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 Appendectomy Rate (NAR)?

NAR decreased 16% to 6% Guss et al., “Impact of Abdominal Helical CT on the Rate of Negative Appendicitis” JEM 2008; 34(1)

-

NAR decreased mostly due to adult women

Historically 10-20% -

Retrospective review of

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before and after frequent CT

-

Decrease in NAR from 15.5%

 Higher % acceptable in women and peds -

12% CT rate before readily Kim, K. et al, “The Impact of Helical CT on available, 81% after

 With increased imaging

Center Comparison; JEM 2008; 34(1)

 5-10% NAR  Significantly increased pre-operative CT

NAR decreased 20% to 6%

From 32% to 95% - Wegner study

Ultrasound

 Very safe! No radiation, no contrast required    Sensitivity and Specificity:  

appendicitis

- Non-compressible

appendix

Variables: Body habitus, Location, Skill -Free fluid 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

Pros

Oral Contrast

Cons

 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  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

Anderson BA, et al, Am J Surg. Sep 2005 Study type

 Rectal

# of

Systematic review of 23 studies 5

Sens

97

Spec

97

Accura

97 Oral 2 83 95 92 Oral +  Over 3700 patients over 16 years old NonCon 2 7 8 95 93 93 96 92 98 96 92 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 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  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 • • • 4 had appendicitis – MRI correctly dx all 3 inconclusive – clinically resolved spontaneously perforation occurs    MRI has good sensitivity and specificity in 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 imaging – take to the OR   

“The routine use of CT for adult male and pediatric patients with a clinical picture suggestive of acute appendicitis should therefore be 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