Biomarkers for Early Detection of Postoperative Intra-Abdominal Abscess in Children with Perforated Appendicitis

Background/Objectives: Appendicitis is a common pediatric surgical emergency, with perforation leading to significant complications such as intra-abdominal abscesses. Current diagnostic methods are not sufficiently investigated in terms of timeliness, which emphasizes the need for reliable, non-invasive biomarkers for early signaling of postoperative abscess formation. This study aims to evaluate the associations between laboratory markers and postoperative intra-abdominal abscess formation in children treated for perforated appendicitis. Methods: This study retrospectively analyzed records of children treated for acute perforated appendicitis over ten years to identify differences in blood variables and clinical, radiological, and surgical factors between those who developed postoperative intra-abdominal abscesses and those who did not. Results: A total of 206 patients met the inclusion criteria. Of these, 30 developed an intra-abdominal abscess. Of the preoperative clinical factors, only rebound tenderness was significantly more present in the group that developed an abscess. Between the observed groups, leukocytes and neutrophils showed significant higher results in the group that developed an abscess at all observed time points, while C-reactive protein (CRP) showed a significant difference from the 4th postoperative day onwards. Neutrophil-to-lymphocyte ratio (NLR), neutrophil-to-monocyte ratio (NMR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII) and systemic inflammatory response index (SIRI) were significantly higher after 72 h, while SIRI showed a significant difference already after 24 h, and NLR and SII already within 24 h postoperatively. NLR and SIRI showed a significant mean percentage increase between samples taken on days 2 and 3 compared to samples taken on days 4 and 5. CRP showed a significantly smaller mean percentage decrease during this interval, as well as in the interval between samples taken on days 4 and 5, compared to samples taken on days 6 and 7. Looking at the preoperative variables of interest, neutrophil percentage was the only significant predictor. Because these serial postoperative comparisons were not corrected for multiple testing, they should be interpreted as exploratory rather than confirmatory. Conclusions: Blood biomarkers demonstrate significant postoperative changes within the early postoperative period that are associated with intra-abdominal abscess formation in children treated for perforated appendicitis.