Acute appendicitis is the most common surgical emergency in children, and laparoscopic appendectomy is its standard treatment. Although intraoperative adverse events (iAEs) are recognized as an important determinant of surgical safety and outcome, no validated tool exists for grading them in children. ClassIntra, an internationally validated five-level severity classification of intraoperative adverse events, has been validated in adults. Its use in children is limited to two single-centre cohorts - one in pediatric neurosurgery and one in a mixed pediatric robotic surgery programme - in which it was applied prospectively by the operating teams. Its inter-rater reliability has never been assessed in a pediatric population, it has not been applied to video-recorded pediatric procedures, and no study has focused on pediatric appendectomy. Likewise, the association between intraoperatively graded event severity and postoperative complication severity graded with the pediatric-specific Clavien-Madadi classification has not been examined in children. This prospective, single-center, single-surgeon, video-based pilot study (IDEAL Framework Stage 2a) evaluates whether ClassIntra can be feasibly applied to the laparoscopic phase of pediatric appendectomy. Eighty children aged 5 to under 18 years undergoing laparoscopic appendectomy for non-complicated acute appendicitis will be enrolled. Operative videos will be recorded, de-identified, assigned a case code, and independently assessed in randomized order by two pediatric surgeons from outside the operating institution, who remain blinded to all postoperative clinical data. Each observed event is characterized on three levels: event type (E1-E7), mechanism (GERT categories M1-M4), and severity (ClassIntra Grade I-V). Postoperative complications within 30 days are graded separately with the Clavien-Madadi classification by the principal investigator, independently of the video assessment. The primary outcome is the feasibility of ClassIntra in this setting, evaluated as a progression-criteria profile rather than a composite rule, using three pre-specified criteria: inter-rater reliability (Gwet's AC1 \>= 0.60, the key indicator), applicable coverage (proportion of non-assessable cases \< 5%), and discriminative capacity (at least three of the five ClassIntra grades represented in the cohort). Secondary outcomes are descriptive: iAE incidence with Wilson score confidence intervals and the distribution of event types, mechanisms and severity grades. Exploratory hypotheses examine the association of intraoperative event severity with adherence to the institutional Enhanced Recovery After Surgery (ERAS) protocol, with time to medical readiness for discharge, and with Clavien-Madadi-graded postoperative complication severity. The study involves no additional intervention, investigational product, or extra procedure for the participating children; care follows institutional standards throughout. Its purpose is to provide feasibility evidence and calibration parameters for subsequent multicenter validation studies, not to establish the validity of the classification system itself.
Background and Rationale Systematic classification of intraoperative adverse events (iAEs) is a prerequisite for measuring surgical safety. In adults, ClassIntra (Dell-Kuster et al., 2020) grades intraoperative events on five severity levels (Grade I-V) and has been internationally validated. In children, no population-specific instrument exists and pediatric experience with ClassIntra is limited to a small number of reports: a neurosurgical pilot congress abstract (Drexler et al., 2022; n=21), a full-text prospective neurosurgical cohort from the same group (Middelkamp, Drexler et al., World Neurosurgery 2025; n=47), and a prospective multidisciplinary pediatric robotic surgery programme in which ClassIntra was recorded alongside Clavien-Dindo grading (Vinit et al., Annals of Surgery 2023; n=300, of which 83 digestive and 105 urological or gynaecological procedures). In none of these was ClassIntra applied to video recordings, in none was its inter-rater reliability assessed, and none focused on appendectomy. The iAE profile of pediatric laparoscopic appendectomy - the most common pediatric surgical procedure - has not been systematically documented. For postoperative complications, a pediatric-validated instrument does exist: the Clavien-Madadi classification (Madadi-Sanjani et al., 2023; ERNICA validation 2024). The relationship between intraoperative event severity and postoperative complication severity has not been studied in children. Design Prospective, single-center, single-surgeon, video-based pilot study, positioned at Stage 2a (Development) of the IDEAL Framework for surgical innovation. Single-arm observational cohort; no control group and no comparison arm. The principal investigator performs all operations and does not serve as a rater; the investigator acts only as arbiter in case of unresolved disagreement between raters. Video Assessment Protocol Operations are recorded in 1920x1080 H.264 MP4 format. Recordings are