Application value of abdominal ultrasonography in the diagnosis of pediatric patients aged 3-12 years with acute appendicitis

Abstract

BACKGROUND

Early detection of acute appendicitis (AA) in pediatric cases, critical to avoiding life-threatening complications such as perforation or abscess, remains challenging.

AIM

To evaluate the utility of abdominal ultrasonography (AUS) in diagnosing pediatric AA.

METHODS

Overall, 102 pediatric patients (aged 3-12 years) suspected of having AA were enrolled and divided into the AA (n = 78) and non-AA (n = 24) groups. All children underwent AUS and computed tomography (CT). Comparative analyses regarding general patient characteristics and appendix-specific parameters were conducted. The diagnostic performance of AUS and CT in pediatric AA was evaluated.

RESULTS

All appendix-related parameters were greater in the AA group than in the non-AA group. The areas under the receiver-operating characteristic curves for pediatric AA diagnosis using AUS, CT, and AUS + CT were 0.870, 0.824, and 0.931 (all P < 0.001), respectively (AUS: 94.87% sensitivity, 79.17% specificity; CT: 89.74% sensitivity, 75.00% specificity; combined: 98.72% sensitivity, 87.50% specificity). The positive predictive value (PPV), negative predictive value (NPV), accuracy rate, positive detection rate, and misdiagnosis rate of AUS were 93.67%, 82.61%, 91.18%, 72.55%, and 20.83%, respectively. CT had a slightly lower PPV (92.11%) and NPV (69.23%), along with accuracy, positive detection, and misdiagnosis rates of 86.27%, 68.63%, and 25%, respectively. Their combination improved performance, yielding 96.25% PPV, 95.45% NPV, 96.08% accuracy, 75.49% positive detection rate, and 12.50% misdiagnosis rate.

CONCLUSION

AUS demonstrates certain diagnostic potential in AA diagnosis in pediatric patients, and its combination with CT further improves diagnostic efficacy.

Key Words: Abdominal ultrasonography; Pediatric acute appendicitis; Diagnosis; Clinical application value

Core Tip: Comparative research regarding the diagnostic effectiveness of abdominal ultrasonography (AUS) vs computed tomography (CT) for pediatric acute appendicitis (AA) remains limited. This study involved 102 children aged 3-12 years suspected of AA to compare their clinical utility based on appendiceal characteristics and diagnostic performance. The results confirmed notable abnormalities in appendix-related parameters among patients with AA. AUS showed diagnostic potential for pediatric cases, and the accuracy increased when it was combined with CT. These findings highlight a pathway (AUS + CT) to more accurate diagnoses, reduced surgical overtreatment, and efficient resource use.

INTRODUCTION

Acute appendicitis (AA) is among the most prevalent abdominal ailments requiring emergent surgery globally, with a predilection for the pediatric population (12.93% of all AA cases). Clinically, it may manifest as fever, gastrointestinal disorders, diffuse abdominal pain, diffuse abdominal tenderness, etc.[1,2]. Epidemiological statistics have revealed a lifetime appendicitis risk of 8.6% in men and 6.7% in women. In the United Kingdom alone, it leads to 72000 hospitalizations annually[3,4]. The exact etiology of AA is intricate and potentially involves factors such as high sugar consumption, low dietary fiber intake, and viral, bacterial, and parasitic infections[5]. Diagnosing AA in pediatric patients is a challenging and arduous task, primarily due to the often manifestations of nontypical symptoms[6,7]. However, the early detection of AA in children is of utmost significance for averting severe sequelae, such as appendiceal perforation and abscess formation[8]. Thus, this study aimed to delve deeply into the early diagnosis of pediatric AA to contribute to the improvement of the diagnostic efficiency of early detection and prevention of serious events such as perforation and abscess.

