Diagnostic and therapeutic yield of postoperative imaging after complicated appendicitis: a western pediatric surgery research consortium prospective study.

PURPOSE: While laparoscopic appendectomy is the standard of care for acute appendicitis, postoperative imaging practices for complicated cases remains variable, and abscesses are a frequent source of morbidity. Postoperative imaging variation may influence the timing of abscess diagnosis and intervention. This study examines the association between postoperative imaging timing and both diagnostic yield (abscess detection) and therapeutic yield (intervention rate), recognizing that detection of an abscess on imaging does not always result in intervention.

METHODS: We conducted a prospective study of children with complicated appendicitis across nine children's hospitals (2022-2024). Patients were stratified by postoperative day (POD) of first imaging (US/CT/MRI). Primary outcomes were diagnostic yield of imaging for abscess formation and therapeutic yield for drainage or reoperation. We performed multivariable logistic regression to examine the association of POD windows and yield. Pairwise comparisons of marginal predicted probabilities were obtained with post-estimation margins and delta-method standard errors.

RESULTS: Among 2,560 patients with complicated appendicitis, 578 (22.5%) underwent postoperative abdominal imaging. Of these, 327 (56.6%) occurred prior to discharge and 251 (43.4%) after discharge. Therapeutic yield varied as a continuous function of postoperative day; LOWESS analysis demonstrated increasing probability of drainage through approximately POD7-10 followed by decline, with sliding window analysis identifying peak therapeutic yield between POD6-8 (42.3% of scans resulted in drainage). Diagnostic yield was highest when imaging occurred before POD10, while imaging after POD10 identified significantly fewer abscesses (37.2% vs. 69.2%, p < 0.001) and resulted in fewer interventions (20.0% vs. 37.2%, p < 0.001). When stratified by discharge status, pre-discharge therapeutic yield peaked between POD6-10, while post-discharge yield plateaued around POD6-8. Therapeutic yield was higher among patients imaged before discharge, who represent a clinically distinct population with persistent failure to meet discharge criteria.

CONCLUSION: Postoperative imaging performed before POD10 demonstrated the highest diagnostic and therapeutic yield for detecting intra-abdominal abscess following appendectomy for complicated appendicitis. Therapeutic yield for postoperative imaging peaked between POD 6-8. Imaging performed after POD10 was significantly less likely to identify drainable collections. Among patients who re-present after discharge, imaging yield declines after POD10, which may inform the timing and modality of imaging in this population, balancing diagnostic utility against radiation exposure. Diagnosing an abscess does not always lead to intervention; clinicians should prioritize the POD6-8 window to maximize actionable yield.