Ultrasonography and computed tomography in patients with right lower quadrant pain: Difficult cases of appendicitis

R E V I E W
Ultrasonography and computed tomography
in patients with right lower quadrant pain:
Diffi cult cases of appendicitis
Adrienne van Randen1,2
Abstract: Acute appendicitis is a common cause of acute abdomen and both computed tomography
Wytze Laméris1,2
(CT) and ultrasonography (US) are used in the diagnostic work-up of these patients. In general,
Marja A Boermeester2
imaging has high accuracy in diagnosing acute appendicitis. Although the imaging features of
Julien BCM Puylaert3
appendicitis are well known, in some patients fi ndings are less conclusive. This pictorial essay
Jaap Stoker1
will give an overview of diffi cult US and CT cases of patients suspected of acute appendicitis.
Keywords: acute appendicitis, ultrasonography, CT
1Department of Radiology;
2Department of Surgery, Academic
Medical Center, University
Introduction
of Amsterdam, Amsterdam,
The Netherlands; 3Department
Acute abdominal pain, and in particular right lower quadrant (RLQ) pain, is a common
of Radiology, Westeinde Hospital,
patient presentation at the emergency department (ED), usually requiring immediate
The Hague, The Netherlands
diagnostic work-up and care. Acute appendicitis is a common cause for RLQ pain,
although many other diagnoses should be considered. Ultrasonography (US) and
computed tomography (CT) play an important role for a quick and accurate diagnostic
work-up.1 With this pictorial essay we aim to give insight into diffi cult US and CT
cases of patients suspected of appendicitis.
Acute appendicitis
Lifetime risk of developing acute appendicitis is 9% for males and 7% for females.2
Symptoms generally start with nondescriptive visceral pain in the periumbilical region
and anorexia followed by nausea and vomiting. When the disease progresses, typical
migration of the pain to the RLQ occurs because of more localized peritoneal infl am-
mation. Patients with a clear-cut physical history can be diagnosed clinically and may
not require imaging.3 However, diagnosing acute appendicitis may be not that simple,
as negative appendectomy rates of 20% to 30% have been reported for patients who
did not undergo additional imaging after clinical assessment.4,5 However, additional
usage of US and CT can reduce the negative appendectomy rate signifi cantly to 6%.6
Therefore, imaging should be used to confi rm or reject the diagnosis appendicitis, and
in the latter situation propose an alternative diagnosis.
Imaging techniques
US with graded compression is a widely accepted technique for evaluation of the
appendix.7 The CT technique for evaluating an acute abdomen, with a special interest in
Correspondence: Adrienne van Randen
the RLQ, involves a CT of the complete abdomen after intravenous contrast medium.
Academic Medical Center, Meibergdreef
9 suite G1-227, 1105 AZ Amsterdam,
High accuracy (98%) has been reported for focused appendiceal CT with oral and
The Netherlands
rectal contrast medium,8 but the major disadvantage is the possibility of missing an
Tel +31 20 566 2630
Fax +31 20 566 9119
alternative diagnosis outside the volume imaged or an infl amed appendix at an unusual
Email a.vanranden@amc.uva.nl
site (Figure 1). In general, appendicitis can be diagnosed without oral, rectal, or
Reports in Medical Imaging 2009:2 41–47
41
© 2009 van Randen et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access
article which permits unrestricted noncommercial use, provided the original work is properly cited.

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van Randen et al
A
B
Figure 1 A) 20-year-old male suspected for acute appendicitis. Ultrasonography demonstrates in this sagittal oblique image an infl amed appendix (arrow) in the right upper
quadrant with surrounding fat infl ammation (arrowheads) adjacent to the liver and right kidney. B) To guide the operating surgeon, the appendix was marked on the patient’s
skin. The marked point represents the McBurney point.
intravenous contrast medium.9 However, intravenous contrast
Imaging fi ndings of acute
medium facilitates diagnosing alternative diagnoses and may
appendicitis
result in a higher level of confi dence, especially when fat
At US the noninfl amed appendix appears as a compressible,
interfaces are (almost) absent (slim patients) or obliterated
tubular blind-ending structure with a maximum diameter
(areas of infi ltration). Reconstructed images by multiplanar
of 6 mm, without adjacent fat infl ammation (Figure 4).
reformation (MPR) can be of additional help in equivocal
In appendicitis the appendiceal diameter is increased, the
CT scans and increases the radiologist level of confi dence
appendiceal wall is thickened and the surrounding fat is
(Figure 2).10 Plain X-ray does not play a role in the work-up
of patients suspected with appendicitis.11
In current literature CT has higher accuracy compared
to US. In a recent meta-analysis of head-to-head compara-
tive studies of US and CT, a summary sensitivity of 91%
was found for CT and of 78% for US. Specifi city was 90%
for CT and 89% for US.1 In another study by Daly and col-
leagues, 13% (176/1397) of the CT scans performed for
appendicitis were interpreted as equivocal. Of these patients
with an equivocal CT 30% (n = 53) had appendicitis.12 The
sensitivity decreased from 83% to 64% if the equivocal scans
were interpreted as positive, and the specifi city was lowered
from 99.8% to 94% if the equivocal scans were interpreted
as negative.
