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Imaging for Acute
Appendicitis
LT David Bruner LCDR Todd Parker
Staff Emergency PhysiciansApril 2009
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Objectives
Cases Consider what you would do
Imaging choices US CT
Non-contrast vs oral contrast vs rectal MRI
Reconsider Cases/Discussion
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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?
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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
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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
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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?
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Case 4-1
Same as Case 4 except . . . .
No vaginal bleeding
HCG Positive
ED US reveals IUP at 10 weeks
Imaging?
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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
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Clearly Imaging Reduces NAR
Acceptable Negative Appendectomy Rate (NAR)?
Historically 10-20%
Higher % acceptable in women and peds
With increased imaging 5-10% NAR Significantly increased pre-operative CT
From 32% to 95% - Wegner study
Wagner et al., Surgery. 2008; 144(2) - Retrospective review of four-year time periods before and after frequent CT- NAR decreased 16% to 6%- NAR decreased mostly due to adult women- No change in NAR with kids (8%)- Adult male decreased from 9% to 5% (NSS)- Adult women decreased 20% to 7%
Kim, K. et al, “The Impact of Helical CT on Negative Appendectomy Rate: A Multi-Center Comparison; JEM 2008; 34(1) - CT Rate and NAR inversely related- NAR decreased 20% to 6%- Limited by no follow up on negative scans
Guss et al., “Impact of Abdominal Helical CT on the Rate of Negative Appendicitis” JEM 2008; 34(1) - Retrospective review of before and after frequent CT- Decrease in NAR from 15.5% to 7.6%- 12% CT rate before readily available, 81% after
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Ultrasound Very safe! No radiation, no contrast
required
Sensitivity and Specificity:
Adult - Sensitivity – 74-83%, Specificity – 93-97%
Pediatrics – Sensitivity -88%, Specificity – 94%
Variables: Body habitus, Location, Skill
If can’t visualize – need to move on to the next step
Findings on US for appendicitis
- Non-compressible appendix- Appendix >6mm diameter- Signs of perforation
-Free fluid-Abscess
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Computed Tomography
High overall accuracy, Sens, Spec, NPV, and PPV
Available at all hours
Risks:
Radiation
Contrast problems
Allergic reactions
Nephrotoxicity
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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 non-contrasted
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
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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
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Rectal contrast study
Berg ER, et al, Acad Emerg Med. 2006 Oct; 13(10)
Compared oral and rectal contrast CT in a randomized trial
Showed decreased length of stay in the ED by one hour
No increased patient discomfort between oral or rectal contrast
Equal diagnostic accuracy.
Stephen AE, et al., J Ped Surg. Mar 2003; 38(3)
96/283 kids had rectal contrast
95% Sens and PPV
Missed cases still went to OR because of clinical scenario
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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
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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”
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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
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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
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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
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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
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Systematic review of 23 studies (19 prospective, 4 retrospective)
Over 3700 patients over 16 years old
Study type
# of studie
s
Sens Spec Accuracy
Rectal 5 97 97 97
Oral 2 83 95 92
Oral + Rectal
2 95 96 96
Oral + IV
7 93 92 92
NonCon 8 93 98 96
Oral vs None
92 vs 94
95 vs 97
92 vs 96
Anderson BA, et al, Am J Surg. Sep 2005
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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
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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?
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Alternative Diagnoses in Non-Contrasted 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?
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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
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CT in Pediatrics
Increased lifetime cancer risk
Less intra-abdominal fat
Is a negative CT enough? Garcia K, et al, Radiology. Feb 2009
• 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%
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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
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Pregnancy and Appendicitis
Same incidence as non-pregnant
Questionable evidence of appendix moving out of RLQ
Risk of surgery/anesthesia is less than risk of mortality to mother and fetus if appendicitis is missed or perforation occurs
Want to avoid radiation risks to fetus – right?
US may miss appendix in a different location
MRI has good sensitivity and specificity in appendicitis
Pedrosa, I et al, Radiology. Mar 2006
• 51 consecutive pregnant pts suspicion for appendicitis• Underwent MRI if US inconclusive
• 4 had appendicitis – MRI correctly dx all• 3 inconclusive – clinically resolved spontaneously• Sens – 100% / Spec – 93.6% / Accuracy – 94%
Pedrosa, I et al, Radiology. Mar 2009
• 148 consecutive pregnant pts suspicion for appendicitis
• Underwent MRI, 140/148 had ultrasound first• 14 had appendicitis – MRI correctly dx all, U/S 5/14• 9 False-Positives• Sens – 100% / Spec – 93% / PPV – 61% / NPV – 100%
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CasesWhat did you decide to do?
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Case 1 – 15 yo male with 1 day of pain, migration, and
peritonitisNo imaging – take to the OR
Kalliakmans V, et al., Scan J Surg. 2005; 94(3 Guss DA, et al., JEM. 2008; 34(1) Wagner PL, et al., Surgery. 2008 Aug; 144(2)
All showed no improved negative appy rate for males with pre-operative CT scanning.
“The routine use of CT for adult male and pediatric patients with a clinical picture suggestive of acute appendicitis should
therefore be discouraged.”
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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
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Another case
13 year old girl
Ultrasound Positive Appy
Straight to the OR
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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?
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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
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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
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Case 5 – 73 yo woman
Non-contrast CT
What if her Creatinine is 2.2? Does she need IV Contrast
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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
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Discussion