Validation of the Clavien-Madadi Classification for Unexpected Events in Pediatric Surgery: A Collaborative ERNICA Project.

BACKGROUND: The Clavien-Madadi classification is a novel instrument for the assessment and grading of unexpected events in pediatric surgery, based on the Clavien-Dindo classification. The system has been adjusted to better fit the pediatric population in a prospective single-center study. There is a need now to validate the Clavien-Madadi classification within an international expert network. METHODS: A pediatric surgical working group created 19 case scenarios with unexpected events in a multi-staged process. Those were circulated within the European Reference Network of Inherited and Congenital Anomalies (ERNICA) and surgeons were instructed to rate the scenarios according to the Clavien-Madadi vs. Clavien-Dindo classification. RESULTS: 59 surgeons from 12 European countries completed the questionnaire. Based on ratings of the case scenarios, the Clavien-Madadi classification showed significantly superior agreement rates of the respondents (85.9% vs 76.2%; p < 0.05) and was less frequently considered inaccurate for rating the pediatric population compared to Clavien-Dindo (2.1% vs 11.1%; p = 0.05). Fleiss' kappa analysis showed slightly higher strength of agreement using the Clavien-Madadi classification (0.74 vs 0.69). Additionally, intraclass correlation coefficient was slightly higher for the Clavien-Madadi compared to the Clavien-Dindo classification (ICCjust 0.93 vs 0.89; ICCunjust 0.93 vs 0.89). More pediatric surgeons preferred the Clavien-Madadi classification for the case scenarios (43.0% vs 11.8%; p = 0.002) and advantages of the Clavien-Madadi were confirmed by 81.4% of the surgeons. CONCLUSION: The Clavien-Madadi classification is an accurate and reliable instrument for the grading of unexpected events in pediatric surgery. We therefore recommend its application in clinical and academic pediatric surgical practice. LEVEL OF EVIDENCE: III.

Benchmarks for Pediatric Surgical Registries: Recommendations for the Assessment and Grading of Complications.

Procedure-related registries in general surgical practice offer a platform for prospective trials, the pooling of data, and detailed outcome analysis. Recommendations by the Idea, Development, Exploration, Assessment, and Long-term follow-up (IDEAL) collaboration and Outcome4Medicine have further improved the uniform reporting of complications and adverse events.In the pediatric surgical network, disease-specific registries for rare and inherited congenital anomalies are gaining importance, fostering international collaborations on studies of low-incidence diseases. However, to date, reporting of complications in the pediatric surgical registries has been inconsistent. Therefore, the European Reference Network for Rare Inherited and Congenital Anomalies (ERNICA) recently endorsed the validation of the first severity grading system for children. The planned reform of the European Paediatric Surgical Audit (EPSA) registry, which includes the implementation of the Clavien-Madadi classification, represents a further effort to establish uniform outcome reporting.This article provides an overview of experiences with surgical registries and complication reporting, along with the potential application of this knowledge to future pediatric surgical practice.

Titanium nitride coating of pectus bar increases metal contamination after minimally-invasive repair of pectus excavatum.

INTRODUCTION: Previous studies demonstrated a release of toxic metals, e.g. nickel and chromium, from stainless steel bars used for minimally invasive repair of pectus excavatum (MIRPE). In the present study, we investigated the impact of titanium nitride coating on the metal release and exposure of MIRPE patients. MATERIAL AND METHODS: We analyzed the courses of nickel and chromium levels in blood, urine and local tissue in patients undergoing MIRPE with a titanium nitride coated pectus bar between 03/2017 and 10/2018. Sample collection was scheduled prior to MIRPE, at defined postoperative time points and at bar removal. Additionally, we evaluated irritative symptoms. Results were compared to a control group who received uncoated stainless steel bars in a previous time period (03/2015-02/2017). RESULTS: 12 patients received coated pectus bars (mean age 15.7 years). The control group included 28 patients. After implantation of a titanium nitride coated bar, significant increase in systemic nickel and chromium levels after one, two and three years was noted. In an interim analysis one year after MIRPE, we observed patients with coated bars to have significantly elevated trace metal values compared to the control group. This elevation persisted throughout the observation period. Tissue metal values were also significantly increased. Irritative symptoms occurred significantly more often in study patients compared to controls (50.0% vs. 14.3%). CONCLUSIONS: Coating of pectus bars with titanium nitride failed to reduce metal contamination after MIRPE. Instead, it resulted in a significant increase of trace metal levels after MIRPE, compared to patients with stainless steel bars, which may be explained by wear of the coating and inter-component mobilization processes.

