A retrocecal appendix is often difficult to identify as high-frequency transducers may fail to appropriately visualize deep structures.21,26,27,29 One can aid in the visualization of the retrocecal appendix by either scanning via a lateral flank approach or by turning the patient to the left lateral decubitus position in order to obtain views posterior to the cecum (Fig. 7).22,29,30 The left lateral decubitus technique may also be helpful in pregnant patients with suspected appendicitis, with this position shifting the uterus away from the RLQ and allowing easier visualization of the appendix.31 Additionally, one author promotes using a 500- to 1,000-cc saline enema for nonvisualization of the appendix in children and cites improved visualization rates with this method in the pelvic, retrocecal, and retroileal position.31
Explore This IssueACEP News: Vol 31 – No 06 – June 2012
A perforated appendix can result in an inconclusive or false-negative study.21,26,27,29 This is likely due to difficulty with adequate compression of the abdomen due to guarding or dilatation of bowel loops as a result of peritonitis and/or the failure to recognize the decompressed appendix after pus evacuation.26
The accuracy of ultrasonography is operator dependent and requires both skill and experience.22-27
The appendiceal diameter should be measured from outer wall to outer wall to obtain an accurate measurement. Additionally, it is important to visualize the entire length of the appendix, including the distal tip, to confirm that it is blind-ending, as the most common cause of misdiagnosed appendicitis by ultrasonography is mistaking the terminal ileum for an inflamed appendix.21,22,27 Visualization of the appendiceal tip is also important so that early appendiceal inflammation, which can often be confined to the distal tip, is not missed.21-29 Finally, other disease entities such as colonic diverticulitis, Crohn’s disease, pelvic inflmmatory disease, epiploic appendagitis, and terminal ileitis can result in false-positive scans.21-29
Bedside ultrasound is helpful in patients with suspected appendicitis to confirm the diagnosis. Further imaging may be warranted if the ultrasound is equivocal.
Dr. Valesky and Dr. Aponte are Ultrasound Fellows in the Department of Emergency Medicine at SUNY Downstate Medical Center. Dr. Secko is a Clinical Assistant Professor in the Ultrasound Division at SUNY Downstate Medical Center. Dr. Mehta is Clinical Assistant Professor and Ultrasound Fellowship Director in the Department of Emergency Medicine, Kings County Hospital Center/SUNY Downstate. Dr. Robert Solomon is Medical Editor of ACEP News and editor of the Focus On series, core faculty in the emergency medicine residency at Allegheny General Hospital, Pittsburgh, and Assistant Professor in the Department of Emergency Medicine at Temple University School of Medicine, Philadelphia.