Both abdominal ultrasonography (AUS) and computed tomography (CT) are integral imaging modalities in the diagnostic algorithm for AA, as they not only contribute to enhancing diagnostic accuracy but also aid in improving patient prognosis[9]. AUS has favorable attributes. It is noninvasive, pain-free, and non-ionizing, entailing a relatively low cost. The procedure is also easy to perform and is renowned for its high safety profile and diagnostic accuracy. During the diagnosis, a color Doppler ultrasound system is used to conduct a sonographic assessment of the patient’s abdomen, allowing for the collection of pathological data such as appendix-related parameters and inflammation status[10,11]. Moreover, this imaging technique can be applied to patients with abnormal physical signs, thus facilitating more efficient diagnosis, particularly for children and the elderly, who often experience diagnostic delays[12,13]. In a meta-analysis, Cho and Oh[14] reported an overall pooled sensitivity of 81% and specificity of 87% of ultrasound for AA diagnosis. Conversely, although CT is highly esteemed for its diagnostic value, it is associated with potential exposure to ionizing radiation, which restricts its widespread use[15]. Nevertheless, CT holds certain advantages over AUS. For example, it exhibits reduced operator dependence, allowing for more consistent visualization of the appendix, even in anatomically challenging locations, such as the retrocecal region or other aberrant positions. Furthermore, in patients with complications, such as abscess formation or perforated appendicitis, CT is better equipped to delineate the disease extent and nature, providing comprehensive information that is invaluable for treatment planning[16]. In a retrospective analysis, the CT-based decision-tree algorithm showed high diagnostic accuracy for pediatric complicated appendicitis [area under the curve (AUC) = 0.91], with 91.8% sensitivity and 90.0% specificity[17].

This study analyzed the clinical application value of AUS in the diagnosis of pediatric AA. Additionally, it evaluated the clinical utility of CT and the combined application of AUS and CT in the diagnosis of this pediatric condition. The findings of this study hold significant clinical implications for optimizing the early diagnosis of pediatric patients with suspected AA. No comparative studies have focused on the diagnostic performance of AUS and CT in pediatric AA. Thus, this study was conducted to fill this gap, with implications for enhancing diagnostic reliability, preventing unnecessary operations, and refining healthcare resource distribution.

MATERIALS AND METHODS

General information

This study has obtained approval from the Ethics Committee of First People’s Hospital of Jiashan County. Initially, 102 pediatric patients (aged 3-12 years) suspected of AA and admitted to The First People’s Hospital of Jiashan County between August 2022 and August 2024 were enrolled. These children were categorized into the AA (n = 78) and non-AA (n = 24) groups. All the pediatric patients underwent comprehensive diagnostic evaluations, including AUS and CT. Statistical analysis revealed no significant difference in general characteristics between the two groups (P > 0.05), validating their clinical comparability.

Sample size determination

The sample size was calculated using a standard diagnostic test formula. The input parameters were as follows: π = 0.85 (expected sensitivity), π₁ = 0.75 (lower threshold), Z_a/2 = 1.96 (α = 0.05, two-tailed), and Z_β = 0.84 (β = 0.20, 80% power). The initial calculation required 61 participants. Considering a 20% dropout rate, the final sample size increased to 76. The AA group comprised 78 cases, satisfying this requirement. Although the non-AA group was limited to 24, this remains adequate for preliminary specificity evaluation, given that diagnostic tests mainly assess sensitivity in the AA (disease) group, with controls serving primarily for specificity calculations. Statistical power was calculated based on available data (AA group, n = 78; non-AA group, n = 24). In the AA group, the sensitivity was 83.3% (65/78), with exact binomial testing indicating > 90% power, significantly higher than the predetermined 80% threshold. For the non-AA group, the specificity was 75.0% (18/24), with the 95% confidence interval (95%CI: 54%-90%) calculated using the Clopper-Pearson method remaining within acceptable limits despite sample size constraints.

Inclusion and exclusion criteria

Inclusion criteria: (1) All pediatric patients must meet the diagnostic criteria for AA[18]; (2) Patients must be between 3 and 12 years old; (3) Patients must present with symptoms such as leukocytosis of varying degrees, fever, and right-lower-quadrant abdominal pain; and (4) Complete clinical data are available for each patient.

Exclusion criteria: (1) Severe malnutrition; (2) Comorbid autoimmune connective tissue diseases or pulmonary infections; (3) Abscesses surrounding the appendix; (4) Chronic appendicitis; (5) Impaired cardiac, pulmonary, or renal functions, as well as severe hematological disorders; and (6) Other acute abdominal emergencies.

Examination protocols

All pediatric patients underwent both AUS and CT. For AUS, an ultrasonic diagnostic apparatus was employed. The examination incorporated a strategic combination of convex- and linear-array probes, with the probe frequency set within 3.5-12 MHz. Highly experienced clinicians, with extensive expertise in pediatric AUS, interpreted the ultrasound findings. The diagnostic criteria were as follows: (1) Ultrasonographic evidence indicated that the maximum diameter of the appendix was > 6 mm, and the appendiceal wall thickness was > 2 mm; and (2) AUS detected either prominent intraluminal fluid accumulation in the appendiceal lumen or the presence of appendiceal fecaliths encased by surrounding tissues. Following the diagnostic procedures, surgical interventions were promptly initiated in both groups. Rigorous comparison was then conducted between the surgical findings and preoperative clinical diagnoses.