Implementation and validation of a novel instrument for the grading of unexpected events in paediatric surgery: Clavien-Madadi classification.

BACKGROUND: Inconsistent definitions of complications and unexpected events have limited accurate analysis of surgical outcomes. Perioperative outcome classifications currently used for adult patients have limitations when used for children. METHODS: A multidisciplinary group of experts modified the Clavien-Dindo classification to increase its utility and accuracy in paediatric surgery cohorts. Organizational and management errors were considered in the novel Clavien-Madadi classification, which focuses on procedural invasiveness rather than anaesthetic management. Unexpected events were prospectively documented in a paediatric surgery cohort. Results of the Clavien-Dindo and Clavien-Madadi classifications were compared and correlated with procedure complexity. RESULTS: Unexpected events were prospectively documented in a cohort of 17 502 children undergoing surgery between 2017 and 2021. The results of both classifications were highly correlated (ρ = 0.95), although the novel Clavien-Madadi classification identified 449 additional events (organizational and management errors) over the Clavien-Dindo classification, increasing the total number of events by 38 per cent (1605 versus 1158 events). The results of the novel system correlated significantly with the complexity of procedures in children (ρ = 0.756). Furthermore, grading of events > grade III according to the Clavien-Madadi classification showed a higher correlation with procedure complexity (ρ = 0.658) than the Clavien-Dindo classification (ρ = 0.198). CONCLUSION: The Clavien-Madadi classification is a tool for the detection of surgical and non-medical errors in paediatric surgery populations. Further validation in paediatric surgery populations is required before widespread use.

Definition, Documentation, and Classification of Complications in Pediatric Surgical Literature-A Plea for Standardization.

Severity grading systems for complications in surgical patients have been used since 1992. An increasing assessment of these instruments in pediatric surgery is also noticed, without their validation in children. To analyze the current practice, we performed a literature review with focus on the assessment and grading of complications. The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Studies reporting on postoperative complications as a primary or secondary endpoint using a severity grading system were included. Definition for simple adverse events, classification systems used, and the time horizon of postoperative documentation were analyzed. A total of 566 articles were screened, of which 36 met the inclusion criteria. About 86.1% of the papers were retrospective and 13.9% prospective analyses. None of the studies were prospective-randomized trials. Twenty (55.6%) studies did not include a definition of adverse events, whereas the remaining 16 (44.4%) showed variations in their definitions. All studies applied the Clavien-Dindo classification, whereas five (13.9%) additionally used the Comprehensive Complication Index. One study compared alternative grading instruments with the Clavien-Dindo classification, without demonstrating the superiority of any classification in pediatric surgery. Twenty-two studies (61.1%) did not report the time horizon of perioperative complication documentation, while 8 studies (22.2%) used 30 days and 6 studies (16.7%) used 3 months of postoperative documentation. Definition and classification of postoperative complications are inconsistent in the pediatric surgical literature. Establishment of a standardized protocol is mandatory to accurately compare outcome data.

Pleural CD14+ monocytes/macrophages of healthy adolescents show a high expression of metallothionein family genes.

Nowadays laparoscopic interventions enable the collection of resident macrophage populations out of the human cavities. We employed this technique to isolate pleural monocytes/macrophages from healthy young adults who underwent a correction of pectus excavatum. High quality CD14+ monocytes/macrophages (plMo/Mφ) were used for RNA-sequencing (RNA-seq) in comparison with human monocyte-derived macrophages (MDM) natural (MDM-0) or IL-4-polarized (MDM-IL4). Transcriptome analysis revealed 7166 and 7076 differentially expressed genes (DEGs) in plMo/Mφ relative to natural MDM-0 and polarized MDM-IL4, respectively. The gene set enrichment analysis, which was used to compare RNA-seq data from plMo/Mφ with single-cell (scRNA-seq) data online from human bronchial lavage macrophages, showed that plMo/Mφs are characterized by a high expression of genes belonging to the metallothionein (MT) family, and that the expression of these genes is significantly higher in plMo/Mφ than in MDM-0 or MDM-IL4. Our results provide additional insights on high MTs-expressing macrophage subsets, which seem to be present not only in bronchial lavage of healthy adults or in pleural exudates of lung cancer patients but also in pleural fluid of healthy young adults. Macrophage subsets expressing high MTs may have specific roles in lung defense, repair, and homeostasis, and require further investigations.

