Imaging for Acute
Appendicitis
LT David Bruner
LCDR Todd Parker
Staff Emergency Physicians
April 2009
Objectives
 Cases
 Consider what you would do
 Imaging choices
 US
 CT
 Non-contrast vs oral contrast vs rectal
 MRI
 Reconsider Cases/Discussion
Case 1
 15 yo male - 1 day worsening abdominal pain
 Periumbilical  migrated to RLQ
 Nausea, vomiting, anorexia, hurts to walk, no fever
 RLQ guarding / rebound / Heel Tap / Rovsing
 Labs:
 WBC – 8.9 H/H – 12/37
 UA – 12 WBC, Pos Leuk Est, rare bacteria
 What imaging, if any?
Case 2
 8 yo f - >24 hrs of worsening RLQ pain
 Diarrhea and nausea, subjective fever
 Urinary frequency / abdominal pain with micturition
 T – 101.0
P – 121
BP – 108/62
 RLQ TTP at McBurney’s point
 Guard/mild rebound
 UA Negative
WBC – Pending
Case 3
 37 yo man - 30 hours of worsening RLQ pain
 N/V and Fever to 100.5
 No urinary symptoms
 PMHx of kidney stones – but this is different
 Wife and daughter recently sick with N/V/D
 RLQ TTP with guarding and rebound
 UA Negative
 Does he need a CT?
 If so, what kind
Case 4
 31 yo female - 2 days worsening pain
 Epigastric at first, now only RLQ
 Nausea, subjective fever, menses
 No urinary symptoms
 Positive McBurney’s, Rovsing, Heel Tap
 No CMT or adnexal masses felt
 HCG negative, UA negative
 Imaging?
Case 4-1
 Same as Case 4 except . . . .
 No vaginal bleeding
 HCG Positive
 ED US reveals IUP at 10 weeks
 Imaging?
Case 5
 73 yo female
 30 hours lower abdominal pain and nausea
 No vomiting /diarrhea, fever, bloody stool, or dysuria
 Hx of HTN
 Otherwise negative PMHx and PSHx
 Bilateral Lower Quad TTP R > L, mild guarding
 P – 98
T – 100.8
BP – 135/76
Clearly Imaging Reduces NAR
Wagner et al., Surgery. 2008; 144(2)
 Acceptable Negative
Guss et al., “Impact of
Appendectomy
Abdominal Helical CT on the
Rate of Negative
Appendicitis” JEM 2008; 34(1)
- Retrospective review of four-year time
(NAR)?
periodsRate
before and
after frequent CT
- NAR decreased 16% to 6%
- NAR decreased mostly due to adult women
- Retrospective review of
- No change in NAR with kids (8%)
before and after frequent CT
 male
Historically
10-20%
- Adult
decreased from
9% to 5% (NSS)
- Decrease in NAR from 15.5%
- Adult women decreased 20% to 7%
to 7.6%
 Higher % acceptable in women and
peds
- 12% CT rate before readily
Kim, K. et al, “The Impact of Helical CT on
available, 81% after
Negative Appendectomy Rate: A Multi With increased imaging
Center Comparison; JEM 2008; 34(1)
 5-10% NAR
- CT Rate and NAR inversely related
 Significantly increased pre-operative CT
- NAR decreased 20% to 6%
 no
From
32%
- Wegner
- Limited by
follow
up to
on 95%
negative
scans study
Ultrasound
 Very safe! No radiation, no contrast
required
 Sensitivity and Specificity:

Findings on US for
Adult - Sensitivity – 74-83%, Specificity
– 93-97%
appendicitis
- Non-compressible
 Pediatrics – Sensitivity -88%,
Specificity – 94%
appendix
- Appendix >6mm diameter
 Variables: Body habitus,
Location,
Skill
- Signs
of perforation
-Free fluid
-Abscess
 If can’t visualize – need to
move on to the
next step
Computed Tomography
 High overall accuracy, Sens, Spec, NPV, and PPV
 Available at all hours
 Risks:
 Radiation
 Contrast problems
 Allergic reactions
 Nephrotoxicity
Oral Contrast
Pros
 Sensitivity 94-98% /
specificity 95-99%
 Alternative diagnoses
 May see extravasation
 Better if little intra-
abdominal fat
 Fluid collections
 Comfort with reading
contrasted vs noncontrasted
Cons
 Large volume contrast
 What if vomiting?
 If not, probably will
 Risk of aspiration
 Aren’t they NPO?