For CT, a 64-slice helical CT system was utilized for imaging. Pediatric patients were positioned supine, ensuring optimal anatomical alignment for comprehensive abdominal scanning. The scanning coverage of the entire abdomen spanned from the superior margin of the diaphragm to the pubic symphysis. All participants underwent both non-contrast (plain) and contrast-enhanced CT. The parameters were set as follows: Pitch, 1; slice interval, 0.5 mm; reconstruction slice thickness, 1 mm; collimation, 0.6 mm; tube current, 200 mA; and tube voltage, 120 kV. To improve the visualization of the gastrointestinal tract and adjacent structures, children were instructed to consume appropriate volumes of water at specific time intervals before the scan. Specifically, water intake was scheduled at 2, 1, and 0.5 hour before the scan. For the contrast-enhanced scan, 10 mL of iopromide, a commonly used iodinated contrast agent, was administered via the cubital vein using a high-pressure injector at a constant flow rate of 3 mL/s. After the injection, scanning was initiated with a 60-second delay. Subsequently, highly experienced radiologists analyzed the acquired CT images. Initially, the appendix was observed on the transverse plane. The CT data were then processed at a dedicated workstation, where multiplanar reconstructions in the sagittal, coronal, and curved planar formats were performed. Finally, the maximum diameter of the appendix, maximum thickness of the appendiceal wall, and maximum extent of transmural edema were measured.

De-identified imaging data were analyzed separately by two senior radiologists (one specializing in ultrasound for ≥ 5 years and the other in CT for ≥ 5 years), who had no knowledge of one another’s assessments or patient backgrounds. When diagnostic interpretations conflicted (e.g., positive ultrasound but negative CT), a third experienced physician adjudicated the final diagnosis based on majority consensus. Good interobserver consistency was observed (κ = 0.78, 95%CI: 0.65-0.91), and intraobserver stability was confirmed (interclass correlation coefficient = 0.85, 95%CI: 0.73-0.93).

Analytical indicators

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, positive detection rate, and misdiagnosis rates of AA in the two groups were analyzed.

Statistical analysis

Statistical analysis was conducted using the IBM SPSS Statistics version 24.0 (IBM Corp., Armonk, NY, United States). For measurement data, they were statistically described using the mean ± SE of the mean. Measurement data were compared between the two groups using the t-test. Count data were described using frequencies (percentages). The χ² test was utilized to evaluate the differences in the distribution of these categorical variables between the groups. A significance level of P < 0.05 was adopted as the threshold for significance.

RESULTS

General data between the two groups

The male-to-female ratios were 1.60:1 and 1.67:1 and the mean ages were 7.73 ± 2.45 years and 7.42 ± 2.84 years in the AA and non-AA groups, respectively. The time from disease onset to hospital admission was 10.26 ± 3.88 hours in the AA group and 9.67 ± 3.46 hours in the non-AA group. Further details are presented in Table 1. No significant differences were found in variables such as sex, age, time from disease onset to hospital admission, single-parent family, and family medical history between the two groups (P > 0.05, Table 1).

Table 1 Comparative analysis of general data between the two pediatric patient groups.

Indicators	AA group (n = 78)	Non-AA group (n = 24)	χ2/t	P value
Gender (male/female)	48/30	15/9	0.007	0.932
Age (years)	7.73 ± 2.45	7.42 ± 2.84	0.522	0.603
Time from disease onset to hospital admission (hour)	10.26 ± 3.88	9.67 ± 3.46	0.667	0.506
Single-parent family (no/yes)	63/15	19/5	1.961	0.161
Family medical history (without/with)	70/8	20/4	0.726	0.394

AA: Acute appendicitis.

Appendix-related parameters between the two groups

The maximum diameter of the appendix, maximum thickness of the appendiceal wall, and maximum extent of transmural edema were significantly greater in the AA group than in the non-AA group (all P < 0.05; Figure 1).

Figure 1 Comparative analysis of appendix-related parameters between the two pediatric patient groups. A: The maximum diameter of the appendix of the two pediatric patient groups; B: The maximum thickness of the appendiceal wall of the two pediatric patient groups; C: The maximum extent of transmural oedema of the two pediatric patient groups. ^aP < 0.01 vs the non-acute appendicitis group; ^bP < 0.001 vs the non-acute appendicitis group.