In our opinion, US should be considered the fi rst modality
of choice in female, young, and slender patients, not only
because of radiation dose, but also because CT scans of
appendicitis in slender patients are more diffi cult to interpret
due to absence of delineating fat. Vice versa, CT is generally
better in obese patients because of the delineating fat planes.
Figure 2 A 39-year-old female with a classical clinical presentation of appendicitis. The
In very obese patients, the extensive amount of fat causes
appendix could not be visualized on ultrasonography, because of disturbing (bowel)
noise on CT, and will therefore not simplify interpretation
air (not shown). sagittal reformatted computed tomography image after iv contrast
medium clearly shows a retrocecal infl amed appendix (arrow); C: cecum. Appendicitis
of CT images (Figure 3).
was confi rmed at surgery and histopathology.
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Diffi cult cases of acute appendicitis
Figure 3 A 37-year-old obese female with a body mass index of 42.7 with histological
Figure 5 A 49-year-old female suspected of acute appendicitis. Ultrasonography
proven appendicitis. CT after iv contrast medium showed a thickened appendix (arrow)
(US) demonstrates a noncompressible, thickened appendix (arrow) surrounded by
and mild adjacent fat infi ltration. C: Cecum.
infl amed mesenteric fat (arrowheads); a clear US diagnosis of acute appendicitis which
was confi rmed at surgery.
hyperechoic, and both the appendix and surrounding fat
(Figure 4). Also in both, complications can be visible, such
are noncompressible (Figure 5). Appendicitis can only
as perforation and abscesses.
be excluded when the appendix is completely visualized,
including the appendiceal tip, and has a normal appearance
Diffi cult cases of US or CT
(Figure 6).
US or CT images are diffi cult to interpret when only one
At CT, a noninfl amed appendix appears as a tubular blind-
or two of the above mentioned imaging features can be
ending structure, usually with a diameter of less than 6 mm,
identifi ed. The solitary fi nding of a thickened appendix, an
and often containing air. Features of an infl amed appendix
appendicolith, or fat infi ltration adjacent to the appendix are
at CT are a tubular, blind-ending structure with a diame-
not conclusive signs for the diagnosis acute appendicitis.12
ter 6 mm which is surrounded by infl amed fat (Figure 7). In
These fi ndings may represent normal fi ndings or may refl ect
both US and CT, an appendicolith can be identifi ed in many
early stages of disease or a reactive response to another
individuals with and without appendicitis, thus the presence
disease in the RLQ. If the treating physician suspects an
of an appendicolith is not pathognomonic for appendicitis
early presentation of appendicitis, a ‘wait-and-see’ policy is
Figure 4 A 23-year-old male with right lower quadrant pain. Ultrasonography
(US) shows a nonthickened appendix (arrows) without surrounding infi ltration and
Figure 6 A 43-year-old male with a surgical and histopathological proven infl ammation
multiple appendicoliths (curved arrows) and therefore not an US (and fi nal) diagnosis
of the appendiceal tip. Ultrasonography images show a normal proximal diameter of
of appendicitis.
the appendix (arrow), but a distal diameter of 8.3 mm (arrowheads).
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van Randen et al
A
Figure 7 A 49-year-old male suspected for appendicitis. Computed tomography
B
(CT) after iv contrast medium shows a thickened appendix (arrow) with a thickened
appendiceal wall, infi ltration of the adjacent fat (arrowheads) and a thickened fat plane
(curved arrow). Appendicitis was proven at surgery and histopathology.
justifi ed, and the patient maybe asked to return the next day
for a second clinical evaluation.
