What are the findings of a computed tomography (CT) scan of the abdomen showing a ruptured appendix?

From the Guidelines

A ruptured appendix on a CT scan of the abdomen is a medical emergency that requires immediate attention, and treatment typically involves emergency surgery and intravenous antibiotics. The diagnosis of a ruptured appendix on a CT scan is based on several key findings, including an enlarged, thickened appendix with surrounding inflammation, free fluid, and possibly an abscess [ 1 ]. The appendiceal wall may show discontinuity or perforation, and there is often fat stranding and inflammatory changes in the surrounding tissues. Air bubbles outside the appendix are a key finding indicating perforation [ 1 ].

Key Findings on CT Scan

• Enlarged, thickened appendix with surrounding inflammation
• Free fluid and possibly an abscess
• Discontinuity or perforation of the appendiceal wall
• Fat stranding and inflammatory changes in the surrounding tissues
• Air bubbles outside the appendix

Treatment

• Emergency surgery (either open or laparoscopic appendectomy)
• Intravenous antibiotics (such as piperacillin-tazobactam 3.375g IV every 6 hours or a combination of ceftriaxone 1-2g daily and metronidazole 500mg every 8 hours)
• Fluid resuscitation
• Possibly drainage of any abscesses

Complications

• Peritonitis
• Sepsis
• Abscess formation

The use of CT scans with IV contrast is recommended for the diagnosis of acute appendicitis in elderly patients, as it can help distinguish between perforated and non-perforated appendicitis [ 1 ]. The risk of contrast-induced acute kidney injury (CI-AKI) should not discourage the use of CT scans with IV contrast in this population, as the benefits of prompt diagnosis and treatment outweigh the risks [ 1 ].

CT Scan with IV Contrast

• Recommended for the diagnosis of acute appendicitis in elderly patients
• Can help distinguish between perforated and non-perforated appendicitis
• Risk of CI-AKI should not discourage use in elderly patients

From the Research

CT Scan Findings for Ruptured Appendix

• A ruptured appendix can be detected on a CT scan of the abdomen, with findings such as appendiceal dilatation (appendiceal diameter ≥7 mm) or presence of appendicoliths 2.
• CT findings of appendicolith, mass effect, and a dilated appendix greater than 13 mm are associated with higher risk of treatment failure (≈40%) of an antibiotics-first approach 2.
• The appendiceal diameter is larger in patients with ruptured appendicitis than in those with simple appendicitis (13.2 +/- 3.2 vs 11.3 +/- 2.4 mm, P < .001) 3.
• Abscess, extraluminal air, wall defect, peritoneal enhancement, extraluminal appendolith, phlegmon, localized fluid, fascial thickening, ascites, stool impaction, and 4 patterns of bowel wall thickening are significant CT signs for predicting appendiceal rupture 3.

Diagnostic Accuracy of CT Scan

• The sensitivity and specificity of CT for diagnosing appendicitis in adults are high, with summary sensitivity of 0.95 (95% CI 0.93 to 0.96) and summary specificity of 0.94 (95% CI 0.92 to 0.95) 4.
• Unenhanced standard-dose CT appears to have lower sensitivity than standard-dose CT with intravenous, rectal, or oral and intravenous contrast enhancement 4.
• CT scanning without rectal contrast is effective for the diagnosis of acute appendicitis, with a sensitivity of 90%, specificity of 98%, accuracy of 94%, positive predictive value of 98%, and negative predictive value of 91% 5.

Clinical Factors for Predicting Appendiceal Rupture

• Longer duration of symptoms, peritoneal sign, and higher C-reactive protein are significant clinical factors for predicting appendiceal rupture in acute appendicitis 3.
• The size of the appendicolith is larger in patients with ruptured appendicitis than in those with simple appendicitis (7.1 +/- 4.4 vs 5.1 +/- 2.8 mm, P = .018) 3.