Nickel contamination after minimally-invasive repair of pectus excavatum persists after bar removal.

BACKGROUND: Minimally-invasive repair of pectus excavatum (MIRPE) has been shown to be associated with high release of trace metals into patient's body. The aim of our study was to analyze the kinetics of metal contamination after MIRPE and after bar removal. METHODS: We prospectively assessed nickel and chromium changes in blood, urine, and local tissue in patients undergoing MIRPE with stainless-steel bar(s). Baseline samples were taken prior to surgery, further samples were taken at six defined time points until 30 months after bar removal. Clinical symptoms were evaluated at the time of every sample collection. RESULTS: 28 patients were included (mean age 16.4 years). At four weeks after MIRPE and persisting up to bar removal, we found significantly elevated trace metal levels in blood and urine. Tissue nickel and chromium levels were significantly elevated at the time of bar removal. After bar removal, the concentration of trace metal in urine and the concentration of chromium in plasma decreased gradually. In contrast, nickel levels in blood further increased. Five patients showed irritative symptoms after MIRPE, all symptomatic patients had elevated metal levels. CONCLUSIONS: Following MIRPE, we found a rapid systemic increase of nickel and chromium. Our data indicate that trace metal release could cause irritative symptoms. The prolonged elevated systemic nickel levels beyond bar removal necessitate further investigations of the long-term side effects of MIRPE.

The Role of Laparoscopic Treatment of Choledochal Malformation in Europe: A Single-Center Experience and Review of the Literature.

BACKGROUND: Numerous studies from Asian countries, including large collectives, have reported excellent results after laparoscopic resection of choledochal malformation (CM). However, the role of laparoscopic CM resection is still controversial outside Asia. We aimed to analyze the outcome of laparoscopic CM resection in our institution and to compare our outcome with the data reported in the literature. METHODS: All patients who underwent laparoscopic CM resection in our pediatric surgical department from 2002 to 2019 were retrospectively analyzed for surgical details and postoperative complications, which were graded according to the Clavien-Dindo classification. A systematic literature search identified all reports on over 10 cases of laparoscopic pediatric CM resection and surgical details, follow-up, and complication rates were extracted. RESULTS: Fifty-seven patients (72% female) with a mean age of 3.6 + 4.1 years underwent laparoscopic CM resection in our department. Conversion rate was 30%. Total complication rate was 28%. The rate of major complications (Clavien-Dindo grade III or more) was 16% and included stricture of the biliodigestive or enteric anastomosis (n = 4), adhesive ileus (n = 3), portal vein thrombosis (n = 1), and recurrent cholangitis with consecutive liver transplantation (n = 1). With increasing experience, complication rates decreased. The majority of publications on laparoscopic CM resections originated from Asia (n = 36) and reported on low complication rates. In contrast, publications originating from non-Asian countries (n = 5) reported on higher complications following laparoscopic CM resection. CONCLUSION: Our data indicate that laparoscopic CM resection can be safely performed. The learning curve in combination with the low incidence calls for a centralization of patients who undergo laparoscopic CM resection. There seems to be a discrepancy on complications rates reported from Asian and non-Asian countries following laparoscopic CM resection.

Factors of family impact in a Swedish-German cohort of children born with esophageal atresia.

BACKGROUND: After repair of esophageal atresia (EA), childhood survivors commonly present with digestive and respiratory morbidity, and around 55% have associated anomalies. Although it is known that these problems can reduce health-related quality of life in children with EA, less is understood about the impact on the family. We aimed to identify factors related to family impact in children with EA. METHODS: One parent each of a child with EA (2-18 years) in 180 families from Sweden and Germany answered the PedsQL™ Family Impact Module as the dependent variable. The independent variables were the child's parent-reported health-related quality of life as measured by PedsQL™ 4.0, current symptoms, school situation, and parent/family characteristics together with child clinical data from the medical records. RESULTS: Stepwise multivariable regression analysis showed a multifactorial model of the total family impact scores (R2 = 0.60), with independent factors being the child's overall generic health-related quality of life, school-absence ≥ 1/month, severe tracheomalacia, a family receiving carer's allowance, and a parent with no university/college education, p < 0.05. Logistic regression analysis showed that an increased number of symptoms in the child the preceding 4 weeks lowered the family impact scores; however, the child's feeding (R2 = 0.35) and digestive symptoms (R2 = 0.25) explained more in the variation of scores than the child's respiratory symptoms (R2 = 0.09), p < 0.0001. CONCLUSIONS: Family functioning may be a contributing factor to the maintenance of child health. The study findings suggest multifactorial explanations to family impact in children with EA, which are essential when optimizing the support to these families in clinical and psychosocial practice. Future research should explore experiences of family impact from all family members' perspectives and multicenter studies are warranted to understand better the effectiveness of psychosocial-educational interventions to families of children with EA.