de-identified, assigned a case code (PA-XXX), and distributed to raters in randomized order. Two independent pediatric surgery specialists from outside the operating institution serve as raters; a third specialist is pre-designated as reserve. Raters have no access to postoperative clinical data, which prevents halo effects. Raters undergo a three-stage training program before assessment begins: theoretical training (2 weeks), calibration sessions (2 weeks), and certification; an inter-rater reliability threshold of 0.60 is targeted at first calibration, with an additional calibration round if not reached. The assessment window is deliberately restricted to the laparoscopic phase, from insertion of the laparoscope into the abdomen until its withdrawal. Skin incision, port placement, fascial closure and anesthesia-related events are outside the assessment window. This partial application of ClassIntra is a pre-specified scope decision made for reasons of pilot scope management and rater workload, and is reported as a limitation. The study is not a retrospective analysis of an existing video archive: all videos are obtained prospectively after ethics approval, in accordance with the study protocol. Three-Level Event Characterization Each identified intraoperative event is characterized on three levels: * Level 1, event type: E1 bleeding, E2 thermal injury, E3 avulsion, E4 serosal tear, E5 injury to adjacent organ, E6 detached clip, E7 spillage (pediatric adaptation after Sanmoto 2025). * Level 2, mechanism: GERT categories M1 excessive force/distance, M2 insufficient force/distance, M3 wrong orientation, M4 insufficient visualization (Bonrath 2013), a procedure-independent internationally validated framework. * Level 3, severity: ClassIntra Grade I-V (Dell-Kuster 2020), applied to the laparoscopic phase. In parallel and independently of the video assessment, postoperative complications occurring within 30 days are graded by the principal investigator using the Clavien-Madadi classification from routine clinical follow-up data. No automatic conversion between complication classification systems is performed. Relationship to Institutional ERAS Care The department applies a 20-item Enhanced Recovery After Surgery (ERAS) protocol as routine care for all children undergoing appendectomy, independently of this study. Protocol adherence and recovery data (including time to medical readiness for discharge) are therefore documented for all participants as part of routine care, and are used in this study only as exploratory secondary variables. Enrollment in any other study is neither an inclusion criterion nor a requirement for participation in this study. Statistical Approach Inter-rater reliability is assessed with Gwet's AC1 as the primary measure, with weighted Kappa and the intraclass correlation coefficient reported as supporting measures. As a pre-specified sensitivity analysis, AC1 is additionally computed in the subset of videos with at least one identified intraoperative adverse event; if this subset comprises fewer than 15 videos, the subset analysis is reported descriptively only. Event incidence is reported with Wilson score confidence intervals. Exploratory hypotheses are analyzed with logistic regression (ERAS protocol adherence) and Spearman rank correlation (time to medical readiness for discharge; Clavien-Madadi severity). No adjustment for multiple testing is applied, as these analyses are explicitly exploratory; effect sizes with 95% confidence intervals are emphasized over p-values. Missing data are managed with a pre-specified, proportion-dependent three-scenario strategy. Statistical analysis is conducted under the responsibility of the principal investigator. Sample Size A target of 80 patients is based on published precedent for reliability pilot studies rather than on a confirmatory power calculation. This sample supports estimation of AC1 with acceptable precision (approximately +/-0.10 around an expected AC1 of 0.65) but does not provide statistical power for confirmatory hypothesis testing; secondary results are therefore reported as effect-size estimates. Known Limitations The single-surgeon, single-center design limits generalizability and is a deliberate pilot choice. Findings are restricted to non-complicated appendicitis and cannot be extrapolated to other pediatric procedures. Video-based assessment may under-detect anesthesia-related and organizational events. Post-hoc exclusion of conversion cases lowers the estimated incidence of high-grade events. The hybrid ClassIntra/Clavien-Madadi structure has not previously been tested in a pediatric population, so no accuracy benchmark exists. Accordingly, this study provides feasibility evidence, not validity evidence; multicenter studies are required for the latter.
Study Type
OBSERVATIONAL
Enrollment
80
Laparoscopic appendectomy performed as standard institutional care for non-complicated acute appendicitis. The study assigns no intervention: the procedure is routine care, and its operative video is recorded and independently graded for intraoperative adverse events during the laparoscopic phase.