No classical imaging presentation
Single imaging fi nding
Patients with only a thickened appendix and no clinical or
laboratory signs of appendicitis are treated conservatively at
our center, because symptoms may resolve spontaneously,
Figure 8 A 75-year-old male suspected for acute appendicitis. A) Computed
tomography (CT) after iv contrast showed a fl uid fi lled thickened appendix of 10 mm
and may be clinical irrelevant (Figure 8). Patients with mild
diameter (arrow) without infl ammation of the adjacent mesenteric fat, more proximal
fat infl ammation adjacent to a nonthickened or nondistended
to the cecal orifi ce the appendiceal lumen was fi lled with air (not shown) B) An
appendicolith was present at the appendiceal orifi ce (arrow) with cecal wall thicken-
appendix do not have acute appendicitis (Figure 9). In these
ing (arrowheads). On re-examination a few hours later the patient had appetite and
pain had decreased. Therefore the patient was discharged home the next day. After
patients often another diagnosis can be made, while the
more than two years of follow-up, the patient had no recurrent episode of acute right
diagnosis of nonspecifi c abdominal pain (NSAP) is made
lower quadrant (RLQ) pain. Therefore the fi nal diagnosis of nonspecifi c abdominal
pain (NSAP) was made.
when no other clinical and radiological fi ndings are present.
Visualization of a normal appendix is crucial for disregarding
the diagnosis acute appendicitis.
Multiple imaging fi ndings
If patients with RLQ pain have multiple, although subtle,
infl ammatory appendiceal changes or infl ammatory changes
adjacent to the appendix, the diagnosis appendicitis must be
made. If the appendix is thickened and (subtle) fat infi ltra-
tion is present, acute appendicitis is likely. Appendicitis is
also likely when the appendix is somewhat thickened with
an enhancing wall and fat infi ltration (Figures 10, 11). When
a thickened appendix is the sole feature, then the diagno-
sis acute appendicitis is not likely. The only exception is
Figure 9 A 60-year-old female with right lower quadrant (RLQ) pain for three days
a perforated appendix in which the appendix may not be
with a fi nal diagnosis of nonspecifi c abdominal pain after clinical follow-up (up to two
thickened, but adjacent infl ammatory changes are usually
years). Computed tomography (CT) after intravenous contrast shows moderate
streaky fat infi ltration (arrowheads) in the RLQ, but the appendix (arrows) is not
extensive in this situation (Figure 12). In patients with mild
enlarged and contains air (not shown).
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Diffi cult cases of acute appendicitis
infl ammatory changes in the RLQ and without visualization
of the appendix on US and CT, no conclusive diagnosis
can be made and management should be based on clinical
fi ndings and laboratory fi ndings only and laparoscopy can
be considered. However, when the infl ammatory changes
are extensive (possibly abscesses) the appendix may not be
discernable as the fat planes are obliterated (Figure 13). In
this situation the diagnosis appendicitis becomes quite likely
when no other fi ndings (eg, normal terminal ileum visualized)
are present, especially in young men.
Differentiation between terminal ileitis and appendicitis
can be diffi cult when the continuity or blind-ending of an
Figure 10 A 38-year-old male with peri-umbilical pain for 16 hours, nausea without
infl amed tubular structure is not visualized. However when a
vomiting and a low grade temperature was clinically suspected for acute appendicitis.
Computed tomography (CT) after intravenous contrast shows a thickened appendix
normal-appearing ileum and ileocecal region are visualized,
(12 mm) with an appendicolith (arrow) and subtle fat infi ltration (arrowhead). Acute
the diagnosis appendicitis becomes very likely (Figure 14).
appendicitis was confi rmed at surgery and histopathology.
Secondary appendicitis
The appendix may become thickened by an adjacent infl am-
matory condition, such as diverticulitis, a gynecological
cause or an infl ammation in the ileocecal area (Figure 15).
Identifi cation of the primary cause of infl ammation is often
possible, with the infl ammatory response at the primary site
being more extensive than adjacent to the appendix.
Atypical location
A challenge in clinical diagnosing acute appendicitis arises
in patients with atypical history and fi ndings at examination
because of atypical location of the appendix (Figure 1).
In case of a retrocecal appendix, US may have diffi culty
in diagnosing appendicitis as the appendix is obscured by an
Figure 11 A 31-year-old male with right lower quadrant (RLQ) pain for two days,
nausea without vomiting, and rebound tenderness without guarding, was clinically
suspected of acute appendicitis. This computed tomography (CT) image after
intravenous (and oral) contrast shows a curved appendix of 9-mm diameter with
wall enhancement (arrows) and subtle adjacent fat infi ltration (arrowheads). Acute
appendicitis was proven by surgery and histopathology.
Figure 13 A 44-year-old male with right lower quadrant (RLQ) pain suspected for
Figure 12 A 55-year-old female clinically suspected for appendicitis shows an perfo-
acute appendicitis. The appendix could not be visualized on computed tomography
rated appendix (arrow) on this axial computed tomography (CT) image after iv contrast
(CT). This coronal CT image after iv contrast medium demonstrates an abscess
medium. Peri-appendiceal free air is seen (arrows). Also adjacent fat infl ammation, with
(A) with adjacent fat infi ltration (arrowhead) located at the suspected site for the
a thickened fat plane is visible (arrowheads). Surgery and histopathology both proved
appendix and closely related to the cecum (C) and Ileum (I) The abscess was drained
perforated appendicitis in this patient.
percutaneously and no appendectomy was performed.