Analysis of Pulmonary Surgery in Children and Adolescents in Germany: Who Is doing What?

INTRODUCTION: In Germany, pediatric surgery is organized in a decentralized manner. A nationwide clinical registry does not exist. The aim of this research is to analyze the current status of pulmonary surgery in the country in respect of children and adolescents. MATERIALS AND METHODS: Claims data have been extracted from two health insurance databases representing 34% of the German population. Operative diagnoses and procedures, as well as patients' characteristics, were recorded from 2016 to 2019. RESULTS: The incidence of the four index diagnoses investigated matched the current literature in three of four entities. The main indications <8 years were congenital lung malformations (61%) and spontaneous pneumothorax at age 8 to 17 years (77%). Furthermore, 1,668 pediatric pulmonary procedures (0-17 years) were identified (668 pulmonary resections). Two age peaks were identified: 13% of patients were operated on before 1 year old and 50% of patients were between 15 and 17 years old. Video-assisted-thoracoscopic-surgery (VATS) for pulmonary resections was applied in 62% of cases. 96% of pulmonary resections in patients <1 year and 70% of pulmonary resections in children between 1 and 14 years were performed by pediatric surgeons. Of patients between 15 and 17 years old, only 14% were operated on in pediatric surgery. The estimated average pulmonary resection caseload was 3.2 cases per year and per institution for pediatric surgery and 1.5 for adult surgery. CONCLUSION: Indications for pulmonary surgery in children arise from rare diagnoses. In total, 66% of lung resections are performed in patients <1 year and >14 years. The majority of lung resections are performed as VATS. Patients ≤14 years are predominantly operated on by pediatric surgeons. The accessibility of pediatric pulmonary surgery is acceptable, but there is a low caseload per center.

Appendiceal Carcinoids in Children-Prevalence, Treatment and Outcome in a Large Nationwide Pediatric Cohort.

Background and Objectives: Appendiceal carcinoids are rare neuroendocrine tumors and mainly found incidentally during histopathological examination following appendectomy. This observational cohort study was performed to determine the prevalence, treatment modalities and outcomes in children diagnosed with an appendiceal carcinoid tumor. Materials and Methods: Data from the largest German statutory health insurance "Techniker Krankenkasse" were analyzed within an 8-year period: January 2010 to December 2012 and January 2016 to December 2020. Patient characteristics, surgical technique, type of surgical department, diagnostic management, and postoperative morbidity were analyzed. Results: Out of 40.499 patients following appendectomy, appendiceal carcinoids were found in 44 children, resulting in a prevalence of 0.11%. Mean age at appendectomy was 14.7 (±2.6) years. Laparoscopic approach was performed in 40 (91%) cases. Right-sided hemicolectomy was performed in 8 (18%) patients. Additional diagnostic work-up (CT and MRI) was recorded in 5 (11%) children. Conclusions: This large nationwide pediatric study shows that 1 in 1000 patients was found to have a neuroendocrine tumor of the appendix (prevalence 0.11%), emphasizing its low prevalence in the pediatric age group. The majority of patients were treated with appendectomy only. However, treatment modalities are still variable. Longer follow-up analyses are needed to evaluate published guidelines and recommendations to aim for a limited surgical approach.

Adjuvant Therapy with Budesonide Post-Kasai Reduces the Need for Liver Transplantation in Biliary Atresia.

