Radiologic Diagnosis of Appendicitis

Arabinda Pani, HMS III Gillian Lieberman, MD

Radiologic Diagnosis of Appendicitis

Arabinda Pani, Harvard Medical School, Year III

Gillian Lieberman, MD

January 2005

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Overview• Introduction: Epidemiology, Pathophysiology• Role of Radiologic diagnosis• Normal anatomy• Appearance in various modalities• Criteria for radiologic diagnosis• Patient Case: Appendicitis in Pregnancy

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Epidemiology

•Appendicitis-associated abdominal pain is a common presentation to ED•Peak Incidence: 10 – 30 years of age •Lifetime incidence: 7% in United States•Historically, high rate of false negatives and false positives

•20% of diagnoses initially missed•20% of appendectomies revealing a normal appendix

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Pathophysiology• The lumen of the appendix becomes obstructed,

leading to increased intraluminal pressure resulting in inflammation, ischemia, and infection

• Obstruction is most often secondary to: • Appendicoliths• Lymphoid hyperplasia• Parasite infections• Tumors (carcinoid, metastatic)• Foreign bodies

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Complications of Appendicitis

• Perforation • Abscess formation• Generalized peritonitis• Small bowel obstruction

The rate of complications increases with time until diagnosis and treatment.

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Classic Presentation

• Dull, generalized abdominal pain, migrates to RLQ over 24 hours

• Nausea, Vomiting, Anorexia

• Low-grade fever• Abdominal tenderness• Guarding• Rebound tenderness• Obturator and Psoas

Signs • Elevated WBC

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Role of Radiologic Diagnosis• Appendicitis is highly

prevalent• Often presents

atypically especially in children, women and the elderly

• Complications are common and time- dependent

Radiologic Diagnosis:• Is effective in significantly increasing diagnostic accuracy• Decreases morbidity and mortality by:

•preventing complications•avoiding unnecessary surgeries

• Lowers the overall cost of healthcare

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Anatomy

Gray’s Anatomyadam.com

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Normal Appendix

contrast-filled appendix on barium study contrast in appendix (CT)

http://www.emedicine.com/radio/topic47.htm

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Ultrasound: Normal Appendix

Longitudinal ultrasonography shows compressible tubular structure with an outer diameter of less than 6 mm. A=Iliac artery; V=Iliac vein.

http://emedicine.com/radio/topic47.htm

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Normal Appendix: MR

Courtesy Dr. Eric Zeikus, PACS:BIDMC

Low Signal Intensity

Non-distended

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Radiologic Findings of Appendicitis• Inflammatory changes • Lumenal obstruction• Appendicoliths

Plain FilmFilm is normal in > 50% of patients with appendicitis

Only 10% demonstrate a calcified, laminated appendicolith(s)

Other findings are non- specific

Barium EnemaDiagnostic criteria requires visualization of a non- filling appendix

Often non-diagnostic with low sensitivity

Invasive

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Plain Film: Calcified Appendicolith

http://telesalud.ucaldas.edu.co

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Graded Compression Ultrasound•Blind-ended, tubular, noncompressible, aperistaltic structure

•Diameter > 6 mm, laminated wall

•Increased periappendiceal echogenicity

•Appendicolith: echogenic with distal shadowing

•Doppler: increased circumferential flow

•Perforation/Abscess: thickening of adjacent bowel wall, fluid collections, hypoechoic mass

Overall diagnostic accuracy: 85%

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Appendicitis on Ultrasound

Non-compressible, blind-ended

8mm diameter

Laminated wall

Birnbaum B A, and Wilson S R. Appendicitis at the Millennium. Radiology 2000 215: 337-348.

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Color Doppler Ultrasound


Circumferential Flow, suggestive of hypervascularity and inflammation

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Appendicolith on US


• Bright, echogenic focus

• Clean distal acoustic shadowing

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Perforated Appendix on US

http://lunis.lumc.edu/radiology/Appendicitis

• Perforated Appendix with Free Peritoneal Fluid (FF) surrounding loops of bowel (B).

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CT DiagnosisPrimary Criteria:

• Enlarged, inflamed appendix– diameter >6 mm in

adults – > 8mm in children

• Appendicolith• Non-contrast filled

Secondary Criteria:• Wall enhancement • Fat stranding • Abscess formation • Focal thickening of the

cecum (arrow-head sign) • Adenopathy• Small bowel obstruction • Free fluid in the pelvis

Overall Accuracy: 98%

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Uncomplicated Appendicitis: CT

Courtesy of Dr. Michael Geary, PACS: BIDMC

• Non-contrast filled• Enlarged appendix,

14 mm in diameter• Adjacent fat stranding

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Coronal CT: Enhancing Wall

PACS: BIDMC

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CT: Appendicolith

http://www.madisonradiologists.com/SvcCTAbdominalPain.htm

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Arrowhead Sign

http://lunis.lumc.edu/radiology/Appendicitis/ctfindings.htm

Mural thickening of the cecum at the base of an obstructed appendix

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Periappendiceal Abscess

Courtesy of Dr. Damon Soeiro; PACS: BIDMC

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Coronal CT: Abscess

PACS: BIDMC

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Our PatientOtherwise healthy, 33 year old female at 20 weeks gestation, presented to ED with 6 days of abdominal pain.

