Appendicitis CT
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Appendicitis Microchapters |
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Diagnosis |
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Appendicitis On the Web |
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American Roentgen Ray Society Images of Appendicitis |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Use as a Diagnostic Tool
- In places where it is readily available, a CT scan has become the diagnostic test of choice for detecting appendicitis, especially in adults whose diagnosis is not obvious on history and physical examination.
- A properly performed CT scan with modern equipment has a detection rate (sensitivity) of over 95% and a similar specificity.
- Signs of appendicitis on CT scan include:
- lack of contrast (oral dye) in the appendix
- direct visualization of appendiceal enlargement (greater than 6 mm in diameter on cross section).
- The inflammation caused by appendicitis in the surrounding peritoneal fat (so called "fat stranding") can also be observed on CT, providing a mechanism to detect early appendicitis and a clue that appendicitis may be present even when the appendix is not well seen.
- Diagnosis of appendicitis by CT is made more difficult in very thin patients and in children, both of whom tend to lack significant fat within the abdomen.
Signs of Appendicitis on a CT Scan
- Appendiceal thickening with the outer-wall-to-outer-wall transverse diameter greater than 6 mm.
- Some authors define appendiceal thickening on CT as transverse diameter greater than 7 mm
- The appendiceal diameter probably should be interpreted in the context of clinical and other
- Appendiceal wall thickening (wall ≥ 3mm)
- Appendiceal wall hyperenhancement
- Mural stratification of the appendiceal wall
- Appendicolith(s) (present in one third of patients with appendicitis).
- Cecal apical thickening (diffuse as opposed to apical cecal thickening is also possible, but this is less specific for appendicitis).
- Periappendiceal inflammation includes periappendiceal fat stranding, thickening of the lateral conal fascia, and mesoappendix, extraluminal fluid, phlegmon, abscess, ileocecal mild lymph node enlargement, and inflammatory thickening of contiguous structures.
Patient #1: Right lower quadrant pain
Patient #2: Right lower quadrant pain
Patient #3: Right lower quadrant pain
Diagnostic Comparsion to Ultrasound
- According to a systematic review from UC-San Francisco comparing ultrasound vs. CT scan, a CT scan is more accurate than ultrasound for the diagnosis of appendicitis in adults and adolescents.
- CT scan has a sensitivity of 94%, specificity of 95%, a positive likelihood ratio of 13.3 (CI, 9.9 to 17.9), and a negative likelihood ratio of 0.09 (CI, 0.07 to 0.12).
- Ultrasonography had an overall sensitivity of 86%, a specificity of 81%, a positive likelihood ratio of 5.8 (CI, 3.5 to 9.5), and a negative likelihood ratio of 0.19 (CI, 0.13 to 0.27).[1]