Based on the hypothesis that autoimmunological factors coregulate the pathomechanism in biliary atresia (BA), adjuvant therapy with steroids has become routine, although its efficacy has never been proven. In 2010, a study on the advantages of budesonide compared to prednisolone in autoimmune hepatitis gave rise to experimental therapy using budesonide as an adjuvant BA treatment. Ninety-five BA patients prospectively received a budesonide 2 mg/dose rectal foam daily for three months (SG). A case-matched control group (CG: 81) was retrospectively recruited. The outcome measures were survival with native liver (SNL), determined at six months and two years after the Kasai procedure. The follow-up rate was 100%. At six months, SNL was statistically not different but became so after two years (SG: 54%; CG: 32%; p < 0.001). No steroid-related side effects were observed, except for eight patients with finally caught-up growth retardation. This study demonstrates for the first time a significantly longer survival with native liver in patients with BA after adjuvant therapy. However, indication, dosage, and duration of any budesonide application is not given in neonates with BA. Hence, we suggest extending the postoperative use of budesonide in a multicenter observational study with a clearly defined follow-up protocol, particularly in terms of potentially underestimated side effects.

Lack of gamma delta T cells ameliorates inflammatory response after acute intestinal ischemia reperfusion in mice.

T-cells have been demonstrated to modulate ischemia-reperfusion injury (IRI) in the kidney, lung, liver, and intestine. Whereas most T-cell subpopulations contribute primarily to the antigen-specific effector and memory phases of immunity, γδ-T-cells combine adaptive features with rapid, innate-like responses that can place them in the initiation phase of immune reactions. Therefore, we aimed to clarify the role of γδ-T-cells in intestinal IRI. Adult wild-type (WT) and γδ-T-cell-deficient mice were subjected to acute intestinal IRI. Gene expression of pro-inflammatory cytokines and influx of leukocyte subpopulations in the gut were assessed by qPCR and flow cytometry. Serum transaminases were measured as an indicator of distant organ IRI. Intestinal IRI led to increased influx of neutrophils, pro-inflammatory cytokine expression and LDH/ALT/AST elevation. Selective deficiency of γδ-T-cells significantly decreased pro-inflammatory cytokine levels and neutrophil infiltration in the gut following IRI compared to controls. Furthermore, γδ-T-cell deficiency resulted in decreased LDH and transaminases levels in sera, indicating amelioration of distant organ injury. Increasing evidence demonstrates a key role of T-cell subpopulations in IRI. We demonstrate that γδ-T-cell deficiency ameliorated pro-inflammatory cytokine production, neutrophil recruitment and distant organ injury. Thus, γδ-T-cells may be considered as mediators contributing to the inflammatory response in the acute phase of intestinal IRI.

Incidence of complications, organizational problems, and errors: Unexpected events in 1605 patients.

PURPOSE: Besides surgical complications, a variety of adverse events may affect patients' comfort and outcome. The purpose of this prospective study was to identify the incidence and impact of all unexpected events in pediatric surgical patients. METHODS: All unexpected events that occurred in our department during the period of February 2017-July 2018 were prospectively assessed. Complications associated with surgery, non-surgical treatment, errors and organizational problems were included. Events were classified using a modified version of Clavien-Dindo. Sentinel events were defined as death, serious injury, or the risk thereof (grade IV-V). Organizational events were analyzed separately. All events were discussed during morbidity and mortality-conferences, and the results and measures were documented. RESULTS: Unexpected events occurred in 297 of 1605 patients (18.5%), of whom 1124 (70%) had undergone surgery. More than half of all events were not associated with an operation (n=237; 54%). The severity of all events was mostly minor (grade I-IIIb; n=410; 94%). Twenty-eight sentinel events (IV-V) occurred (6% of all events). Twenty-two (2%) patients died; however, none of these deaths were related to surgery. The top 5 events included organizational problems in 78 instants (18%), wound healing disorders in 44 (10%), recurrence of initial problems in 36 (8%), dislocation of indwelling catheters in 26 (6%) and bleeding in 16 (4%). Errors were identified in 15 patients (3%). We derived 10 changes of concepts of management or treatment. CONCLUSION: The incidence of unexpected events in pediatric surgical patients is high when complications associated with surgical and non-surgical treatment and organizational alterations are documented prospectively. In our study, most events were minor and did not substantially affect patients' outcomes. Prospective assessment helped to identify organizational shortcomings and develop preventive strategies.

Vacuum-assisted closure (VAC) prevents wound dehiscence following posterior sagittal anorectoplasty (PSARP): An exploratory case-control study.

