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Predictive values of indirect ultrasound signs for low risk of acute appendicitis in paediatric patients without visualisation of the appendix on ultrasound
  1. Juan Pernía1,
  2. Teresa Cancho1,
  3. Inés Segovia1,
  4. Pilar de Ponga2,
  5. Elena Granda1,
  6. Roberto Velasco3,4
  1. 1Pediatrics Department, Hospital Universitario Rio Hortega, Valladolid, Spain
  2. 2Servicio Cántabro de Salud, Santander, Cantabria, Spain
  3. 3Pediatric Emergency Unit, Parc Taulí Hospital Universitari. Institut d'Investigacio i Innovacio Parc Tauli (I3PT-CERCA), Universitat Autònoma de Barcelona, Sabadell, Catalunya, Spain
  4. 4Paediatrics & Child Health, University College Cork, Cork, Ireland
  1. Correspondence to Dr Roberto Velasco, Minority Diseases, Institut d'Investigacio i Innovacio Parc Tauli, Sabadell, Catalunya, Spain; robertovelascozuniga{at}


Background and objectives The ability to rule appendicitis in or out using ultrasound is limited by studies where the appendix is not visualised. We determined whether the absence of indirect ultrasound signs can rule out appendicitis in children undergoing a radiology-performed ultrasound in which the appendix is not visualised

Methods This was a single-centre retrospective observational study of patients aged 3–13 with a clinical suspicion of acute appendicitis evaluated in a Paediatric Emergency Department in Spain from 1 January 2013 to 31 December 2019. For those patients who had formal ultrasound, direct and indirect findings of ultrasound were abstracted from the ultrasound report. The surgical pathology report was established as the gold standard in patients who underwent an appendectomy. In those who did not, appendicitis was considered not to be present if there was no evidence in their charts that they had undergone an appendectomy or conservative therapy for appendicitis during the episode. The main outcome variable was the diagnosis of acute appendicitis. For patients undergoing ultrasound, the independent association of each indirect ultrasound sign with the diagnosis of appendicitis in patients without a visualised appendix was analysed using logistic regression.

Results We included 1756 encounters from 1609 different episodes. Median age at the first visit of each episode was 10.1 years (IQR, 7.7–11.9) and 921 (57.2%) patients were men. There were 730 (41.6%) encounters with an Alvarado score ≤3, 695 (39.6%) with a score 4–6 and 331 (18.9%) with a score ≥7. Appendicitis was diagnosed in 293 (17.8%) episodes. Ultrasonography was performed in 1115 (61.6%) encounters, with a visualised appendix in 592 (53.1%).

The ultrasound findings independently associated with appendicitis in patients without a visualised appendix were the presence of free intra-abdominal fluid in a small quantity (OR:5.0 (95% CI 1.7 to 14.6)) or in an abundant quantity (OR:30.9 (95% CI 3.8 to 252.7)) and inflammation of the peri-appendiceal fat (OR:7.2 (95% CI 1.4 to 38.0)). The absence of free fluid and inflammation of the peri-appendiceal fat ruled out acute appendicitis in patients with an Alvarado score <7 with a sensitivity of 84.6% (95% CI 57.8 to 95.7) and a negative predictive value of 99.4% (95% CI 97.8 to 99.8).

Conclusions Patients with an Alvarado score <7 and without a visualised appendix on ultrasound but who lack free fluid and inflammation of the peri-appendiceal fat are at very low risk of acute appendicitis.

  • pediatric emergency medicine
  • ultrasonography
  • Observational Study
  • Diagnostic Techniques and Procedures

Data availability statement

Data are available upon reasonable request.

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  • Handling editor DARRYL WOOD

  • X @egranda15, @RoberVelasco80

  • Contributors RV designed the study, analysed the data, wrote the initial draft of the manuscript and approved the final manuscript as submitted. JP conceptualised and designed the study, collaborated in data collection, revised multiple drafts of the manuscript and critically revised the final submitted manuscript. TC, IS, PdP and EG collaborated in the design of the study and in data collection, revised multiple manuscript drafts and critically revised the final submitted manuscript. All authors approved the final manuscript as submitted and agreed to be accountable for all aspects of the work. RV acts as guarantor, and accepts full responsibility for the finished work and the conduct of the study, had access to the data and controlled the decision to publish.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer-reviewed.