AAP Paper
The non-diagnostic ultrasound in appendicitis: is a non-visualized appendix the same as a negative study?

https://doi.org/10.1016/j.jpedsurg.2015.03.012Get rights and content

Abstract

Purpose

The purpose of this retrospective study was to investigate outcomes in children who underwent a non-diagnostic ultrasound (US) evaluating for appendicitis and to identify predictors of a negative diagnosis.

Methods

An IRB-approved retrospective chart review was performed on patients age 0–18, who underwent an abdominal US evaluating for acute appendicitis from 2004 through 2013. Clinical data and specified outcomes were recorded, and exams were categorized into non-diagnostic studies and further separated into studies where the appendix was non-visualized.

Results

Of the 1383 studies included for analysis, 876 were non-diagnostic for acute appendicitis (63.34%) with 777 specifically because the appendix was non-visualized. Seven hundred forty of the 876 non-diagnostic studies and 671 of the 777 non-visualized studies were ultimately considered true negatives, corresponding to a negative predictive value (NPV) of 84.47 and 86.36%, respectively. In patients with WBC < 7.5 × 109/L, the NPV of non-diagnostic and non-visualized studies increased to 97.12 and 98.86%, respectively. Patients with WBC < 11.0 × 109/L have similarly high NPVs of 95.59 and 96.99% (non-diagnostic and non-visualized).

Conclusion

Based on the high NPV of a non-diagnostic US in children without leukocytosis, these patients may safely avoid further diagnostic imaging for the workup of suspected appendicitis.

Section snippets

US technique and diagnostic criteria

Following voiding, a linear 12-5 transducer was used (linear 9-3, and/or curvilinear 9-4, 5-2 or 5-1 MHz for obese patients) for evaluation of the right lower quadrant in transverse and sagittal directions using a graded compression technique to search for the appendix. A positive study was reported upon identification of a blind-ending, tubular, non-compressible structure in the right lower quadrant measuring > 6.5 mm in diameter and showing connection to the cecum. Other signs indicating towards

Ultrasound results

A total of 1383 ultrasounds were performed on 1260 patients in order to evaluate for appendicitis. Two hundred one studies were positive (14.53%), 83 studies were suspicious as described in Section 1.3 (6.00%), 17 studies had low-suspicion (1.23%), 152 studies were negative (10.99%) and 54 studies were positive for an alternative diagnosis (3.90%). The remaining 876 studies were non-diagnostic for acute appendicitis (63.34%). This percentage was slightly higher than the 56–61% that was reported

Discussion

Despite appendicitis being the most common abdominal emergency in the world [1], its diagnosis remains problematic. The most immediate diagnostic tool has always been a skillfully executed history and physical exam. Unfortunately, clinical variations in presenting symptoms, difficulties interpreting the history and physical, non-specific signs and symptoms, and competing differential diagnoses all limit the efficacy of clinical reasoning [5]. A number of scoring systems have been developed to

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