However targeted
Computed Tomography technique for evaluation of ap-
pendix is done in all the cases strongly suspicious of
appendicular pathology. Computed Tomography scan-
ning has the advantage of direct visualization of the ap-
pendix, periappendiceal region and other intra-abdominal
structures.
There are primary as well as secondary signs for diag-
nosing appendicular pathologies on cross sectional imag-
ing.
Primary signs
Enlarged Unopacified Appendix
Abnormal Thickened Appendix
Abnormal Enhancement on CECT
Periappendicular Fat Stranding [8]
Secondary signs
Mesenteric Adenopathy
Appendicolith
Caecal Bar Sign—Focal Caecal Wall Thickening [9-11].
Arrow Head Sign—Arrowhead Shaped Collection of
Contrast in Upper Part of Caecum near the Orifice of
Appendix [9-11].
Para Colic Gutter Fluid
Diffuse Caecal Wall Thickening
Abscess/Extra Luminal Air
The inflamed appendix usually measures 7 - 15 mm in
diameter. Circumferential and symmetric wall thicken-
ing is always present and is best demonstrated on images
obtained with intravenous contrast material enhancement.
Homogenous enhancement of thickened wall is seen.
Other important findings include focal cecal apical
thickening and the arrowhead sign (cecal contrast mate-
rial funnels symmetrically at the cecal apex to the point
of appendiceal occlusion). This secondary finding may

A. GOVINDARAJAN ET AL.
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116
help to establish the diagnosis in equivocal cases.
Enlargement of the appendix with associated fluid and
loculated air within the lumen is seen in Gangrenous
appendicitis.
Perforated appendicitis is usually accompanied by pe-
ricecal phlegmon or abscess formation. Other findings
include extraluminal air, marked ileocecal thickening,
localized lymphadenopathy, peritonitis, and small-bowel
obstruction.
6. Conclusions
Computed Tomography can show a normal appendix as
well as various other ways appendicitis can appear [12].
It is the accurate modality for the diagnosis of acute ap-
pendicitis, especially in patien ts with equivocal presenta-
tion. Radiologist must be aware of various clinical and
radiological features of these presentations which aid in
faster diagnosis and optimize treatment of these patients.
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