Normal appendix in adults: reproducibility of detection with unenhanced and contrast-enhanced MDCT

The purposes of this study were to investigate whether readers' interpretations are reproducible and whether readers are confident in identifying a normal appendix with CT and to assess the influence of patient characteristics and IV contrast enhancement on visualization of the appendix.

One hundred two patients without a history of abdominal surgery underwent unenhanced and contrast-enhanced CT for the evaluation of cancer. Three radiologists with varying degrees of experience read scans twice in separate sessions. They were asked to identify the appendix, to score their confidence in identification, and to mark the appendix on the images. Intraabdominal fat volume was measured with a computer-assisted method. Independent experts compared the readers' markings and indicated whether the findings were reproducible.

Reproducibility differed significantly between reading sessions (p < 0.001) and readers (p = 0.003). On the images of 71% of the patients, there was perfect intrareader and interreader agreement with statistically significant and positive influences of patient body mass index (p = 0.005) and intraabdominal fat volume (p = 0.001). Contrast enhancement influenced intrareader reproducibility only for the reader who made less-reproducible interpretations (p = 0.033). Intrareader and interreader agreement in categorizing confidence in identification of the appendix ranged from fair to good (kappa = 0.221-0.620). Confidence was not influenced by contrast enhancement (p = 0.433-0.953), body mass index, or intraabdominal fat volume (p = 0.058-0.798).

Reproducibility in identifying a normal appendix is reader dependent. Perfect intrareader and interreader agreement in marking the appendix occurs approximately 70% of the time and increases with patient body mass index and intraabdominal fat volume. Contrast enhancement does not influence the rate of identification of the appendix or reader confidence but may influence the reproducibility of findings.