Imaging for Acute

Appendicitis

LT David Bruner LCDR Todd Parker

Staff Emergency PhysiciansApril 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

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

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

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 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

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

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

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

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

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 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?

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

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%

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

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%

CasesWhat did you decide to do?

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.”

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