Detection results of AUS, CT, and their combined application

Of the total cases, histopathology (gold standard) identified 78 positive cases (76.47%) compared with 79 (77.45%) via AUS, 76 (74.51%) via CT, and 80 (78.43%) via AUS + CT. Detailed information can be found in Tables 2, 3 and 4.

Table 2 Analysis of detection results of abdominal ultrasonography.

Abdominal ultrasonography	Gold standard		Total
	Positive	Negative
Positive	74	5	79
Negative	4	19	23
Total	78	24	102

Histopathological examination serves as the gold standard.

Table 3 Analysis of detection results of computed tomography examination.

CT examination	Gold standard		Total
	Positive	Negative
Positive	70	6	76
Negative	8	18	26
Total	78	24	102

The gold standard is histopathological examination. CT: Computed tomography.

Table 4 Analysis of detection results of the combined detection.

Combined detection	Gold standard		Total
	Positive	Negative
Positive	77	3	80
Negative	1	21	22
Total	78	24	102

Histopathological examination is the gold standard.

Diagnostic performance of AUS, CT, and their combined application

An evaluation of diagnostic accuracy using receiver operating characteristic (ROC) curves indicated that AUS (AUC = 0.870), CT (AUC = 0.824), and their combination (AUC = 0.931) were all significant in detecting pediatric AA (P < 0.001). Individually, AUS exhibited the highest sensitivity (94.87%) while demonstrating favorable specificity (79.17%). The combined approach had further improved specificity (87.50%) and sensitivity (98.72%). A visual representation of these findings and additional details are provided in Figure 2 and Table 5, respectively.

Figure 2 Receiver operating characteristic curves of abdominal ultrasonography, computed tomography examination, and their combined detection for pediatric acute appendicitis. AUC: Area under the curve; CT: Computed tomography.

Table 5 Diagnostic efficacy of abdominal ultrasonography, computed tomography examination, and their combined detection for pediatric acute appendicitis.

Inspection method	AUC	95%CI	Specificity (%)	Sensitivity (%)	P value
Abdominal ultrasonography	0.870	0.770-0.971	79.17	94.87	< 0.001
CT examination	0.824	0.714-0.933	75.00	89.74	< 0.001
Combined detection	0.931	0.852-1.011	87.50	98.72	< 0.001

CT: Computed tomography; AUC: Area under the curve; 95%CI: 95% confidence interval.

Relevant parameters of AUS, CT, and their combined modalities

For pediatric AA screening, the diagnostic accuracy rates were 91.18% with AUS, 86.27% with CT, and 96.08% when both methods were combined. Further details are provided in Table 6.

Table 6 Analysis of relevant parameters of abdominal ultrasonography, computed tomography, and their combined modalities (%).

Inspection method	Positive predictive value	Negative predictive value	Accuracy	Positive detection rate	Misdiagnosis rate
Abdominal ultrasonography	93.67	82.61	91.18	72.55	20.83
CT examination	92.11	69.23	86.27	68.63	25.00
Combined detection	96.25	95.45	96.08	75.49	12.50

CT: Computed tomography.

DISCUSSION

In pediatric patients with AA, the anatomical characteristics of the appendix, namely, its narrow lumen, thin walls, and abundant lymphoid tissue, render it highly susceptible to adverse events. Specifically, complications such as perforation, ischemia, and necrosis can readily occur at disease onset[19]. Thus, prompt diagnosis, along with appropriate treatment interventions, is pivotal in mitigating the risk of these complications, particularly perforation, in pediatric patients with AA[20]. This study focuses on the early diagnosis of pediatric patients with AA to provide reliable references and novel insights into their diagnosis and treatment.