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van Randen et al
Figure 14 A 33-year-old male with right lower quadrant (RLQ) for one day which
migrated from the peri-umbilical region to the RLQ. Computed tomography (CT) after
intravenous contrast showed an abnormal tubular structure in the RLQ which could
not be visualized completely (arrow). Adjacent to this tubular structure extensive fat
Figure 15 A 27-year-old female with right lower quadrant (RLQ) pain for three days,
infi ltration was seen (arrowheads). Furthermore a normal ileum could be identifi ed
clinically suspected for a gynecological disorder or acute appendicitis. Computed
(not shown). The diagnosis of acute appendicitis was very likely in this male patient,
tomography (CT) after intravenous contrast showed an appendicolith (arrow),
although the blind end of the tubular structure was not visualized. Appendicitis was
extensive fat infi ltration (arrowheads) suggestive of a perforated appendix, although
proven by surgery and histopathology.
the appendix could not be clearly visualized. Perforated appendicitis was proven at
surgery and histopathology.
air-fi lled cecum or ascending colon. At CT visualization is not
A
hampered by appendix localization, provided that no focused
appendiceal CT of the lower quadrants has been performed,
where only part of the abdomen is visualized.
Perforated appendix
Imaging has limitations in identifying a perforated appendix,
although discontinuity of the wall and fl uid adjacent to the
appendix is suggestive for the diagnosis.13 In patients with
frank fat infi ltration, thickened appendiceal wall, but no
distended appendiceal lumen, a perforated appendix should
be considered (Figures 12, 15).
Mimics of appendicitis
B
Alternative diagnoses mimicking acute appendicitis include
right sided diverticulitis (Figure 16), infl ammatory bowel
disease, epiploic appendagitis, and gynecological causes in
women in the reproductive age (Figure 17). Evaluation of spe-
cifi c features of these mimickers are beyond the scope of this
pictorial essay, but are well described in the literature.14,15
Summary
The diagnosis of appendicitis can be readily made at US and
CT, if multiple imaging features of acute appendicitis are
present. In patients with only single or subtle imaging fi ndings
such as a thickened appendix without fat infi ltration, or merely
an appendicolith or fat infi ltration adjacent to the appendix, the
diagnosis of acute appendicitis becomes unlikely and another
Figure 16 A 25-year-old female with acute right lower quadrant (RLQ) pain. A) A
right-sided colon diverticula (arrow) is visible with adjacent fat infi ltration (arrowheads),
cause for their complaints must be sought for. To substanti-
fecolith, wall enhancement on this axial computed tomography (CT) image after i.v.
ate these clinical observations, a prospective study should be
contrast medium; B) Somewhat lower, a nondistended appendix with thickening,
containing air, is visible. The appendiceal wall is secondarily infl amed in this patient
performed evaluating features of appendicitis at imaging.
with right sided diverticulitis. C: Cecum.
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Diffi cult cases of acute appendicitis
3. Andersson RE. Meta-analysis of the clinical and laboratory diagnosis
of appendicitis. Br J Surg. 2004;91:28–37.
4. Jones PF. Suspected acute appendicitis: trends in management over
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Figure 17 A 42-year-old female with acute abdominal pain suspected for acute
of acute appendicitis in patients with equivocal CT fi ndings. AJR Am J
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Roentgenol. 2005;184:1813–1820.
dix (arrow) and a located fl uid collection with wall enhancement suggestive for an
(ovarian) abscess (A), which was in concordance with the fi nal diagnosis of tubo-ovarian
13. Bixby SD, Lucey BC, Soto JA, Theysohn JM, Ozonoff A, Varghese JC.
abscess. The mesenteric fat infl ammation is visible just cranial of the fl uid collection
Perforated versus nonperforated acute appendicitis: accuracy of multi-
(arrowhead) C: cecum; I: ileum.
detector CT detection. Radiology. 2006;241:780–786.
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of acute right lower quadrant pain: part II, uncommon mimics of
appendicitis. AJR Am J Roentgenol. 2005;184:1143–1149.
Disclosure
15. Yu J, Fulcher AS, Turner MA, Halvorsen RA. Helical CT evaluation of
acute right lower quadrant pain: part I, common mimics of appendicitis.
The authors declare no confl icts of interest in this work.
AJR Am J Roentgenol. 2005;184:1136–1142.
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