Outcomes for Children With a Nonvisualized Appendix on Ultrasound

Identification of children with a nondiagnostic ultrasound at a low appendicitis risk using a pediatric Appendicitis Risk Calculator

OBJECTIVES

Up to 50% of ultrasounds (USs) for suspected pediatric appendicitis are nondiagnostic. While the validated low-risk clinical pediatric Appendicitis Risk Calculator (pARC) score < 15% and the low-risk US with nonvisualized appendix and no periappendiceal inflammation carry relatively low appendicitis risks, the contribution of the combination of both characteristics to this risk has never been assessed. The primary objective was to determine the proportion of children with the low-risk US-low-risk pARC combination with appendicitis. We hypothesized that this proportion would be 2.5% (upper 95% CI ≤ 5%).

METHODS

A retrospective cohort study of 448 previously healthy children 4-17 years old at a pediatric ED with suspected appendicitis, nondiagnostic US, and persistent clinical concern about appendicitis. Two investigators abstracted demographic, clinical, and imaging data. Based on published criteria, USs were classified as low-risk or high-risk. The pARC includes seven demographic, clinical, and laboratory variables and is quantified according to the published formula. The primary outcome was appendicitis, based on the histological evidence. All nonoperated patients underwent a 1-month-follow-up to exclude delayed appendicitis diagnoses.

RESULTS

Sixty of the 448 (13.4%) patients had appendicitis; 269 (60%) had low-risk US, 262 (58.4%) had low-risk pARC, and 163 (36.4%) had both characteristics. The appendicitis rates with low-risk pARC alone and low-risk US alone were 14/262 (5.4%) and 21/269 (7.8%), respectively. A total of 2/163 children (1.2%) with low-risk pARC and low-risk US had appendicitis (95% CI 0%-4.4%). Higher-risk US increased the appendicitis odds 5 (95% CI 1.54-20.55) to 11 times (95% CI 2.41-51.10) across pARC levels. The low-risk combination had sensitivity of 96.7% (95% CI 88.5%-99.6%), specificity of 41.5%, positive predictive value of 20.4%, and negative predictive value of 98.8% (95% CI 95.6%-99.9%).

CONCLUSIONS

The children with low-risk pARC and low-risk US combination are unlikely to have appendicitis and can be discharged home. The presence of higher-risk US-pARC score combinations substantially increases the appendicitis risk and warrants reassessment or interval imaging.

Finding Waldo: Sonographic systematic approach to localize the appendix in children

OBJECTIVES

To describe a systematic scanning approach using anatomical landmarks followed by an assessment of radiology trainees' ability to identify the normal appendix in healthy children.

METHODS

Uncontrolled pre and post study assessing radiology residents' sonographic skills in detecting the normal appendix in healthy children. Initial questionnaire for the trainees' demographics, perceptions and experiences in detecting the appendix with ultrasound in children followed by a precourse test on healthy volunteers. Hands-on training was conducted by describing a systematic sonographic approach to identify the appendix using anatomical landmarks, and then a postcourse test was carried out. The primary outcome was unprompted ability to identify the appendix. Subjective self-scoring of confidence was also recorded.

RESULTS

A three-hour hands-on workshop was conducted. Sixteen radiology trainees participated and were randomly distributed to four stations, each with different ultrasound machines and healthy volunteers. Fifteen had a precourse assessment, and 12 completed the postcourse assessment. Before the course, 3/15 (20%) identified the appendix, while 10/12 (83%) identified the appendix afterward. After the course, participants perceived finding the appendix easier than before. There was no statistically significant difference in the participants' perceived confidence in detecting the appendix.

CONCLUSIONS

With the described scanning technique, most of the participants were able to identify the normal appendix after receiving short hands-on training. This highlights the importance of targeted training of radiology trainees and nonradiologists.

Characterization and quantification of fluid in the abdomen by ultrasound and magnetic resonance imaging in children with clinical suspicion of appendicitis

PURPOSE

While regarded as a secondary sign of pediatric appendicitis, the frequency of physiologic intra-abdominal fluid in children with suspected but absent appendicitis is unknown. Ex vivo: to assess the validity of US/MRI measurements of free fluid. In vivo: in suspected pediatric appendicitis, to assess the amount of abdominal fluid by US and MRI, determine performance characteristics of US in fluid detection and identify fluid volume ranges in confirmed appendicitis.

