Localization of the Appendix at MR Imaging during Pregnancy: Utility of the Cecal Tilt Angle

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Abstract
To determine whether the cecal tilt angle on sagittal magnetic resonance (MR) images in pregnant patients correlates with the location of the appendix and gestational age and whether the cecal tilt angle can help predict the location of the appendix. This HIPAA-compliant retrospective study was approved by the institutional review board. Informed consent was waived. Of 146 consecutive pregnant patients suspected of having appendicitis (mean age, 29 years) who underwent MR imaging, 143 had MR images in which the appendix and cecum were identifiable in the sagittal plane. Two observers reviewed the MR images; findings were agreed upon by consensus. With use of sagittal single-shot fast spin-echo MR images, the cecal tilt angle was calculated as the angle between the imaging table and a line drawn between the cecal tip and the luminal center of the most proximal inflection point in the ascending colon. The location of the appendiceal base relative to the lumbosacral spine was recorded. Statistical analyses were performed by using Spearman and Pearson correlation coefficients to evaluate the relationship among gestational age, appendiceal base location, and cecal tilt angle. Receiver operating characteristic curve analysis was performed to assess the ability of the cecal tilt angle to help differentiate between a high and low appendiceal base level. Cecal tilt angles showed moderate correlation with appendiceal base levels (Spearman correlation coefficient, 0.44; P < .001) and poor correlation with gestational age (Pearson correlation coefficient, 0.25; P = .002). Regardless of gestational age, cecal tilt angles of at least 90 degrees were predictive of a high appendiceal base level with a specificity of 98% (95% confidence interval: 92%, 100%). The cecal tilt angle is useful for localizing the appendix in pregnant patients at MR imaging and helps predict the location of the appendix within the right upper quadrant of the abdomen with high specificity, irrespective of gestational age.

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