 Increases difficulty of
assessing bowel wall
 2 hour delay
 Delays surgical decision
 Risk of perforation
 4-8 hrs to advance
Rectal Contrast CT
 Gravity drip – little risk of perforation
 Few minutes to perform scan
 As little as 15 minutes
 Accuracy equal to oral contrast
 No reported increased discomfort
Rectal contrast study
 Berg ER, et al, Acad Emerg
Med. 2006 Oct; 13(10)
 Compared oral and rectal
contrast CT in a randomized
trial
 Stephen AE, et al., J Ped
Surg. Mar 2003; 38(3)
 96/283 kids had rectal
contrast
 Showed decreased length
 95% Sens and PPV
 No increased patient
 Missed cases still went
of stay in the ED by one hour
discomfort between oral or
rectal contrast
 Equal diagnostic accuracy.
to OR because of
clinical scenario
Non-Contrast CT
 For diagnosis of appendicitis
 No need to drink contrast – no delay
 No change in diagnostic accuracy with IV
Contrast
 Sensitivity 94-98%
Specificity – 95-99%
 Significant supporting evidence for non-
contrast CT in suspected appendicitis
Lane MJ, et al, Radiology. 1999; 213
 300 consecutive patients
 Non-contrast CT for appendicitis
 Compared with surgical pathology results
 96% sensitive
 99% specific
 97% accuracy
 “Stacked the Deck”
Hoecker CC, et al, JEM. May 2005
 Retrospective study 112 children
 Atypical presentation (13% of total abd pain pts)
 CT’d without PO contrast (helical CT)
 40% positive appendicitis rate
 Compared to those given PO contrast (prev
studies)
 Equal sensitivity and specificity in both groups
 Overall 91% diagnostic accuracy
Lowe LH, et al., Am J Roent. Jan 2001
 Retrospective cohort of 72 children with
non-contrast CT (atypical PE)
 97% sensitive (95% CI, 91-100%)
 100% specific (95% CI, 96-100%)
 Only took 5 minutes to perform the study
Lowe, L. H., et al, Radiology 2001; 221
 75 consecutive patients - non-contrast CT
 Atypical/Equivocal PE findings
 Compared residents’ and attendings’ reads
 Results:
 91% agreement in reading studies
 96% specificity and 88% accuracy in residents
 98% specificity and 97% accuracy in attendings
 Attendings more confident of reads
Ege G, et al., Br J Radiology. 2002; 75
 296 adults non-con CT for suspected appendicitis
 Equivocal Exams Only
 45% positive for appendicitis
 Compared with surgical pathology or follow up
 96% sens and 98% spec/ 97% PPV and 98% NPV
 Recommends non-con CT for diagnosis of appendicitis in
adults
 Negative study requires observation or follow up
Anderson BA, et al, Am J Surg. Sep 2005
Study
type
# of
studies
Sens
Spec
Accura
cy
 Systematic review of 23 studies
Rectal
5
97
97
97
(19 prospective,
4 retrospective)
Oral
2
83
95
92
Oral +
2
95
96
96
Rectal
 Over 3700 patients over 16 years
Oralold
+ IV
7
93
92
92
NonCon
8
93
98
96
Oral vs
None
92 vs 94 95 vs 97 92 vs 96
IV Contrast
 Basak S, et al., J Clin Imag. 2002; 26.
 Performed study without contrast then with contrast
 No difference in making the diagnosis with IV or no
contrast
 Some even thought IV obscured the intra-abdominal
structures
 Keyzer, C., et al, Am J Roent. August 2008
 Equal agreement between resident and attending
reads
 Equal ability to visualize the appendix
Alternative Diagnoses?
 Likely the most compelling argument
 What are the data?
 No good head to head studies
 Plenty of data showing that both
enhanced and unenhanced find
alternative diagnoses
 Which is best?
Alternative Diagnoses in NonContrasted Studies
 Malone, A. et al, Am J Roentgen 1993
 35% alternative diagnosis
 Diverticulitis, Ovarian Cysts or masses, PID, IBD
 Lane MJ, et al, Radiology. 1999
 21% alternative diagnosis
 Ureteral Calculi, Diverticulitis, Chron’s, Mesenteric Adenitis,
Neoplasms
 Alternative diagnoses advocated by IV and Oral/Rectal
contrast
 Epiploic appendagitis, diverticulitis, Meckel’s Torsion,
gynecologic disorders, obstructive uropathy, RLL PNA
 How much advantage does contrasted vs non-contrasted
study provide?