AUS, often serving as the primary diagnostic modality, presents distinct advantages when applied to pediatric patients. This finding is attributed to the characteristic physiological features of pediatric patients, including reduced abdominal adiposity and a relatively slender body habitus[21]. The cost-effective and real-time imaging functionality of this technique enables the precise visualization and capture of internal organ structures and their dynamic movements[22]. Conversely, CT assesses the condition primarily through indirect signs such as fluid effusion in the periappendiceal space, presence of free gas, and increased density in the abdominal wall adipose tissue[23]. Additionally, with its high-sensitivity detectors and precisely collimated X-ray beams, cross-sectional scans can be obtained from the level of the second lumbar vertebra down to the pelvic region in pediatric patients with AA, allowing for the acquisition of highly detailed and sharp images of both superficial and deep soft tissues[24]. In this study, 78 pediatric patients with AA and 24 without it were pathologically confirmed. For AUS in screening pediatric AA, the specificity, sensitivity, and accuracy rates were 79.17%, 94.87%, and 91.18%, respectively. Thus, although the sensitivity of AUS demands enhancement, it does present certain clinical merits in terms of high specificity and accuracy. This situation can, to a certain extent, be ascribed to the substantial influence of operators’ subjective biases and clinical expertise on the AUS results, which may give rise to variances in diagnostic performance among operators[25]. Hamid et al[26] noted that the visualization of the appendix via AUS significantly increased the probability of accurately diagnosing appendicitis, implying that the relatively high diagnostic accuracy of AUS might be attributed to the successful visualization of the appendix. The results indicated that compared with the non-AA group, the AA group exhibited a larger maximum diameter of the appendix, maximum thickness of the appendiceal wall, and maximum extent of transmural edema. This demonstrates that CT allows for the accurate observation of alterations in various appendiceal parameters, thus facilitating effective diagnostic decision-making by operators. To some degree, this can be attributed to the high resolution of CT, which can comprehensively reveal both the direct and indirect manifestations of AA in pediatric patients, accurately locate the appendix, and help effectively identify the source of appendiceal abscesses[27]. Although CT is highly valuable for diagnosis, its radiation exposure in pediatric patients raises concerns about long-term effects such as cancer. A potential solution may stem from integrating deep learning with low-dose CT to minimize these risks[28].

In the ROC analysis, the AUCs for AUS and CT in diagnosing pediatric AA were 0.870 and 0.824, respectively. Notably, when utilized in combination, the AUC could increase to 0.931. Specifically, AUS exhibited a high specificity of 79.17% while achieving a considerable sensitivity of 94.87%. Through method combination (CT + AUS), specificity was further improved to 98.72%. Compared with CT, AUS demonstrated relatively higher PPV, NPV, and positive detection rates, which were 93.67%, 82.61%, and 72.55%, respectively. Moreover, the misdiagnosis rate of AUS was relatively low (20.83%). The combined diagnostic strategy demonstrated superiority based on a PPV of 96.25%, NPV of 95.45%, accuracy of 96.08%, and positive detection rate of 75.49%. In the report by Pedram et al[29], the AUC for AUS in diagnosing pediatric AA was 0.853, which is close to the result (0.870) obtained in the present study. In the meta-analysis conducted by Al-Khayal and Al-Omran[30], the specificity, sensitivity, accuracy, and PPV of AUS in screening for AA were 95.9%, 83.7%, 92.9%, and 89.8%, respectively, which align well with our observations. In this study, CT demonstrated the highest misdiagnosis rate, reaching 25.00%. This phenomenon can, to a certain degree, be ascribed to the immature development of the nervous systems of pediatric patients with AA, who are typically young. Owing to this immaturity, they are unable to precisely articulate the specific location and intensity of pain. Consequently, providing physicians with the necessary and accurate information becomes arduous for them, thereby increasing the probability of misdiagnosis[31]. This may also be related to the relatively high mobility of the pediatric gastrointestinal tract, which poses challenges for physicians during physical examinations[32].

This study has certain limitations, including a small sample size and the single-center setting. Subsequent investigations should adopt a multicenter approach to recruit a larger non-AA cohort with age- and sex-matched controls to strengthen the validity and generalizability of the results. Additionally, the diagnostic performance of AUS is operator-dependent. Despite good inter-rater reliability (κ = 0.78), results may differ for less experienced doctors. Future studies should examine how AUS performs across different experience levels to determine its true clinical utility. Finally, the retrospective design is associated with a risk of selection bias (e.g., the exclusion of low-quality images), which may overestimate sensitivity. Conducting prospective studies may improve the control over operational variables.

CONCLUSION

In summary, AUS demonstrates potential clinical utility in the diagnosis of pediatric AA, effectively aiding in the early diagnosis of affected children. Notwithstanding, to maximize diagnostic accuracy, implementing a comprehensive diagnostic protocol that combines AUS with CT is highly advisable. This combined approach may significantly enhance diagnostic performance across multiple dimensions, such as diagnostic efficiency, sensitivity, specificity, and overall accuracy, thus providing robust support for early-stage clinical interventions and ultimately contributing to improved patient outcomes.