Erciyes University Faculty of Medicine, Department of Pediatric Surgery
Kayseri, Kayseri, Turkey (Türkiye)
RECRUITINGInter-Rater Reliability of ClassIntra Grading (Key Feasibility Indicator)
Agreement between two independent, blinded pediatric surgeon raters on the ClassIntra severity grade assigned to the laparoscopic phase of each operation, quantified with Gwet's AC1. The pre-specified feasibility threshold is AC1 \>= 0.60. Weighted Kappa and the intraclass correlation coefficient are reported as supporting measures. As a pre-specified sensitivity analysis, AC1 is additionally computed in the subset of videos with at least one identified intraoperative adverse event, since agreement on event-free cases is expected to be high and uninformative about grading discrimination. This is the key indicator of the feasibility profile; the three feasibility criteria are reported separately as progression criteria and are not combined into a composite rule.
Time frame: Intraoperative period (laparoscopic phase of each operation); reliability computed across the evaluable cohort at database lock, approximately 10 months after study start.
Applicable Coverage of ClassIntra (Supporting Feasibility Indicator)
Proportion of enrolled cases that cannot be graded with ClassIntra by the raters, for any reason including insufficient video quality or incomplete assessment. The pre-specified feasibility threshold is a non-assessable proportion below 5%. Reported as a proportion with a 95% confidence interval, together with the reason for each non-assessable case.
Time frame: Intraoperative period (laparoscopic phase of each operation); computed across the enrolled cohort at database lock, approximately 10 months after study start.
Discriminative Capacity of ClassIntra (Supporting Feasibility Indicator)
Number of distinct ClassIntra severity grades (of the five possible grades, I to V) represented in the study cohort. The pre-specified feasibility threshold is representation of at least three of the five grades. The full grade distribution is additionally reported descriptively. No entropy or dispersion threshold is applied.
Time frame: Intraoperative period (laparoscopic phase of each operation); computed across the evaluable cohort at database lock, approximately 10 months after study start.
Incidence of Intraoperative Adverse Events
Proportion of operations in which at least one intraoperative adverse event is identified by the raters during the laparoscopic phase, reported as a point estimate with a Wilson score 95% confidence interval.
Time frame: Intraoperative period (laparoscopic phase of each operation).
Distribution of Intraoperative Adverse Events by Event Type, Mechanism and Severity
Descriptive frequency map of all identified intraoperative adverse events across three levels: event type (E1 bleeding, E2 thermal injury, E3 avulsion, E4 serosal tear, E5 injury to adjacent organ, E6 detached clip, E7 spillage), mechanism (M1 excessive force or distance, M2 insufficient force or distance, M3 wrong orientation, M4 insufficient visualization), and ClassIntra severity grade (I to V). Events that cannot be assigned a mechanism are reported in a separate category.
Time frame: Intraoperative period (laparoscopic phase of each operation).
Association Between Intraoperative Event Severity and Institutional ERAS Protocol Adherence (Exploratory)
Association between the presence of at least one ClassIntra Grade II or higher intraoperative adverse event and adherence to the institution's routine 20-item Enhanced Recovery After Surgery protocol, analyzed with logistic regression and reported as an odds ratio with a 95% confidence interval. Adherence data are obtained from routine clinical records, as the protocol is applied to all patients as standard care. This analysis is exploratory and hypothesis-generating; no adjustment for multiple testing is applied.
Time frame: Index hospitalization, from admission to actual discharge (typically up to 72 hours).
Association Between Intraoperative Event Severity and Time to Medical Readiness for Discharge (Exploratory)
Correlation between ClassIntra severity grade and the time from arrival in the post-anesthesia care unit until documented medical readiness for discharge, analyzed with Spearman rank correlation and reported as a correlation coefficient with a 95% confidence interval. Exploratory and hypothesis-generating.
Time frame: From arrival in the post-anesthesia care unit until medical readiness for discharge, typically up to 48 hours.
Association Between Intraoperative Event Severity and Postoperative Complication Severity (Exploratory)
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Correlation between ClassIntra severity grade assigned from the operative video and Clavien-Madadi grade of postoperative complications occurring within 30 days, assigned independently by the principal investigator from routine clinical follow-up data. Analyzed with Spearman rank correlation and a cross-tabulation, reported with a 95% confidence interval. Exploratory and hypothesis-generating; this is the first such analysis reported in a pediatric population.
Time frame: 30 days after surgery.