Why Scan at All?
 Kalliakmans V, et al., Scan J Surg. 2005; 94(3)
 717 adults evaluated for appendicitis by 6 surgeons
 Normal practice patterns - recorded decisions
 11% Negative appendectomy rate based on
history, physical, and labs
 CT did not change diagnostic accuracy except
in cases of atypical history and physical
 Recommends only using CT in equivocal cases
CT in Pediatrics
 Increased lifetime cancer risk
 Less intra-abdominal fat
Garcia K, et al, Radiology. Feb 2009
 Is a negative CT enough?
• 1139 pediatric cases over 4 years
• CT results compared to surgical pathology or follow up
• All except 8 had CT with IV contrast only
• NPV (non-visualized appendix) – 98.7%
• NPV (Visualized) – 99.8%
• NPV (Partially visualized) – 100%
What About MRI?
 Pros: No radiation and can do reconstructions
 Cons: Cost, Time, not always available 24/7
 Highly accurate, operator dependent
 Sensitivity 93-99% Specificity 94-100%
 Less robust evidence, but most studies show
reliable and reproducible diagnostic accuracy
 Caution with gadolinium if pregnant
Pregnancy and Appendicitis
Pedrosa, I et al, Radiology. Mar 2006
 Same incidence as non-pregnant
• 51 consecutive pregnant pts suspicion for appendicitis
 Questionable evidence of appendix moving out of
RLQ • Underwent MRI if US inconclusive
• 4 had appendicitis – MRI correctly dx all
 Risk
surgery/anesthesia
less than
risk of mortality to
• 3of
inconclusive
– clinically is
resolved
spontaneously
mother and fetus if appendicitis is missed or
• Sens – 100% / Spec – 93.6% / Accuracy – 94%
perforation
occurs
Pedrosa,
I et al,
Radiology.
 Want
to avoid
radiation
risks toMar
fetus2009
– right?
 US
miss appendix
in a different
location
• may
148 consecutive
pregnant
pts suspicion
for appendicitis
• Underwent
140/148
hadspecificity
ultrasoundin
first
 MRI
has goodMRI,
sensitivity
and
appendicitis
• 14 had appendicitis – MRI correctly dx all, U/S 5/14
• 9 False-Positives
• Sens – 100% / Spec – 93% / PPV – 61% / NPV – 100%
Cases
 What did you decide to do?
Case 1 – 15 yo male with 1 day
of pain, migration, and peritonitis
 No
– take
“Theimaging
routine use
of CT to
for the
adultOR
male and
 Kalliakmans V, et al., Scan J Surg. 2005; 94(3
pediatric patients with a clinical picture
 suggestive
Guss DA, et of
al.,acute
JEM. appendicitis
2008; 34(1) should
 Wagner
PL, et al.,be
Surgery.
2008 Aug; 144(2)
therefore
discouraged.”
 All showed
no improved negative appy
rate for males with pre-operative CT scanning.
Case 2 – 8 yo girl, 1 day of pain,
peritoneal signs, fever
 Actual case
 US done first
 Then an MRI was performed
 Then went to the OR
 Recommendation in this case
 US or straight to the OR
 CT vs MRI if still unsure
Another case
 13 year old girl
 Ultrasound Positive Appy
 Straight to the OR
Case 3 – 37 yo male, 36 hours of
pain, RLQ ttp, fever, hx of stones
 Non-contrast CT
 What if his WBC count was 19.5 with a
left shift?
 No imaging . . . To the OR?
Case 4 – 31 yo female, good
exam, negative urine
 Do you want to avoid radiation?
 Could start with US
 Could go directly to CT
 Little reason for MRI
Case 4-1 - Pregnant
 US first
 MRI vs CT
 Serial exams
Dose of radiation thought to be teratogenic and increase risk of cancer in
fetuses is 50 mGy
ACOG gives CT a level 2 recommendation
- Must weigh risks and benefits
Case 5 – 73 yo woman
 Non-contrast CT
 What if her Creatinine is 2.2?
 Does she need IV Contrast
Take home points
 Classic presentations do not require imaging
 Reserve imaging for equivocal cases
 Abdominal CT estimated increase cancer risk 1 in 2000
 CT not shown to decrease NAR in men and children
 Multiple studies suggest oral contrast provides no added
value – no need to make them drink
 Consider US first for kids, women, and pregnant
 MRI is a reasonable alternative if available
 Can CT pregnant women safely – inform of risks
 Consider Informed Consent in certain cases
Discussion