Pain was described as epigastric and crampy in nature.

Denied nausea, vomiting. Reported loss of appetite, chills, and a low-grade fever.

Temp 99.4 WBC: 10.2

Abdomen: soft, gravid, diffusely tender to palpation; no rigidity or rebound tenderness

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Diagnostic Complications in Pregnancy

• Pregnancy alters the position of the appendix

• Atypical clinical presentation

• Increased risk of perforation

• Association with premature labor, decreased birth weight

•Ultrasound is modality of choice but diagnosis can be impeded by body habitus and anatomic displacement of the appendix•CT exposes the fetus to radiation

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Patient Evaluation by Ultrasound• Focal rounded area of

increased echogenicity with a hypoechoic rim and increased vascularity suspicious for an inflamed appendix

• Localized to the patient’s area of tenderness

• Noncompressible

PACS: BIDMC

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Doppler Ultrasound Findings

• Transverse view demonstrated increased circumferential flow in the wall of the appendix, suggestive of hypervascularity secondary to inflammation

PACS: BIDMC

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Diagnosis of Appendicitis in Pregnancy

Diagnostic Findings• Enlarged appendix >

6mm• Periappendiceal

inflammatory changes• T2/fat-suppressed

images: high signal intensity of an inflamed appendix

Advantages of MR•Visualize an abnormal appendix in atypical locations•Visualize adjacent inflammatory processes•Different sequences +/- contrast •No known biologic risks to fetus

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HASTE Sequence, Coronal View

• Appendix location: posterior and superior to the uterus

• Distended at: 10 mm in the middle; 18 mm at tip

• Associated fat stranding

Courtesy of Dr. Eric Zeikus, PACS: BIDMC

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Sagittal View

• Fluid-filled lumen

• Thickened wall

PACS: BIDMC

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Conclusion of Case• Patient proceeded to surgery for a laparoscopic

appendectomy, performed without complications.• On gross appearance, the appendix was inflamed

and gangrenous. • Post-op ultrasound demonstrated a normal,

unchanged fetus.• Pathology: specimen consistent with acute

appendicitis with evidence of perforation• The mother carried fetus to term, delivered

without complications.

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Acknowledgements• Michael Geary, MD• Arati Khanna, MD• Damon Soeiro, MD• Atif Zaheer, MD• Eric Zeikus, MD• Gillian Lieberman, MD• Pamela Lepkowski• Larry Barbaras

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References• Birnbaum B A, and Wilson S R. Appendicitis at the Millennium. Radiology 2000

215: 337-348. • Checkoff JL, Wechsler RJ, Nazarian LN. Chronic Inflammatory Appendiceal

Conditions That Mimic Acute Appendicitis on Helical CT. Am. J. Roentgenol. 2002 179: 731-734

• Cobben LP, Groot I, Haans L et al. MRI for Clinically Suspected Appendicitis During Pregnancy. Am. J. Roentgenol. 2004 183: 671-675

• Eyvazzadeh AD, Pedrosa I, Rofsky N M et al. MRI of Right-Sided Abdominal Pain in Pregnancy. Am. J. Roentgenol. 2004 183: 907-914

• Lee J, Jeong YK, Hwang JC, et al. Graded Compression Sonography with Adjuvant Use of a Posterior Manual Compression Technique in the Sonographic Diagnosis of Acute Appendicitis Am. J. Roentgenol. 2002 178: 863-868.

• Novelline, RA. Helical CT in Emergency Radiology. Radiology 1999 213: 321- 339.

• Rosen MP, Sands DZ, Esterbrook H, et al. Impact of Abdominal CT on the Management of Patients Presenting to the Emergency Department with Acute Abdominal Pain. Am. J. Roentgenol. 2000 174: 1391-1396

• Somani R, Gordon C, McArthur R. Appendicitis in pregnancy: a rare presentation. CMAJ 2003 168: 1020

• Wise SW, Labuski MR, Kasales CJ, et al. Comparative Assessment of CT and Sonographic Techniques for Appendiceal Imaging Am. J. Roentgenol. 2001 176: 933-941

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Radiologic Diagnosis of Appendicitis