Appendiceal CT in pediatric patients: Relationship of visualization to amount of peritoneal fat

OBJECTIVE. This study was performed to determine the rate of visualization of the nor mal pediatric appendix on CT and to evaluate the relationship of the appendix to parameters such as amount of intraperitoneal fat, use of c ontrast material, patient age, and slice thickness. MATERIALS AND METHODS. Three board-certified radiologists retrospectively r eviewed 248 successive pediatric abdominal and pelvic CT examinations perfo rmed from 1995 to 1999. Each radiologist independently assessed the degree of intraperitoneal fat (minimal, moderate, or marked compared with a standa rd slice), appendiceal visualization (definite, unsure, not seen), cecal an d terminal ileal opacification, and the outer diameter of visualized append ixes. The age and sex of the patient, collimation thickness (3-10 mm), and use of enteric or IV contrast material was also recorded. RESULTS. A normal appendix was identified in 120 (48.4%) of 248 examination s. The only individual variable with statistically significant correlation was the degree of intraperitoneal fat. This was determined using the Pearso n chi-square test, the likelihood ratio, and logistic regression. The appen dix was seen in 68.8% (n = 93) of patients with moderate or marked intraper itoneal fat versus 36.1% in = 155) with minimal fat (p < 0.001). A trend to ward decreased visualization in children younger than 10 years old with min imal peritoneal fat was identified and confirmed with a 95% confidence limi t. The outer diameter of the visualized appendix varied from 3 to 10 mm, wi th a mean value of 6 mm. CONCLUSION. Increased peritoneal fat significantly increases the rate of id entification of the normal appendix in pediatric patients. Although less fa t is generally seen in younger patients, there is significant overlap of ap pendix visualization among age groups.