Imaging

Appendicitis

Preliminary Diagnosis: Appendicitis

I. What imaging technique is first-line for this diagnosis?

  • CT scan of the abdomen and pelvis with IV and without oral contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of appendicitis.

Advantages

  • CT scanning is diagnostic for appendicitis and can detail any secondary complications such as periappendiceal abscesses, intraperitoneal free air, or inflammation of the surrounding visceral structures.

  • CT scans are relatively quick imaging modalities that require minimal patient cooperation and are less susceptible to patient motion artifact.

  • CT scans are the best imaging modality to localize an obstructing luminal tumor.

Disadvantages

  • RIsks of CT scans include exposure to ionizing radiation.

  • CT scans may be safely performed with IV contrast if the creatinine is 1.6 or less. If the creatinine is >1.6, contrast is administered at the discretion of the supervising physician and may be decreased in amount, not given, or administered in conjunction with excessive IV normal saline.

III. What are the contraindications for the first-line imaging technique?

Patients with allergies to IV contrast (mild, moderate, and severe) should be pretreated with a combination of antihistamine and/or steroids according to standard protocol.

CT scanning is contraindicated in pregnant patients, especially within the first two trimesters.

IV. What alternative imaging techniques are available?

  • Alternative imaging options include the following: ultrasound (gray scale and color Doppler), MRI, radiography (plain film), and fluoroscopy (barium enema).

  • For allergies to IV contrast material, if emergent imaging is needed, as often is the case for patients with suspected appendicitis, a CT scan without IV contrast may be performed. It is the most efficient, expedient, and useful imaging modality in patients with severe IV contrast allergy. Other options, although less optimal, include ultrasound and MRI.

  • For pregnant patients, ultrasound is the first imaging modaliity choice, followed by MRI.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of appendicitis.

Ultrasound

Advantages

  • May be diagnostic in appendicitis

  • Color Doppler may depict hyperemia of an inflammed appendix.

  • Relatively inexpensive, quick, and portable imaging modality that does not use ionizing radiation

Disadvantages

  • Ultrasound imaging may be futile in visualizing deep visceral abdominal and pelvis structures in obese patients.

  • Limited in detailing any secondary complications from a primary appendicitis

MRI

Advantages

  • In the correct setting with multiple positive pertinent clinical findings, an MR exam may be diagnostic for appendicitis.

  • MRI does not make use of ionizing radiation and may be peformed in pregnant patients.

  • Secondary complications from appendictis may be visualized on MR exams.

Disadvantages

  • MRI is expensive and requires much patient cooperation due to long imaging acquisition times.

Plain abdominal radiographs

Advantages

  • Plain film imaging may suggest appendicitis in the correct clinical situation with multiple positive radiographic findings.

  • The combination of abdominal pain and visualization of an appendicolith is associated with a 90% probability of acute appendicitis.

Disadvantages

  • Only risk from plain radiography is exposure to ionizing radiation.

  • Barium enema may be suggestive of the diagnose in the setting of positive pertinent symptoms and multiple diagnostic imaging findings.

  • Non filling of the appendix is normal in one-third of the patients.

  • Barium enema exposes a patient to more radiation than plain radiographs and less than CT.

  • Barium enema examinations are operator dependent.

VI. What are the contraindications for the alternative imaging techniques?

  • No significant contraindications to plain radiography or ultrasonography exist.

  • MRI is contraindicated in patients with non-MR-compatible hardware.

  • Barium enema examination is contraindicated in those patients with bowel perforation.

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