METHODS

Ex vivo: criterion validity of US and MRI for fluid volume measurements was tested using tissue-mimicking phantoms filled with different volumes of distilled water. In vivo: all participants from a previous prospective study of suspected appendicitis were evaluated by US; MRI was performed after equivocal USs. Qualitative and quantitative analyses of abdominal fluid and correlation of fluid presence with appendicitis were performed.

RESULTS

Ex vivo: no difference was found between phantom-fluid amount and measured volume using the formula for volume of an ellipsoid for US (P=0.19) or MRI (P=0.08). In vivo: intra-abdominal fluid was present in 212/591 (35.9%) patients; 75/212 patients with fluid (35.4%) had appendicitis, 60 (28.3%) had alternate diagnoses, and 77 (36.3%) had physiologic fluid. Sensitivity and specificity of US for fluid detection were 84% (95% CI 71-93) and 65% (95% CI 52-77), respectively. In children with versus without appendicitis, the respective ranges of fluid volume were 0.7-1148.8 ml and 0.8-318 ml.

CONCLUSION

The volume of an ellipsoid formula is a valid method for quantifying intra-abdominal fluid. The sole presence of intra-abdominal fluid on US does not support the diagnosis of pediatric appendicitis.

Predictive Factors of Acute Appendicitis in Children With Non-Visualized Appendix on Ultrasound: A Prospective Cohort Study

Background: Most studies have demonstrated the high accuracy of ultrasound for the diagnosis of acute appendicitis (AA) in children. However, the lack of visualization of the appendix on ultrasound is usually a challenge. The aim of this study was to identify any factors that might help the physician make the right decision when dealing with a child with suspected appendicitis and an appendix not seen on ultrasound. Patients and Methods: After receiving Institutional Review Board approval, we conducted a prospective study in a pediatric emergency department from January 1, 2022, to December 31, 2022. All children under 14 years of age with suspected AA and an appendix not visualized on ultrasound were included. Results: During the study period, 333 children presented with suspected AA. Of these patients, 106 had an appendix not seen on ultrasound. Our patients' median age was 10 years (interquartile range [IQR], 8-11 years), with 54.7% (n = 58) of children being female. Twenty-five (23.6%) were ultimately diagnosed with AA based on pathologic examination. Multivariable logistic regression analysis revealed that Alvarado score ≥6 and increased peri-appendiceal fat echogenicity were predictive for AA. The combination of these two factors provided a positive predictive value of 100%. A white blood cell (WBC) count ≤10 × 109/L and/or a C-reactive protein (CRP) level ≤6 mg/L makes the diagnosis of appendicitis unlikely. Conclusions: In conclusion, our study demonstrated that an Alvarado score at or above six and increased peri-appendiceal fat echogenicity are independent predictive factors of AA in children with non-visualized appendix on ultrasound. The combination of these two factors would confirm the diagnosis of AA in these patients.

Single institutional experience with initial ultrasound followed by computed tomography or magnetic resonance imaging for acute appendicitis in adults

PURPOSE

The objectives of this study was to assess the performance of ultrasound (US) for suspected appendicitis in adult patients and to evaluated the additive value of short-interval (within 1 week) computed tomography (CT) or Magnetic Resonance Imaging (MRI) after performing an initial US.

METHODS

In this IRB-approved, HIPAA-compliant, retrospective study, electronic medical records (EMRs) were queried for "US appendicitis" performed over a 2-year interval. EMR was reviewed for CT or MRI performed within 1 week of this exam, and if any new or additional information was available at subsequent exam. White count, patient disposition, and pathology, if surgery was performed, were also recorded.

RESULTS

682 patients underwent US for appendicitis over a 2-year duration, age range from 18 to 92 years (average: 30.1 years, M:F = 141:541). Findings showed 126/682 patients with normal appendix, 75/682 uncomplicated appendicitis, and 4/682 with complicated appendicitis. When performed, no additional findings were seen in these groups on short-interval CT or MRI. 2/682 patients had equivocal findings on US but eventually had normal appendix identified on CT. Four hundred and seventy-three patients had non-visualized appendix, of which only 14/473 (3.1%) eventually had appendicitis.

CONCLUSIONS

Ultrasound is an effective initial modality for evaluating appendicitis even in adult patients. Once a normal appendix, uncomplicated or complicated appendicitis is identified on US, no further imaging is necessary. Very few patients with non-visualization of the appendix eventually have appendicitis. Hence, these patients can be managed with active clinical follow-up rather than immediate CT or MRI. Symptoms and clinical scoring systems can be used for triage of these patients.