BACKGROUND: Wound dehiscence (WD) of the anocutaneous anastomosis or perineal body after posterior sagittal anorectoplasty (PSARP) is common. We aimed to evaluate the efficacy of a perineal vacuum-assisted closure (VAC) for prevention of WD following repair of anorectal malformations (ARM) with rectoperineal and rectovestibular fistula. METHODS: A retrospective dual-center case-control study of children undergoing PSARP without colostomy between 2011 and 2019 was performed. The VAC group received preoperative bowel preparation (PBP), postoperative application of a VAC, loperamide (only Location A), intravenous antibiotics (IA), and total parenteral nutrition (TPN). The non-VAC group underwent PBP, loperamide (Location A), IA, and TPN without VAC. Primary outcome was WD at the anocutaneous anastomosis or reconstructed perineal body within the first 14 days after surgery. RESULTS: The study population included 18 patients (VAC group) and 20 children (non-VAG group) with rectoperineal and rectovestibular fistula. The incidence of WD in the VAC group was 0% compared to 25% in the non-VAC group (0/18 vs. 5/20, p = 0.04). No VAC related complications occurred. CONCLUSION: Postoperative application of a VAC embedded in a perioperative treatment protocol has the potential to prevent wound dehiscence of the neoanus and reconstructed perineal body following PSARP. TYPE OF STUDY: Case-control study. LEVEL OF EVIDENCE: Level III.

Ethical Publication Standards in Articles Reporting on Novel Surgical Methods: Analysis of Three Pediatric Surgical Journals.

INTRODUCTION: According to the Declaration of Helsinki, medical research and new therapeutic interventions involving human subjects require prior informed consent and ethical approval. In 2010, 46% of pediatric surgical publications lacked documentation of ethical approval and 84% lacked documentation of informed parental consent with lowest rates of ethical adherence found in articles concerning novel methods. The aim of this study was to investigate whether adherence to ethical standards has improved in pediatric surgical publications. MATERIALS AND METHODS: All 3,093 consecutive articles published in Journal of Pediatric Surgery, European Journal of Pediatric Surgery, and Pediatric Surgery International over the last 5 years were systematically reviewed for publications describing novel surgical methods. Novel methods were defined as surgical methods not published before or not considered common practice. The publications were reviewed as to whether ethical approval and informed consent to participate was documented. RESULTS: In total, 105 articles describing novel surgical methods were identified (61 Journal of Pediatric Surgery, 16 European Journal of Pediatric Surgery, and 28 Pediatric Surgery International). Authors reported on new operative techniques (62%), modified techniques (31%), or use of new materials (7%). Ethical approval was documented in 52% of the articles with almost half reporting approval for retrospective data analysis only but not the application of the novel method. Informed consent was documented in 21% of publications. Complications were reported in 48% of the studies, including recurrences and reinterventions for the unsuccessful novel methods. Two authors reported mortalities due to underlying disease, one of which failed to report prior ethical approval or informed consent. CONCLUSION: Adherence to ethical publication principles in pediatric surgery has improved over the last years but is still lacking in many publications. When implementing new methods, prior ethical approval and informed consent and their documentation are mandatory, specifically in the light of potential hazard to patients.

Phenotypic Switch of Human Peritoneal Macrophages during Childhood.

INTRODUCTION: Human peritoneal macrophages are resident in the abdominal cavity where they support the specific microenvironmental regulation. We have previously observed a phenotypic switch of murine macrophages during infancy that was associated with a functional development. To investigate the age related changes in human peritoneal macrophages, we analyzed peritoneal macrophages of children undergoing laparoscopic procedures. MATERIALS AND METHODS: Immunologically healthy children who received minimally invasive surgery in our department were included in this study. In all cases, the written consent was obtained. At the beginning of laparoscopy, physiologic NaCl-solution was instilled and manually removed through the umbilical trocar to gain macrophages. Lavage cells were processed for flow cytometry analysis. CD14+ myeloid cells were monitored for specific lineage marker expression. RESULTS: A total of 21 donors (age: 7 days-18 years) were included and divided into three groups. In all age groups, 97% of myeloid cells expressed CD11b. 70% of these expressed CD14. Three subsets of CD14 cells were detected on the basis of CD14/CD16 expression (CD14 + CD16dim, CD14 + CD16inter, and CD14 + CD16high). In neonates, >80% belonged to the CD14 + CD16high subset, reducing to 30% in adolescents. In none of the cases, the M2 markers CD23 and CD25 were expressed. CONCLUSION: This is the first study showing that lineage marker expression of peritoneal macrophages in neonates differs from that in adults. The knowledge about neonatal tissue resident macrophages might help to understand their complex interaction and to use specific macrophage properties for therapeutic approaches.