{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T22:53:13Z","timestamp":1768863193498,"version":"3.49.0"},"reference-count":16,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,17]],"date-time":"2026-01-17T00:00:00Z","timestamp":1768608000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University of Alberta, Department of Radiology and Diagnostic Imaging Summer Studentship"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background\/Objective: Recent North American guidelines suggest that CT is indicated for further evaluation where ultrasound (US) is negative, although the negative predictive value (NPV) of ultrasound in adult patients when the appendix is not seen remains unclear. To assess the negative predictive value (NPV) of ultrasound in adult patients when the appendix is not seen. Methods: A scoping review of MEDLINE and EMBASE was performed from inception to 13 May 2025 using PRISMA-ScR guidelines to identify studies evaluating the outcome of adult patients where the appendix is not seen on ultrasound, with preference for studies where there were no secondary signs of acute appendicitis (right lower quadrant free fluid, abscess, ileus, echogenic fat or regional lymphadenopathy). Original studies with at least 10 patients were included in the review. The reference standard included a combination of clinical follow-up, CT and\/or pathology. Data synthesis was provided as a qualitative review of the existing literature. Results: Six studies were included in the review. The number of included patients range from 12 to 179 with a mean age of 29\u201338 years. Few studies reported the patient BMI. NPVs ranged from 80 to 90% for all indeterminate ultrasounds and 83 to 95% for studies where secondary signs of appendicitis were excluded (90 to 95% when non-surgical reference standards were included). Two studies reported NPVs of 96\u2013100% when the pre-test probability was low. Conclusions: The NPV of indeterminate ultrasound for adult patients with right lower quadrant pain and no secondary signs of appendicitis is likely \u226590%. When combined with a low clinical suspicion, the NPV is likely &gt;95%. The appropriateness of a subsequent CT indication when the appendix is not visualized on ultrasound should be determined on an individualized basis.<\/jats:p>","DOI":"10.3390\/diagnostics16020304","type":"journal-article","created":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T09:57:02Z","timestamp":1768816622000},"page":"304","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Not All Patients Need a CT When the Appendix Is Not Seen on Ultrasound: A Scoping Review"],"prefix":"10.3390","volume":"16","author":[{"given":"Ali","family":"Ramji","sequence":"first","affiliation":[{"name":"Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB T6G 2R3, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-7769-4147","authenticated-orcid":false,"given":"Justin J. Y.","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB T6G 2R3, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4959-8934","authenticated-orcid":false,"given":"Gavin","family":"Low","sequence":"additional","affiliation":[{"name":"Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB T6G 2R3, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Karim","family":"Samji","sequence":"additional","affiliation":[{"name":"Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB T6G 2R3, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1630-5138","authenticated-orcid":false,"given":"Mitchell P.","family":"Wilson","sequence":"additional","affiliation":[{"name":"Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB T6G 2R3, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"S445","DOI":"10.1016\/j.jacr.2022.09.011","article-title":"ACR Appropriateness Criteria\u00ae Right Lower Quadrant Pain: 2022 Update","volume":"19","author":"Kambadakone","year":"2022","journal-title":"J. Am. Coll. Radiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"S373","DOI":"10.1016\/j.jacr.2018.09.033","article-title":"ACR Appropriateness Criteria\u00ae Right Lower Quadrant Pain-Suspected Appendicitis","volume":"15","author":"Garcia","year":"2018","journal-title":"J. Am. Coll. Radiol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1177\/08465371241266568","article-title":"CAR\/CETARS\/CSAR Practice Guideline on Imaging the Adult Patient with Right Lower Quadrant Pain","volume":"76","author":"Chawla","year":"2025","journal-title":"Can. Assoc. Radiol. J."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"434","DOI":"10.1016\/j.jamcollsurg.2008.12.003","article-title":"Improving Diagnosis of Acute Appendicitis: Results of a Diagnostic Pathway with Stand-ard Use of Ultrasonography Followed by Selective Use of CT","volume":"208","author":"Poortman","year":"2009","journal-title":"J. Am. Coll. Surg."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"639","DOI":"10.2214\/AJR.19.22370","article-title":"Ultrasound and CT in the Diagnosis of Appendicitis: Accuracy With Consideration of Indeterminate Examinations According to STARD Guidelines","volume":"215","author":"Crocker","year":"2020","journal-title":"Am. J. Roentgenol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1016\/j.ajem.2013.12.052","article-title":"Ultrasound evaluation of appendicitis: Importance of the 3 \u00d7 2 table for outcome reporting","volume":"32","author":"Fedko","year":"2014","journal-title":"Am. J. Emerg. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"519","DOI":"10.2214\/AJR.14.12864","article-title":"JOURNAL CLUB: The Alvarado Score as a Method for Reducing the Number of CT Studies When Appendiceal Ultrasound Fails to Visualize the Appendix in Adults","volume":"204","author":"Jones","year":"2015","journal-title":"Am. J. Roentgenol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"467","DOI":"10.7326\/M18-0850","article-title":"PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation","volume":"169","author":"Tricco","year":"2018","journal-title":"Ann. Intern. Med."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"605","DOI":"10.1002\/jcu.23905","article-title":"Are Cases of Nonvisualized Appendix on Ultrasound Not Actually Appendicitis? Single-Center Results","volume":"53","year":"2025","journal-title":"J. Clin. Ultrasound"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e24","DOI":"10.1016\/j.diii.2011.12.008","article-title":"The diagnostic value of indirect ultrasound signs during acute adult appendicitis","volume":"93","author":"Konan","year":"2012","journal-title":"Diagn. Interv. Imaging"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1002\/jcu.22248","article-title":"Abdominal wall thickness is not useful to predict appendix visualization on sonography in adult patients with suspected appendicitis","volume":"43","author":"Koseekriniramol","year":"2015","journal-title":"J. Clin. Ultrasound"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"472","DOI":"10.1148\/radiol.2302021520","article-title":"Appendicitis: Evaluation of Sensitivity, Specificity, and Predictive Values of US, Doppler US, and Laboratory Findings","volume":"230","author":"Kessler","year":"2004","journal-title":"Radiology"},{"key":"ref_13","unstructured":"Brahm, G., and Ross, I. (December, January 26). The Nonvisualized Appendix on Ultrasound: What Does It Mean?. Proceedings of the Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, Chicago, IL, USA."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"290","DOI":"10.1097\/RUQ.0000000000000214","article-title":"When the Appendix Is Not Seen on Ultrasound for Right Lower Quadrant Pain: Does the Interpretation of Emergency Department Physicians Correlate with Diagnostic Performance?","volume":"32","author":"Ly","year":"2016","journal-title":"Ultrasound Q."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"889","DOI":"10.2214\/ajr.183.4.1830889","article-title":"The Nonvisualized Appendix: Incidence of Acute Appendicitis When Secondary Inflammatory Changes Are Absent","volume":"183","author":"Nikolaidis","year":"2004","journal-title":"Am. J. Roentgenol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"125","DOI":"10.4103\/JMU.JMU_139_21","article-title":"Effect of Alvarado Score on the Negative Predictive Value of Nondiagnostic Ultrasound for Acute Appendicitis","volume":"30","author":"Prapruttam","year":"2022","journal-title":"J. Med. Ultrasound"}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/2\/304\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T10:09:57Z","timestamp":1768817397000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/2\/304"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,17]]},"references-count":16,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["diagnostics16020304"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics16020304","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,17]]}}}